Improving Understanding and Prediction of Warm Season ... - CiteSeerX

A Proposal to the National Oceanic and Atmospheric Administration in Support of the Collaborative Science, Technology, and Applied Research (CSTAR) Program

Improving Understanding and Prediction of Warm Season Precipitation Systems in the Southeastern and Mid-Atlantic Regions From: Department of Marine, Earth, and Atmospheric Sciences North Carolina State University Starting Date: 1 May 2007 Requested Funding: $375,000 Year 1: $125,000 Year 2: $125,000 Year 3: $125,000

Principal Investigators:

Department Head:

____________________ Gary M. Lackmann+ Associate Professor (919) 515-1439

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_________________ Lian Xie Professor (919) 515-1435

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Institutional Representative: Associate VC for Research Admin 2701 Sullivan Drive Administrative Bldg. III, Suite 240 Raleigh, NC 27695-7514 (919) 513-2148

____________________ Matt Parker+ Assistant Professor (919) 513-4367 +

Department of Marine, Earth, and Atmospheric Sciences North Carolina State University Raleigh, NC 27695-8208 Primary Contact: Gary M. Lackmann Department of Marine, Earth and Atmospheric Sciences North Carolina State University Box 8208 Raleigh, NC 27695-8208 phone: (919) 515-1439 fax: (919) 515-7802 e-mail: [email protected]

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Improving Understanding and Prediction of Warm Season Precipitation Systems in the Southeastern and Mid-Atlantic Regions North Carolina State University

Principal Investigators: Gary Lackmann, Lian Xie, and Matt Parker Total Proposed Cost: $375,000, Budget Period: 3 Years Abstract Applied research is proposed with the goal of improving understanding and prediction of a set of highimpact meteorological phenomena including landfalling tropical cyclones (TCs), convection, and orographically driven weather systems. The proposed research emphasis is upon warm-season phenomena, and reflects a broad consensus developed through discussions involving 10 National Weather Service Forecast Offices (NWSFO) and the Southeastern River Forecast Center (SERFC). Landfalling tropical cyclones (TCs) present a high-profile challenge to forecasters in the southeastern U.S. Priority areas identified by regional NWSFO include (i) prediction of tornadoes and tornadic environments associated with TCs with 0-24 h lead time, (ii) quantitative precipitation forecasting (QPF) and inland flooding, (iii) prediction of non-tornadic TC winds, and (iv) storm surge forecasting. Environments supporting TC tornadoes are distinct from those conducive to high-plains supercells, although common factors include the presence of dry air aloft, lower-tropospheric boundaries, and strong vertical wind shear. The proposed emphasis is upon improved anticipation in the 3-24 h time frame, in addition to the nowcasting aspect. Inland flooding associated with TCs has received previous attention; this research has revealed that low-level boundaries may exert a profound influence on the precipitation distribution, storm track, wind damage patterns, and even tornadic activity. Research aimed at improved anticipation of lower boundary occurrence and TC-boundary interactions will potentially aid prediction of all of these phenomena. An additional challenge accompanying landfalling TCs is the prediction of severe non-tornadic TC winds. It is hypothesized that the strength of vertical wind mixing exerts a first-order influence on surface wind speeds; this mixing can be inhibited in the stable airmass on the cool side of a lower-tropospheric boundary. Coastal flooding and storm surge research has advanced in recent years, however we seek to explore opportunities for improved anticipation of estuarine and river flooding, in addition to improved modeling of surge response to asymmetry in TC wind fields. Organized convection is responsible for a large proportion of severe weather occurrences across the region. Many of the conceptual models and forecasting tools utilized by operational forecasters are derived from studies of Midwestern convection; here, we propose to examine the character of convective systems in the eastern U.S. and study their interaction with topographic features such as the Appalachian Mountains. For example, when organized convective storms approach the Appalachians from the west, forecasters are faced with the task of determining whether the system will dissipate, maintain strength, or even possibly intensify as it crosses the mountains. The proposed research will determine which environmental factors control whether convective system decay or maintenance as the system crosses the Appalachian Mountains. Cold-air damming (CAD) exerts a well-known influence on the southeastern and Mid-Atlantic regions. Previous research has addressed several of the difficulties in the prediction of cool-season cold-air damming. However, the relevance of these findings to warm-season CAD is unknown. During warm-season events, solar (bottom-up) CAD erosion is likely more dominant, and the occurrence of convective storms at the periphery of the cold dome has been highlighted by forecasters as an important operational problem. Here we seek to define the environmental conditions that control the wedge front (boundary of CAD air mass) location, and determine what factors characterize events accompanied by severe convection at the periphery of the cold dome.

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RESULTS FROM PRIOR SUPPORT Two of the PIs on this proposal (Lackmann and Xie) have also served as PIs for two previous NC State CSTAR awards (in 2000 and 2003). We will here focus on the outcomes of these two previous awards, as this information is most relevant in assessing the merit of the current proposal. The 3rd PI, Dr. Parker, is relatively new to NC State. Owing to the fact that he was not involved in the previous NC State CSTAR efforts, information concerning the results of his prior support will focus on funding from other agencies. Title: Improving Forecasts of Topographically-Forced Weather Systems in the Carolinas and Virginia Period: 1 May 2000 - 31 August 2003; NOAA Grant NA07WA0206, Amount: $375,000 Principle Investigators: Riordan, Lackmann, Xie The objectives and accomplishments for this project centered around progress in scientific understanding of the physical processes governing Cold-Air Damming (CAD) erosion and Coastal Front (CF) movement, primarily during the cold season. Accomplishments also include applications of findings in the collaborative development of diagnostic methods and forecast guidelines. Scientific accomplishments and results: • Development of objective methods for identifying CAD and CF events, along with methods for differentiating major CAD/CF types based on physical processes, leading to the development of a representative climatology of CAD and CF events (Bailey et al. 2003, Wea. Forecasting) • Identification of key physical processes that govern CAD erosion and onshore CF movement (e.g., cold advection aloft is effective in eroding the CAD inversion; Stanton MS Thesis, 2004) • Determination that some CAD erosion scenarios are inherently more predictable (e.g., those characterized by a cold-frontal passage) than others (e.g., the northwest low category), and identification of limitations in model physics that may account for forecasts of premature CAD erosion in model forecasts, including overactive shallow mixing in the BMJ convective scheme and issues relating to cloud-radiation interactions (Stanton 2004). • Identification of a bias in the land-surface model used in the operational Eta (now NAM) model, and collaboration with NCEP scientists to correction it (Lackmann et al. 2002, Wea. Forecasting). Title: Improving Cold-Season Quantitative Precipitation Forecasting in the Southeastern United States Period: 1 June 2003 - 31 May 2006; NOAA Grant NA07WA0206, Amount: $375,000 Principle Investigators: Lackmann, Xie, Riordan The objectives and accomplishments for this project related to cold-season Quantitative Precipitation Forecasting (QPF). As with the previous CSTAR project, efforts here focused upon both pattern and process recognition as well as model experiments to determine physical process representation in the model atmosphere. One major component was investigation of the challenge of QPF in the presence of organized upstream convection. Scientific accomplishments and results: • Diagnosis of the physical mechanisms whereby upstream convection can alter northward moisture transport and precipitation in the downstream region; primary factors include (i) moisture removal and (ii) alteration of the low-level jet (LLJ) (Mahoney MS Thesis, Mahoney and Lackmann 2006b, Wea. Forecasting). • Elucidation of the role of upstream incipient precipitation (IP) in driving the westward extension of the precipitation shield in the 24-25 January 2000 East Coast storm, determination of the nature of the IP, and diagnosis of model inability to predict this feature (Brennan and Lackmann 2005, 2006a,b Mon. Wea. Rev.) • Identification of a slow bias in operational model representation of upstream MCS motion, and diagnosis (using WRF simulations for case-study events) of the causes for slow model movement of convective systems (Mahoney MS Thesis, Mahoney and Lackmann 2006b, Wea. Forecasting).

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• Documentation of both enhanced and reduced downstream QPF in the presence of upstream convection, depending on the speed of the upstream convection relative to the parent synoptic system. This is important because it shows a counter example to the conventional forecaster practice of QPF reduction when upstream convection is observed (Mahoney & Lackmann 2006b). • Sensitivity studies of the representation of the coastal front and offshore cyclogenesis to choice of model convective parameterization (Mahoney and Lackmann 2006a, Wea. Forecasting) • Documentation of different CAD erosion scenarios and observed precipitation, along with development of high-resolution CAD erosion composites (Green MS Thesis) • Training materials and case examples emphasizing the use of potential vorticity (PV) diagnosis in operational forecasting environments (Brennan, Lackmann, and Mahoney, 2006, Wea. Forecasting, conditionally accepted) For the 2 projects combined, the following represent dissemination of results to forecasters: • 16 Virtual Co-Lab or VISITVIEW presentations (featuring ~5-12 NWSFO each) • 7 Site visits by faculty and graduate students • 4 Workshops (one in Washington, DC and 3 in Raleigh, NC) • 7 Specialized training sessions (one at HPC, one in Boulder, and 5 in Raleigh) • 10 Conference preprints and presentations at major AMS conferences • 10 Peer-reviewed journal publications (3 in Mon. Wea. Rev., 7 in Wea. Forecasting) • 8 Student theses [Appel, Bailey, Stanton, Brennan (M.S.), Brennan (Ph.D.) Mahoney, Green, Haglund (partial support, expected 12/2006)] • The establishment of a collaborative research web site (http://www4.ncsu.edu/~nwsfo) • The establishment of the Mid-Atlantic CSTAR e-mail list • Creation of several posters and laminated reference materials, distributed regionally. Dr. Matt Parker, PI for “CAREER: Integrated Studies of Recurring, Non-Traditional Mesoscale Convective Systems”. Agency: NSF, May 2004 - April 2009, Amount $598,444 The results from this award are directly relevant to the proposed research on MCSs’ interactions with terrain. Accomplishments include: - Demonstration that the optimal state for long-lived squall lines suggested by Rotunno et al. (1988) is sensitive to the choice of numerical model, and to the diffusiveness and lower boundary condition of that model: published by Bryan et al. (2006) -

Discovery of downdraft CAPE and the ground-relative wind at the top of a convective system’s inflow layer as the most discriminatory parameters in forecasting severe convective winds; development of a new index that maximizes segregation of severe from non-severe convective environments: published by Kuchera and Parker (2006)

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Elucidation of a mechanism for backbuilding of convective systems, and explanation for the evolution and sensitivities of convective systems within realistic environments that include along–line vertical wind shear: published by Parker (2006a,b)

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Observational verification of the key processes in convective lines with leading stratiform precipitation (Parker and Johnson 2000), including the pre-line destabilization mechanism identified by Parker and Johnson (2004): published by Storm et al. (2006).

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PROJECT DESCRIPTION 1. Identification of research problems and approach a. Motivation and philosophy It is our view that weather forecasting can be improved in two fundamentally distinct ways: i) by improving the quality of Numerical Weather Prediction (NWP) model output, and ii) by improving the ability of operational forecasters to predict the weather using a variety of observational tools, conceptual models, and enhanced ability to interpret NWP output. Experience demonstrates that the two strategies are strongly linked. Improvement to NWP models may result from careful scrutiny of model output by astute operational forecasters, who examine model output on a daily basis and are most likely to identify problems. The second approach is required for the prediction of some weather phenomena, such as tornadoes, due to the inability of operational models to deterministically predict at such spatial scales. However, forecasters heavily utilize NWP output in order to anticipate the tornadic environment, and armed with an understanding of the dynamics of the problem at hand, they may correctly anticipate conditions conducive to such phenomena. Our philosophy in developing this proposal was to let operational forecasters identify the priorities, and then match these priorities with existing expertise on the faculty. Over a period of several months, we have worked with regional NWSFO to collect input concerning the topics for which they felt applied research would be most likely to benefit operations. Culminating in a regional CSTAR meeting on 2-3 August 2006, the response to our request for input has been met with an extensive list of scientifically oriented forecasting problems. The list of topics was too extensive, requiring us to narrow the focus to emphasize warm-season problems. By using the Mid-Atlantic CSTAR email distribution list, we were able to take part in a stimulating email dialog that allowed each office to voice their priorities. In working with the regional NWSFOs, we pointed out the need for scientifically defined (i.e., thesis-project compatible) research that would have high probability of useful operational impact when completed. We are confident that the primary research areas identified in this proposal (tropical cyclone impacts, eastern U.S. organized convection, and warm-season coldair damming) reflect a true consensus of NWS priorities for the 10 offices with whom we have communicated during this process. b. Technology transfer It is recognized that the project involves more than research, but cannot be deemed successful until the results of the research projects have been incorporated into the forecast process. As with previous CSTAR efforts, a variety of mechanisms will be employed towards this end, including the development of training materials, reference guides, AWIPS procedures, and collaborative case studies. We will work closely and directly with NWS staff to develop means for utilization of research findings in the NWS forecasting environment, including the gridded forecast database. c. Programmatic relevance and regional collaboration The research proposed herein is based on input from regional NWS offices, therefore the direct benefit to forecasters will be additional forecast tools during difficult forecast situations, and the ultimate benefit to the general public will be improved weather forecasts, particularly during the warm season (e.g., Fritsch and Carbone 2004). The proposal is relevant to the following long-term NWS priorities listed in the Request for Proposals (RFP): • Prediction of landfalling tropical cyclones, including associated precipitation and hazardous weather • The effect of topography and other surface forcing on local weather regimes • Locally hazardous weather, especially severe convection, and phenomena that affect aviation • Quantitative precipitation forecasting (QPF) • Application of sound science and innovative techniques toward optimizing the utilization of interactive forecast preparation systems and gridded databases. Additionally, the proposed research relates to the following NWS Eastern Region priorities:

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• Improved forecasts and warnings of severe weather and heavy precipitation during TC events. • Improved storm surge forecasts and coastal flood warnings during TC events. • Development of techniques to incorporate the effects of the region’s unique geomorphic features such as the Appalachian Mountains into operational forecast and warning services. • Development of improved, region-specific conceptual models for tornado, hail, and high wind (both convective and synoptic) events. Such development should include detailed investigation of the roles of mesoscale phenomenon such as thermal and moisture boundaries during these events. • Development of improved detection and warning techniques for low-topped severe convection and associated tornado development, and pulse convection events. The strong collaboration between NWSFO RAH and North Carolina State University (NCSU) fostered through previous projects (see “Results from Prior Agency Support” and http://www4.ncsu.edu/~nwsfo) was broadened to include the coastal and western Piedmont offices mentioned above during the previous CSTAR project. As demonstrated by the previous project, regional collaboration represents an efficient and wide-ranging benefit to university researchers, operational weather forecasters, and ultimately to the citizens of the region.

2. Proposed Work a. Tornadoes in landfalling tropical cyclones (Parker) i. Background and significance In recent years, a large number of significant hurricanes have made landfall in the United States. It is well known that many TCs spawn at least a few tornadoes after making landfall. Indeed, as TCs move inland and weaken, tornadoes become one of the greatest threats to society, and one of the most difficult forecast problems. It has been known for some time (e.g., McCaul 1987, 1991) that environmental wind profiles within onshore TCs possess very large storm-relative helicity (SRH); in turn, large SRH is known to be an ingredient for tornadoes in classical midlatitude thunderstorms (e.g. Rasmussen and Blanchard, 1998). Indeed, recent work by Davies (2006) suggests that the key discernable differences between tornadic and non-tornadic TCs are found in their lower-middle tropospheric vertical wind profiles. However, other studies (e.g., Curtis 2004) have suggested a correlation between the entrainment of dry air into tropical cyclones and their subsequent tornado production. This incursion of dry air is presumed to most strongly influence the potential buoyancy of air within the TC’s interior, both through increased solar surface heating, and through the generation of potential instability due to drying aloft. Finally, other recent studies have highlighted the importance of baroclinic surface boundaries in TC-tornado production (Edwards and Pietrycha 2006). Such boundaries involve horizontal gradients in both CAPE and vertical wind shear, so it is unclear which effect predominates, or whether the boundaries are important for another reason entirely. In short, the key operational ingredients for TC-tornadoes are still unclear, and the community currently lacks an understanding of the actual physical mechanisms whereby such ingredients, found on the scale of the hurricane itself (hundreds of km), arise and influence the production of tornadoes on the scale of an individual thunderstorm (~10 km). Much of the TC-tornado forecast challenge is due to the significant departures from the structures and environments of classic midlatitude tornadic thunderstorms: tornadic TC thunderstorms are almost certainly mini-supercells (e.g., McCaul and Weisman 1996), which are shallower, weaker, and less buoyant than Plains supercells but occur in high-wind, high-rotation environments with more vertical wind shear. As a result, midlatitude conceptual models have shown limited success when applied to TC tornadoes (McCaul 1991). Until recently, best operational practices were simply to issue tornado watches for the right-front quadrant, where tornadoes are most frequent (e.g. Novlan and Gray 1974; McCaul 1991). Tornadoes associated with TCs often develop rapidly, with signatures that last for only one or two radar volume scans (K. Keeter, personal communication, 2006). Therefore, nowcasters must be extremely alert in order to provide even short warning lead times to the public. The long-term goal of this application is to identify (from observations and numerical simulations) the principal differences between pre-

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landfall vs. post-landfall TCs, and between tornado-producing vs. non-tornado-producing TCs. As an outcome of the present application, the regional NWS offices will acquire improved situational awareness of key forecasting ingredients within potential TC-tornado environments. ii. Research objectives and plan of work In order to accomplish the goal of this application, the proposed study will pursue the following research objectives: Establish the key differences between prolific tornado-producing TCs and non-tornadoproducing TCs. This component of the study will involve 1) analysis of regional operational rawinsonde and gridded model analysis/reanalysis soundings and wind profiles from prolific vs. null TC cases; and, 2) analysis of quasi-operational simulations of prolific vs. null TC cases using the WRF model. The specific aims of this component are to document differences between the prolific and null cases that will be useful to forecasters, and to assess the ability of an operational model to represent and forecast these differences. Establish the operationally relevant post-landfall changes to the interior environment of prolific tornado-producing TCs, and the temporal and spatial scales on which the changes occur. This component of the study will involve 1) comparison of regional operational rawinsonde soundings with dropsondes from NOAA’s airborne missions near the time of landfall; and 2) analysis of quasioperational simulations of prolific TCs using the WRF model. The specific aims of this component are to document differences between the pre-landfall, post-landfall, and landfall +1 day environments within prolific TCs, and to assess the ability of an operational model to represent and forecast these differences. Demonstrate the sensitivities of a simulated TC’s interior mini-supercells to environmental features external to the TC. This component of the study will involve analysis of both quasioperational and quasi-idealized simulations of prolific TCs using the WRF model. The specific aims of this component are to assess the ability of an operational model to represent and forecast the minisupercellular mode of convection, and to test the influence of imposed dry air intrusions and baroclinic boundaries upon those forecasts/simulations. Working from the database of landfalling TCs that have influenced the county warning areas of our collaborating offices, and in direct collaboration with NWS forecasters, we will identify prolific tornado-producing TCs and null TCs over the southeastern U.S. from the past 10 years. We will perform surface analyses for each case and compare them to regional radar data and storm reports in order to determine which cells produced the tornadoes, and whether they occurred along baroclinic boundaries. We will composite and compare the values and vertical distributions of thermodynamic indices, lapse rates, vertical wind shear and relevant kinematic variables (e.g. storm-relative helicity). When landfall missions were flown by NOAA, we will also compare pre-landfall NOAA dropsondes to post-landfall rawinsonde observations. We will also acquire North American Regional Reanalysis (NARR) data for the identified cases and assess the gridded soundings. The NARR data have a vertical grid spacing of 25 hPa, horizontal grid spacing of 32 km, and are available in three hour intervals, which provide a reasonable representation of the coarse-scale evolution of the environments between standard sounding times. The NARR soundings will be compared with regional rawinsondes as a reality check, and their lower levels will be updated using actual surface observations for the best possible representation of surface-based CAPE, CIN, and vertical wind shear. If deemed unsuitable, gridded Rapid Update Cycle (RUC) analyses are also available. Owing to constraints on computer time and our desire to perform detailed analysis, it will not be possible to simulate all of the cases from the sounding assessment study. From our original sample of TCs, 3 or 4 of the most archetypal tornado-producers and nulls will be selected for numerical simulations with the WRF model in a quasi-operational configuration, using NARR data for initial and lateral boundary conditions. The goals of these simulations are to assess the model’s ability to provide lead time by capturing the key differences revealed in the sounding analysis, and to provide a

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proxy dataset with which we can perform high-resolution spatial analyses of variations in instability and vertical wind shear. We will work to understand both the differences between prolific vs. null cases, and the differences between the environments within pre-landfall vs. post-landfall TCs. Because (for this component) we wish to assess the ability of the model to forecast the evolution of the within-TC environment, we will first use grid spacings that are representative of current operational models (i.e. 12 km). We will then perform restart runs with nested domains using grid spacings of 1.25 km, which will permit development of supercell-like convective within the simulated TC bands. Finally, after assessing the representation of the convective storms in the 6-8 fine mesh WRF model simulations, we will then choose one null simulation in which to perform two sensitivity tests. First, we will artificially introduce dry air aloft, and then assess the changes to the simulated environment and subsequent changes to the convective storms within the simulated TC. And, second, we will artificially introduce lower tropospheric cooling in the vicinity of a TC rainband in order to slowly generate a baroclinic boundary, and again assess changes to the local environment and the convective storms within the nearby/intersecting rainband. During the completion of these research tasks, we will interact with all participating NWS offices, provide regular research updates, assist with efforts to develop operational tools that will aid operational forecasting in a real-time setting. Under the supervision of Dr. Parker, these TC-tornado objectives will be addressed by a graduate student researcher over the course of approximately two years.

b. MCS interactions with the Appalachian Mountains (Parker) i. Background and significance The diurnal precipitation Hovmöller diagrams of Carbone et al. (2002) showed that the signal of eastward–moving nocturnal convective systems over the central U.S. arrives at the Appalachian Mountains during the late afternoon of the following day. This phasing may lead to the reintensification of convection as the envelope of a precursor precipitation system approaches the eastern mountains. In some cases, such systems might even be able to cross the Appalachian chain and survive on the eastern side. Evans and Doswell (2001, their Fig. 3) found that a majority of the derechoes they studied ended on the western periphery of the Appalachian mountains, but documented a few cases that survived while traversing them (Fig. 1). In fact, their climatological corridor for “hybrid” derechoes passes over the tallest part of the Blue Ridge, from Kentucky and Tennessee into Virginia and North Carolina. Because Appalachian–crossing convective systems are a concern for operational forecasts in the eastern Piedmont, recent studies have begun to investigate the dynamics governing convective systems’ interactions with mountainous terrain. Frame and Markowski (2006) reviewed the scant literature on this topic and addressed the roles of peak height and spacing upon a mountain–crossing convective system. They suggested a replacement cycle in which the original convective line weakens while ascending the ridge’s windward slope, while the cold pool initiates a new convective line on the ridge’s lee side: after some of the outflow passes over the ridge, it descends the lee slopes rapidly within a supercritical flow regime, then undergoes a hydraulic jump and resumes deep lifting. In this regard, the time of day may again be important: the decreased low–level stability of the afternoon would hinder the cold pool less as it ascended the windward slope.

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Figure 1. Radar mosaic of an MCS crossing the Appalachian Mountains (a-c), and corresponding Storm Prediction Center (SPC) severe weather reports.

Parker and Ahijevych (2006) studied nine years’ worth of radar data from the east-central U.S. and found that a large fraction of the eastward moving convective episodes that developed west of the Appalachians ended before they crossed the Appalachians, with a maximum in dissipation on the western slope of the Blue Ridge (81–82°W). In fact, only 10% of the episodes that began west of the Cumberland Plateau survived to the eastern side of the Blue Ridge. A much larger fraction of the episodes that began over the Cumberland Plateau survived all the way across the Blue Ridge, and almost all of those that began over the Blue Ridge survived to its east. Although episodes dissipated much more frequently than they crossed the Appalachians, during the study period 127 systems (14/year) starting west of the Blue Ridge were able to complete the journey (e.g., Fig. 2). These successful crossings were most likely when episodes approached the Appalachians around the time of the local diurnal maximum (i.e. the window from 1700-2200 UTC). Such phasing is not uncommon, and is loosely depicted in the long–term averaged Hovmöller diagrams of Carbone et al. (2002). Much as suggested by the replacement cycle of Frame and Markowski (2006), within our nine year dataset there were indeed occasions when convective systems dissipated on the western slope of the Appalachians, but then reformed on the eastern slope. Frame and Markowski (2006) noted that increasingly tall ridges more strongly favor the disruption and replacement cycle associated with the cold pool’s passing over a ridge. Although they considered mountains as tall as 1800 m in their idealized framework, it still may be that the Blue Ridge is too tall for some cold pools to cross over. In this regard, the Froude number of the outflow is also important (Reeves and Lin 2005), and this in turn may be a function of the thermodynamic environment. Yet another intriguing possibility is that the potential vorticity (PV) anomalies generated by mesoscale regions of convective and stratiform heating may be advected over the terrain in the middle troposphere even when a system’s cold pool is largely blocked. Once on the lee side, if CAPE is present, the PV anomalies could then aid in redevelopment through processes such as described by Raymond and Jiang (1990) and Fritsch et al. (1994). Prior studies using irrotational 2D or quasi–2D model configurations would be unable to capture such an effect, so additional study is warranted.

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Figure 2. Radar mosaic Hovmöller diagram for an MCS that crossed the Blue Ridge Mountain region during 17–18 June 2000.

ii. Plan of work A radar climatology of Blue Ridge-crossing MCSs has largely been completed by members of the CSTAR collaboration, including the nine-year statistical analysis of radar data by Parker and Ahijevych (2006) and the results emerging from a study of trends in severe weather reports associated with MCSs that approach the Appalachians from the west (S. Keighton and J. Jackson of NWSBlacksburg; J. Guyer and J. Peters of SPC; currently unpublished). Given this solid observational background, the next logical step is a process study using the WRF model. In order to accomplish the goal of this application, the proposed study will pursue the following research objectives: Establish the key physical differences between mountain-crossers and non-crossers in realistic operational scenarios. This component of the study will involve quasi-operational numerical weather simulations with the WRF model. The specific aims of this component are to understand the relative roles of the MCSs’ outflows and PV anomalies as well as terrain-linked gravity waves and solenoidal circulations. Establish the sensitivity of mountain-crossers to key environmental and terrain parameters. This component of the study will involve controlled sensitivity experiments using idealized numerical simulations. The specific aims of this component are to understand the roles of the local thermodynamic sounding and wind profile, the length and orientation of an MCS’s convective line relative to the ridge it is approaching, and the time of day at which the line approaches the ridge. Working from the database of cases identified by Parker and Ahijevych (2006) and our NOAA collaborators, we will identify 3 or 4 archetypal Blue Ridge crossers and 3-4 archetypal dissipating MCS cases for simulation with the WRF model in a quasi-operational configuration, using NARR data for initial and boundary conditions. In order to maintain computational tractability but properly depict the convective systems, the finest mesh will have a grid spacing of 1.25 km. The goals of these simulations are to assess the model’s ability to provide lead time by capturing the key differences between crossers and non-crossers, and to provide a proxy dataset with which we can perform highresolution spatial analyses of outflow behavior, generation and advection of middle tropospheric PV

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anomalies, and interactions between simulated convective systems and terrain-linked gravity waves and solenoidal circulations. After assessing the representation of the convective storms in the 6-8 fine mesh WRF model simulations, one crosser and one non-crosser simulation will be selected, with which to perform idealized sensitivity tests on the fine mesh. We will use homogeneous initial conditions and artificially initiate the upstream MCS within the model, but will include realistic (Blue Ridge-like) terrain whose orientation1 we can modify. Unlike the simulations of Frame and Markowski (2006), our idealized simulations will not use a periodic along-ridge boundary condition. A fully 3D domain is necessary in order to assess the role of the cold pool’s finite extent, and in order for an MCS to produce realistically shaped PV anomalies. We will then perform sensitivity experiments in which we increase the stability of the homogeneous environment, modify the terrain orientation, modify the initial size of the convective system, and permit diurnal variations to occur both in phase and out of phase with the MCS’s approach. During the completion of these research tasks, we will interact with all participating NWS offices, provide regular research updates, assist with efforts to develop operational tools that will facilitate forecaster ability to differentiate between crossers and non-crossers in a real-time setting. Under the supervision of Dr. Parker, these MCS-interaction objectives will be addressed by a graduate student over the course of approximately two years.

c. Warm-season cold-air damming & wedge-front convection (Lackmann) i.) Background Forecasting challenges associated with warm season CAD share some similarity to their cold season counterpart in that prediction of the location and character of the CAD airmass boundary, and timing of CAD erosion, remain problematic. An additional problem that characterizes warm-season CAD is the occurrence of convection near the periphery of the CAD cold-dome, along the so-called “wedge front”. This problem is not limited to the warm season, as evident from the 2-3 January 2006 example highlighted by the Peachtree City NWS office during the regional August 2006 CSTAR workshop. Previous CAD research has emphasized the spectrum of event types, and has highlighted what had been one of the most challenging aspects of CAD forecasting, CAD erosion (e.g., Bailey et al. 2003; Stanton 2004; Lackmann and Stanton 2004). However, the focus of the majority of CAD studies has been for cold-season events, and as the Bailey et al. (2003) climatology revealed, a significant number of CAD events take place during the warm season. If weak CAD events are included, a 10-year climatology revealed that August and September have the highest frequency of CAD events (Bailey et al. 2003, their Fig. 5). These weak CAD events thus peak during hurricane season; in section e of this proposal, the related problem of CAD boundary influence on TC QPF will be discussed. There is a clear need to examine the warm season CAD problem. Our efforts will therefore focus upon: • Problems relating to prediction of convection at the periphery of the cold dome, and • Prediction of the location of the wedge front during the evolution of warm-season CAD events, which is tied to the problem of warm-season CAD erosion. Although the problem of CAD erosion is present regardless of season, many of the forecasting challenges associated with warm-season CAD are distinct from those accompanying cold-season events. For example, in terms of QPF, cold-season CAD is often characterized by overrunning (warm advection), with strong ascent forced even over the interior of the cold dome and abundant precipitation falling into the cold dome. In contrast, warm-season CAD events are often characterized by upright convection in the convergent frontal zone at the periphery of the CAD event, with the more stable interior of the damming region devoid of precipitation, with the result being a “ring of fire” precipitation pattern (Fig. 3a).

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Frame and Markowski (2006) have nicely shown the sensitivity of MCSs to the terrain height.

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Figure 3. (a.) Surface observations and 2-km composite radar mosaic valid 20 UTC 30 July 2003, and (b) Eta model 18-h sea level pressure and 6-h quantitative precipitation forecast valid 00 UTC 31 July 2003.

The then-operational Eta model had difficulties with QPF for this July 2003 event (Fig. 3b); the model forecast indicated a maximum of precipitation over north-central NC and south-central VA, when in fact convective precipitation was observed instead around the periphery of the cool dome, over SC and the coastal plain of NC. The radar precipitation pattern is nearly the opposite of the model QPF for this event, despite the fact that this is a relatively short-range (18 hour) forecast. In this example, the Eta failure appeared to be due in part to premature erosion of the CAD air mass, and overly aggressive northward retreat of the CAD boundary (and forcing for ascent). Aside from QPF, another important facet of warm-season CAD forecasting is the occurrence and/or character of convection at the periphery of the cold dome. Severe storms may form in the convergent, sheared environment found near the edge of the cold dome, and the Peachtree City, Columbia, and Charleston SC offices have all cited this phenomenon as a critical forecasting concern. A better understanding of the character of the boundary layer on both sides of the wedge front (warm- and cool-season) is critical, as is understanding how convection will be altered by the presence of the CAD boundary. The primary objectives for this component of the project are: • To determine the synoptic settings that dictate the location (southward extent) and intensity of the wedge front for warm-season events, • To elucidate the differences between warm- and cool-season CAD erosion mechanisms and investigate model representation of these processes during the warm season, • To distinguish the synoptic- and mesoscale environments for CAD events with and without severe peripheral convection, and • For convectively active events, to better understand the affect of the wedge front on shear and instability characteristics in their immediate vicinity. The convective forecasting issues related to CAD as discussed in the previous section are also clearly related to the location of the CAD airmass boundary, or wedge front. Predicting the location of the wedge front is thus to some extent linked to prediction of CAD erosion, especially for forecasts during the mature stages of an event. If the location of the wedge front can be accurately forecasted (i.e., how far to the south the cold dome will extend), then the other related forecast challenges would be easier to handle. Convection aside, cloud cover and temperatures are always a forecasting concern, and the wedge front’s location in the summer can sometimes mean the difference between a high in the 70s and a high in the 90s. ii.) Objectives and methodology Objective 1: Determine factors most useful for determining the character and location of the wedge front. Specifically, we seek to define the synoptic conditions that allow the wedge front to extend beyond the southern edge of the Appalachians and into western Georgia as opposed to remaining in the Carolinas or Virginia. We must also differentiate wedge-front conditions that are

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characterized by active, severe convection from those events which are inactive, and between CAD events characterized by strong versus weak wedge fronts. Methods: Now that higher resolution Rapid Update Cycle (RUC) and NARR datasets are available (e.g., Green 2005), we can construct composites using an existing database of CAD events from Bailey et al. (2003) or Green (2005) but with a specific emphasis on warm-season events. Composites will be generated specifically for warm season events with larger or smaller south and westward extent, with some basic parameters such as the strength of the along-barrier pressure gradient and the stability of the CAD airmass explored as possible forecast parameters. Additionally, composites will be generated for cases with high and low shear environments along the wedge front, and for strong versus weaker temperature gradients. We expect these latter two samples to be consistent, via thermal wind arguments. Examination of previous warm-season cases during earlier CSTAR efforts revealed the importance of “solar sheltering” by stratus or stratocumulus clouds to maintenance of the CAD airmass. Several online satellite data sources (e.g., the NESDIS GOES archive, which spans the years of previous CAD climatologies: see http://www.ncdc.noaa.gov/oa/rsad/gibbs/gibbs.html) will allow for an observational characterization of the extent of cloud cover during warm season CAD events, and this can be related to the persistence of the event. Composites stratified by degree of cloud cover are expected to provide operationally relevant guidance to help distinguish strong and weak wedge front examples. We hypothesize that cases characterized by extensive cloud cover will preserve a stronger thermal gradient, and thus be more likely to exhibit strong vertical wind shear and perhaps severe convection on the periphery. Objective 2: Improve understanding and prediction of warm-season CAD erosion. Intense summertime solar radiation and observations of previous warm-season CAD events suggests that there is a diurnal signal to CAD advance and erosion. This has not been investigated to our knowledge, and there are important forecast implications. Furthermore, cloud-radiation interactions in forecast models, along with the ability of models to represent the CAD inversion layer and shallow stratus and stratocumulus, are critical aspects that must be understood. The dominant mechanisms that characterize warm-season CAD may differ markedly from those during the cold season. For example, during the cold season, cold advection aloft was found to be one of the most effective mechanisms to weaken the CAD inversion and initiate the breakdown of a CAD event. However, with much more intense solar radiation in the warm season, solar heating of the cold dome is likely to play a much larger role relative to that in the cold season, and thus “solar sheltering” (the maintenance of the near-surface cold layer by the cooling influence of cloud cover) becomes critical. Owing to the dearth of warm-season CAD research, forecasters may be tempted to apply cold-season research results to warm-season events. A systematic study of warm-season CAD results would allow a more thorough examination of the dynamics and forecasting issues associated with these events. Methods: Case studies will be developed that will draw on our prior knowledge of the factors influencing CAD evolution. For instance, the activity of the shallow mixing scheme (Lackmann and Stanton 2004) in the Betts-Miller-Janjic (BMJ) convective scheme will be investigated in order to determine if this remains problematic for warm season cases. By running WRF with different convective scheme options, such as the Kain-Fritsch and altered version of the BMJ (with shallow mixing disabled), we can pinpoint the importance of this aspect for warm season CAD erosion. This would be helpful in addressing the problem of premature CAD erosion in model forecasts, and would serve to guide local modeling efforts. Specifications for horizontal and vertical grid spacing, sensitivity to cloud microphysical parameterization, and model radiation schemes will also be investigated in collaboration with Dr. Brad Ferrier and others at NCEP, and will draw upon experience from previous research by Lackmann and Stanton.

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Objective 3: Improve understanding of the character of the lower troposphere in the vicinity of the wedge front during events with peripheral convection. As mentioned above, we hypothesize a linkage between the strength of the thermal gradient at the wedge front and the vertical shear at the periphery of the cold dome, via the thermal wind relation. Thus, provided that instability can be accurately forecast, the accurate prediction of severe wedge front convection may be tied to accurate prediction of the CAD event itself. In the warm season, abundant moisture and instability are typically found surrounding the CAD air mass, and the convergent flow near the wedge front provides a lifting mechanism. Thus the strength of wedge-front shear is perhaps the most critical forecasting parameter. Methods: This aspect will also rely on a series of observational and modeling case studies, with the goals of documenting the convective environment in the vicinity of the wedge front. Thermal wind computations will be used to determine if the horizontal temperature gradient is sufficient to appreciably affect the vertical wind shear, and if so, where the zone of enhanced shear lies relative to areas of greatest instability. Model experiments in which the topography is removed prior to the setup of the CAD event will allow determination of the specific role of CAD in determining vertical wind shear, convergence, and instability during events featuring wedge-front convection.

d.) Coastal flooding problem (Xie) i.) Background Storm surge modeling at North Carolina State University (NCSU) began in the late 1970’s. The NWS Forecast Office at Raleigh began collaboration with NCSU in the late 1980’s focused upon coastal flooding associated with mid latitude storms. The utility of the NCSU surge model (developed by Xie) with respect to tropical cyclones was explored as well. By the time Hurricane Emily struck the Outer Banks of North Carolina on 31 August 1993, surge modeling at NCSU was becoming more robust. Indeed, the model correctly predicted record-breaking sound side flooding of 10-11 feet at Hatteras Island on the backside of Hurricane Emily. The success associated with this event and the others that followed resulted in the nearly routine production of storm surge scenarios associated with tropical cyclones that threaten North Carolina during the late 1990’s to the present time. The move of the NWS Forecast Office at Raleigh (1994) to the NCSU campus, collocated with the Department of Marine, Earth, and Atmospheric Science, made for more effective and efficient collaborations. The collaboration was extended to include NWS personnel from coastal forecast offices during the late 1990s to present time. The NWS – NCSU collaboration on storm surge modeling has enjoyed a long history. While the basic physics and processes of storm surge are well understood by the scientific community, the interactions between storm surge, waves, tides and inland flooding and the resulting coastal flooding still present a major challenge. The collaboration’s next logical step is to investigate the complex interactions between the hydrological processes in the coastal region where river, estuary and coastal waters meet. ii.) Hypothesis Our fundamental hypothesis is that an integrated research and training program on storm surge and coastal flooding modeling and forecasting will improve our understanding of the coastal flooding problem in regions where estuarine, lagoonal and coastal waters interact, which will, in turn, lead to improved operational coastal flooding forecasts. We also hypothesize that the characteristics and nature of coastal flooding problems are different in different forecast regions, thus it is important to consider local meteorological, hydro-geological and oceanographic conditions in storm surge and coastal flooding modeling and forecasting. For example, a hurricane wind field will more likely be asymmetric due to interactions with mid-latitude troughs at regions of higher latitudes than that at lower latitudes, whereas in sounds and estuaries, the effect of fresh water runoff will be a more important issue than at open coastal regions. The “sloshing effect” is another important and unique problem in bays and estuaries. The effect of tides is also region-dependent. In semi-enclosed shallow estuaries such as the Pamlico Sound, tidal effects are small, so the tides can be ignored during the

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computation of storm surge. On the other hand, in some coastal areas, tides can be a substantial portion of water level variation, and hence coupled surge and tide computation is more appropriate. iii.) Proposed Work Despite the fact that storm surge is a well-known coastal phenomenon and can often be well simulated in hindcasts, accurate operational storm surge and inundation forecasting is still a challenge, particularly in regions where river, estuaries, and coastal waters meet. In this study, we propose to address the following scientific and technical issues related to operational storm surge and inundation forecasting. Task 1: Sensitivity of storm surge to hurricane wind asymmetry: Current operational storm surge forecasting models rely on parametric hurricane wind models (such as the Holland model and SLOSH wind model) to compute wind forcing using minimum pressure and radius of maximum wind (Xie et al., 2006a). An important scientific issue is the sensitivity of storm surge to various types of parametric hurricane wind models. How does the asymmetry of hurricane wind distribution affect the surge? How does the size of a hurricane affect the surge? Do parametric hurricane wind models work better off the coast of South Florida than off the coast of North Carolina and Virginia? Do parametric hurricane wind models work better over open water than over inland waters, such as sounds, bay areas and lakes? Do mesoscale weather forecast models such as WRF provide a better choice for forecasting storm surface winds? These questions will be addressed through a series of sensitivity experiments using the NCSU storm surge model (Xie et al., 2004) using the standard symmetric hurricane wind model (Holland, 1980) as well as asymmetric wind model (Xie et al., 2006a). Task 2: Sensitivity of storm surge and coastal inundation to drag coefficient at high wind speed: A significant error in storm surge forecasting can be attributed to the lack of knowledge of drag coefficient at high wind speeds. Recent observations indicate that drag coefficient decreases with wind at high wind speeds (Powell et al., 2006). What is the impact of the computation of wind stress at high wind speed on storm surge forecasts? We will carry out a series of model runs with a well-designed set of numerical experiments considering different drag coefficient formulations at high winds based on the observed change of drag coefficient as a function of wind speed as shown in Powell et al. (2006). Task 3: Coupled coastal flooding: Surge, tides and waves often interact, but current operational surge forecast models are handling them separately. Do surge-tide-wave coupled modeling systems provide a better alternative to storm surge forecasting? We will use the surge-wave-coupled model developed at NCSU to study the effect of wave and tide on storm surge and coastal inundation using coupled as well as stand-alone experiments. Task 4: Coastal flooding in estuaries and sounds: In estuarine and sounds, fresh water flooding plays a significant role in the overall coastal and inland flooding. How sensitive is storm surge and inundation to the fresh water input from rivers? Historical cases, including Hurricane Floyd and Hurricane Katrina will be used as case studies to examine the benefit of coupling inland flooding to storm surge forecasting. Task 5: Negative surge: Present operational storm surge flooding does not provide information about negative surge, which is a reduction in sea level when strong offshore winds develop near a TC. While negative

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surge does not pose a threat to life and property directly, drying in coastal areas can cause catastrophic damage to the ecosystem. How do we improve the handling of negative surge in numerical surge models? We will analyze the dynamics of negative surge using the surge equation and analytical approach as well as computational modeling approach using the NCSU storm surge model. Preliminary results on this topic are reported in Peng et al. (2006).

e. TC QPF, boundary interactions, and modeling (Xie and Lackmann) i.) Background Flooding is one of the most hazardous weather conditions in terms of casualties and property damage each year in the United States. For example, in 2003, there were 438 weather-related fatalities and 2924 injuries with a total property/crop damage of $11.4 billion, among which flooding caused 86 fatalities, 70 injuries and about $2.7 billion in property/crop damage. Therefore, improving Quantitative Precipitation Forecasting (QPF) and estimation (QPE) and hence better flood forecasting is important for preventing the loss of lives and property. QPF has been a major challenge in weather forecasting and its improvement is very slow compared to other quantities such as temperature and wind fields. The difficulties come from the uncertainties of both initial conditions and physical parameterization (or model errors). Therefore, improving the initial conditions is one way to improve QPFs. On the other hand, with the development of remote sensing technology, more and more observational data are available from radar and satellite, which provides a large resource for improving the initial conditions. So, making optimal use of these observations to improve the initial condition of NWP models is critically important. Four-dimensional variational data assimilation (4DVAR), developed from mathematical control theory, is one of the most advanced and effective assimilation approaches. It solves for the best initial conditions for weather forecasting by minimizing the short-range forecast error. It has a great advantage over the traditional methods, i.e., it can directly assimilate different types of observations distributed over space and time while maintaining the dynamical and physical consistency with the governing equations. Furthermore, 4DVAR maybe the one of most appropriate approaches for precipitation assimilation, considering the precipitation feature of small scale in space and rapid change in time. As evident from the dialog with our NWS collaborators, precipitation accompanying landfalling cyclones presents a major high-impact forecast challenge. Previous studies have examined the factors that contribute to left-of-track or right-of-track precipitation (e.g., Srock et al. 2005) and other factors that can influence the amount and distribution of precipitation accompanying a landfalling TC (e.g., Bosart and Lackmann 1995; Atallah and Bosart 2003; Colle 2003; Cline 2003; Croke 2005). Factors found to influence TC precipitation include interaction with pre-existing upper troughs and jets, as well as interaction with low-level boundaries and warm-season CAD. Surprisingly, Croke (2005) found no strong correlation between initial storm strength and translation speed and heavy inland precipitation, instead emphasizing the dynamical effects of upper trough and lower boundary interactions. While these results differ from the findings of Konrad et al. (2002), they nevertheless underscore the importance of dynamical factors in precipitation focusing and production during landfalling TC events. The QPF problem is also, for the western portion of the Southeast and MidAtlantic CSTAR region, linked to topographic lift. Recent examples of landfalling TCs that interacted with lower-tropospheric boundaries to produce strong spatial gradients of precipitation include Tropical Storm Alberto (2006), Tropical Storm Kyle (2002), and Hurricane Floyd (1999). Alberto inundated parts of central North Carolina with over 7” (175 mm) of rain and produced flash flooding as the weakening TC interacted with a thermal boundary oriented SW-NE across the state. Kyle moved northwest into a well-defined CAD event, while the focus of precipitation in Floyd was shown to have been influenced by interaction with a deep baroclinic zone in addition to a CAD-like boundary and coastal front (Atallah and Bosart 2003; Colle 2003).

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These boundaries are not only important as precipitation focusing mechanisms, but also hold important implications for the occurrence of tropical storm or hurricane-force winds at the surface. The stable air on the cold side of the boundary may inhibit mixing, leading to relatively weak surface winds compared to locations on the warm side of the boundary, where momentum mixing would be more effective. Hurricane Isabel (2003) represents an example of an event in which a weak lowertropospheric boundary evidently exerted a strong influence on the location of damaging winds. For additional discussion of this hypothesis, see http://www4.ncsu.edu/~nwsfo/storage/cases/20030918/. Clearly, it would be useful to better predict the occurrence, location and intensity of these boundaries, as well as to identify the critical parameters that dictate mixing and surface wind speed. A question with important predictability implications thus arises: To what extent are these boundaries, and the cool air mass often found north and west of the boundary, attributable to the landfalling TC itself? The answer to this question has important predictability implications, because the representation of TCs in operational models remains problematic, in the GFS due to limited resolution, and in the NAM due to challenges in the data assimilation process. Physical processes that are hypothesized to link these boundaries to the TC include (i) diabatic CAD effects due to cloud cover and evaporational cooling on the cool side of the boundary, and (ii) enhanced southward ageostrophic flow on the cool side of the boundary due to the presence of the right entrance of the upper outflow jet as well as surface pressure falls associated with the TC itself. If the boundaries are indeed shown to be linked to the TC, then the forecast process should be modified so as to emphasize observational analysis and reduce reliance on model output fields. Alternatively, local modeling efforts could be designed to specifically address the issue of lower boundary formation. ii.) Method: Presence or absence of boundaries: A sufficiently large TC sample exists to enable generation of composites of landfalling TCs that are characterized by pronounced, moderate, or weak lower boundaries over the southeastern U.S. Composites of conditions prior to landfall will be derived for each sample, thereby enabling forecasters to better anticipate the likely occurrence of boundaries. The presence or absence of signals such as upstream dew point depression, high pressure to the north, and confluence in the near-surface wind field will be linked to the physical frontogenesis process using these case samples. Selected case studies will be undertaken (described in the next subsection) to further elucidate these linkages. The implied surface wind and precipitation distributions will also be derived from these composites, which will be based on either RUC or NARR gridded datasets. Boundary formation, intensity, and location: We will build on earlier work by undertaking careful WRF modeling studies of 2 or 3 TC events in which lower boundaries were observed. Experiments with the initial TC vortex removed will be compared to “full IC” runs, and runs with an enhanced initial TC, to better ascertain the role of the TC and its outflow in determining the location and intensity of lower boundaries. PV inversion techniques, such as that employed by Henderson and Lackmann (1999) and Brennan and Lackmann (2005) will be used to alternatively remove or enhance the initial TC strength. An improved understanding of the relative dependence of lower boundaries on initial TC representation will be useful for operational prediction. Vertical momentum transport: In order to examine the role of enhanced stability in the lower troposphere west of boundaries, we will study examples such as Isabel (2003) using numerical experiments with the WRF model. For example, in the case of Isabel, a shallow dry layer was present to the north of the landfall location prior to landfall, and evaporational cooling evidently enhanced stability as precipitation from the storm overspread the region. Experiments in which the pre-storm humidity is increased prior to the arrival of precipitation (maintaining the initial lapse rate) will be performed in order to examine the impact on surface winds in a storm-relative sense. Cases such as Isabel could be used for this experiment, and analysis of vertical momentum transport, boundary layer stability, and surface wind speed would be investigated for the two main boundary layer scheme options in WRF-ARW, the Yonsei University and Mellor-Yamada-Janjic schemes.

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Initial condition improvement: We will explore the use of 4DVAR to assimilate satellite, radar, and gauge-based QPE data sets, in order to determine the ability of these data to improve QPFs and thus forecasts of flooding by the coupled watershed-estuary modeling system. The data assimilation study will use the WRF model, as well as its adjoint models. For verification, two experiments will be conducted: one serving as a control run without data assimilation, and another using 4DVAR to assimilate observational data into the model. This activity will be limited to a “proof of concept” level due to resource limitations, but will be explored to pave the way for future opportunities. 3. Facilities, human resources, and deliverables Facilities available in support of this research include many networked UNIX workstations at NCSU, and two Linux computing clusters that will be used for running models and data analysis. The Unidata Local Data Manager (LDM) software, running on a central server at NCSU in Jordan Hall, will be a source of observational and model data for our studies. The start date of 1 May 2007 would be ideal for the recruiting of graduate research assistants to the project, given that funding decisions are expected prior to the end of the spring recruiting period. We anticipate that 4 M.S. students will work on this project, with overlap during year 2. A strength of past CSTAR efforts has been that many participating students have gone on to pursue careers in the NWS. Accordingly, efforts will be made to recruit graduate students who hold such an interest. As a part of these research efforts, direct collaboration and periodic updates, VISITVIEW sessions, workshops, and seminars will be scheduled as results warrant in order to ensure a true collaboration and direct interaction between the PIs, graduate students, and NWS personnel. References Atallah, E. H. and L. F. Bosart 2003: The extratropical transition and precipitation distribution of Hurricane Floyd (1999). Mon. Wea. Rev., 131, 1063–1081. Bosart, L. F., and G. M. Lackmann, 1995: Postlandfall Tropical Cyclone Reintensification in a Weakly Baroclinic Environment: A Case Study of Hurricane David (September 1979). Mon. Wea. Rev. 123, 3268–3291 Bailey, C. M., G. Hartfield, G. M. Lackmann, K. Keeter, and S. Sharp, 2003: An objective climatology, classification scheme, and assessment of sensible weather impacts for Appalachian cold-air damming. Wea. Forecasting, 18, . Brennan, M. J., and G. M. Lackmann, 2005: The influence of incipient latent heat release on the precipitation distribution of the 24–25 January 2000 U.S. East Coast cyclone. Mon. Wea. Rev., 1913–1937. Bryan, G.H., J.C. Knievel, and M.D. Parker, 2006: A multi-model assessment of RKW Theory's relevance to squall line characteristics. Mon. Wea. Rev., 134, 2772–2792. Carbone, R. E., J. D. Tuttle, D. A. Ahijevych, and S. B. Trier, 2002: Inferences of predictability associated with warm season precipitation episodes. J. Atmos. Sci., 59, 2033–2056. Cline, J. W., 2003: Recent tropical cyclones affecting North Carolina. M.S. thesis, University of Miami, 43-47 pp. Colle, B. A., 2003: Numerical simulations of the extratropical transition of Floyd (1999): Structural evolution and responsible mechanisms for the heavy rainfall over the Northeast United States. Mon. Wea. Rev., 131, 2905–2926. Croke 2005 Examining Planetary, Synoptic and Mesoscale Features that Enhance Precipitation Associated with Landfalling Tropical Cyclones in North Carolina. Curtis, L., 2004: Midlevel dry intrusions as a factor in tornado outbreaks associated with landfalling tropical cyclones from the Atlantic and Gulf of Mexico. Weather and Forecasting, 19, 411–427. Davies, J.M., 2006: Hurricane and tropical cyclone tornado environments from RUC proximity soundings. 23rd Conference on Severe Local Storms, 6-10 November 2006, St. Louis, MO. CDROM P8.1.

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Edwards, R. and A. E. Pietrycha, 2006: Archetypes for surface baroclinic boundaries influencing tropical cyclone tornado occurrence. 23rd Conference on Severe Local Storms, 6-10 November 2006, St. Louis, MO. CD-ROM P8.2. Evans, J. S., and C. A. Doswell, III, 2001: Examination of derecho environments using proximity soundings. Wea. Forecasting, 16, 329–342. Frame, J., and P. Markowski, 2006: The interaction of simulated squall lines with idealized mountain ridges. Mon. Wea. Rev., 134, 1919–1941. Fritsch, J. M., J. D. Murphy, and J. S. Kain, 1994: Warm-core vortex amplification over land. J. Atmos. Sci., 51, 1780–1807. Fritsch, J. M. and R. E. Carbone, 2004: Improving Quantitative Precipitation Forecasts in the Warm Season: A USWRP Research and Development Strategy, Bull. Amer. Meteor. Soc. 85, 955-965. Henderson, J., G. M. Lackmann, and J. R. Gyakum 1998: An application of potential vorticity inversion to the movement of Hurricane Opal. Mon. Wea. Rev., 127, 292−307. Keeter, K. K., S. Businger, L. G. Lee, and J. S. Waldstreicher, 1995: Winter weather forecasting throughout the Eastern United States. Part III: The effects of topography and the variability of winter weather in the Carolinas and Virginia. Wea. Forecasting, 10, 42–60. Konrad C. E. II., M. F. Meaux, and D. A. Meaux, 2002: Relationships between tropical cyclone attributes and precipitation totals: considerations of scale. Int. J. Climatol., 22, 237–247. Srock, A. F. L. F. Bosart, J. Molinari, 2005: Composite and case studies of precipitation distribution in U.S. landfalling tropical cyclones. NHC Conference Preprints 16C.6. Kuchera, E.L., and M.D. Parker, 2006: Severe convective wind environments. Wea. Forecasting, 21, 595–612. Mahoney, K. M., 2005: The effect of upstream convection on downstream precipitation. M.S. thesis, Dept. of Marine, Earth, and Atmospheric Sciences, North Carolina State University, 204pp. Mahoney, K. M., and G. M. Lackmann, 2006a: The effects of organized upstream convection on downstream precipitation. In Press, Wea Forecasting. 21. Mahoney, K. M., and G. M. Lackmann, 2006b: The Sensitivity of Numerical Forecasts to Convective Parameterization: A Case Study of the 17 February 2004 East Coast Cyclone. Wea. Forecasting. 21, 465–488. McCaul, E.W., Jr., 1987: Observations of the Hurricane “Danny” tornado outbreak of 16 August 1985. Monthly Weather Review, 115, 1206–1223. McCaul, E.W., Jr., 1991: Buoyancy and shear characteristics of hurricane-tornado environments. Monthly Weather Review, 119, 1954–1978. McCaul, E.W., Jr. and M.L. Weisman, 1996: Simulations of shallow supercell storms in landfalling hurricane enviornments. Monthly Weather Review, 124, 408–429. Novlan, D.J., and W.M. Gray, 1974: Hurricane-spawned tornadoes. Mon. Wea. Rev., 102, 476–488. Parker, M.D., 2006: Simulated convective lines with parallel stratiform precipitation. II: Governing dynamics and associated sensitivities. J. Atmos. Sci., in press. Parker, M.D., and D.A. Ahijevych, 2006: Convective episodes in the east—central United States. Mon. Wea. Rev., submitted. Parker, M. D., and R. H. Johnson, 2000: Organizational modes of midlatitude mesoscale convective systems. Mon. Wea. Rev., 128, 3413–3436. Parker, M.D., and R.H. Johnson, 2004: Simulated convective lines with leading precipitation. Part II: Evolution and maintenance. J. Atmos. Sci., 61, 1656–1673. Powell, M. D., P. J. Vickery, and T. A. Reinhold, 2003: Reduced drag coefficient for high wind speeds in tropical cyclones. Nature vol 422, March 20 pp.279–283 Rasmussen, E.N., and D. O. Blanchard, 1998: A baseline climatology of sounding-derived supercell and tornado forecast parameters. Wea. Forecasting., 13, 1148–1164. Raymond, D. J., and H. Jiang, 1990: A theory for long–lived mesoscale convective systems. J. Atmos. Sci., 47, 3067–3077. Reeves, H.D., and Y.-L. Lin, 2005: The effects of orography on the propagation and precipitation distribution of pre-existing mesoscale convective systems under different Froude number flow regimes. 11th Conference on Mesoscale Processes, 24-28 October 2005, Albuquerque, NM. CDROM 3M.1A.

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Storm, B.A., M.D. Parker, and D.P. Jorgensen, 2006: A convective line with leading stratiform precipitation from BAMEX. Mon. Wea. Rev. in press. Xie, L., S. Bao, L. J. Pietrafesa, K. Foley and M. Fuentes, 2006a: A Real-Time Hurricane Surface Wind Forecasting Model: Formulation and Verification. Monthly Weather Review, 134, 1355– 1370. Xie, L., H. Liu, L. J. Pietrafesa, M. Peng, 2006b: The effect of wave-current interactions on the storm surge and inundation in Charleston Harbor during Hurricane Hugo 1989. J. Geophysical Research (in review). Xie, L., L. J. Pietrafesa, and M. Peng, 2004: Incorporation of a mass-conserving inundation scheme into a three-dimensional storm surge model. J. Coastal Research, 20, 1209–1223.

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Gary M. Lackmann EDUCATION Ph.D., Atmospheric Science, University at Albany, State University of New York, May 1995 M.S., Atmospheric Science, University of Washington, March 1989 B.S., Atmospheric Science, University of Washington, June 1986 PROFESSIONAL EXPERIENCE Assistant Professor, North Carolina State University. August 1999 to present Assistant Professor, State University of New York, College at Brockport. September 1996 to August 1999 Postdoctoral Research Scientist, McGill University. July 1995 to August 1996 Physical Scientist, Naval Postgraduate School. February 1989 to September 1989 Physical Scientist, NOAA/Pacific Marine Environmental Laboratory. June 1985 to January 1989. SELECTED REFEREED PUBLICATIONS (LAST 3 YEARS) Mahoney, K. M., and G. M. Lackmann, 2006a: The effects of organized upstream convection on downstream precipitation. In Press, Wea Forecasting. 21. Mahoney, K. M., and G. M. Lackmann, 2006b: The Sensitivity of Numerical Forecasts to Convective Parameterization: A Case Study of the 17 February 2004 East Coast Cyclone. Wea. Forecasting. 21, 465– 488. Brennan, M. J., and G. M. Lackmann, 2006: Observational diagnosis and model forecast evaluation of unforecasted precipitation during the 24-25 January 2000 East Coast cyclone. Mon. Wea. Rev., 134, 2033– 2054. Brennan, M. J., and G. M. Lackmann, 2005: The influence of incipient latent heat release on the precipitation distribution of the 24–25 January 2000 U.S. East Coast cyclone. Mon. Wea. Rev., 1913–1937. Lackmann, G. M., and R. M. Yablonsky, 2004: On the role of the precipitation mass sink in tropical cyclogenesis. J. Atmos. Sci., 61, 1674–1692. Reeves, H. D., and G. M. Lackmann, 2004: The effects of diabatic processes on cold-frontal propagation. Mon. Wea. Rev., 132, 2864–2881. Brennan, M. J., G. M. Lackmann, and S. E. Koch, 2003: An analysis of the impact of a split-front rainband on Appalachian cold-air damming. Wea. Forecasting, 18, . Bailey, C. M., G. Hartfield, G. M. Lackmann, K. Keeter, and S. Sharp, 2003: An objective climatology, classification scheme, and assessment of sensible weather impacts for Appalachian cold-air damming. Wea. Forecasting, 18, . FIVE OTHER RELEVANT ARTICLES: Lackmann, G. M., K. Keeter, L. G. Lee, and M. B. Ek, 2002: Eta model representation of freezing and melting precipitation: Implications for winter weather forecasting. Wea. Forecasting, 17, 1016−1033. Lackmann, G. M. 2002: Potential vorticity redistribution, the low-level jet, and moisture transport in extratropical cyclones. Mon. Wea. Rev., 130, 59−74. Lackmann, G. M., and J. R. Gyakum 1999: Heavy cold-season precipitation in the Northwestern United States: Synoptic climatology and an analysis of the flood of 17−18 January 1986. Wea. Forecasting, 14, 687−700. Henderson, J., Lackmann, G. M., and J. R. Gyakum 1998: An application of potential vorticity inversion to the movement of Hurricane Opal. Mon. Wea. Rev., 127, 292−307. Bosart, L. F., and G. M. Lackmann, 1995: Postlandfall tropical cyclone reintensification in a weakly baroclinic environment: A case study of hurricane David (September 1979). Mon. Wea. Rev., 123, 3268–3291. SELECTED AWARDS, HONORS, AND PROFESSIONAL COMMITTEES AMS Editor's Award, Monthly Weather Review, 2002 Subject Area Editor: Mesoscale meteorology and NWP, Bulletin of the AMS (July 2006 to present) Associate Editor: Monthly Weather Review (January 1999 to 2003) NWS Award for Collaborative Research, October 2003 U.S. Department of Commerce Bronze Medal, Fisheries-Oceanography Coordinated Investigation, October 2002 Member, AMS Weather Analysis and Forecasting Committee, January 2001 – January 2004 Faculty Advisor: NCSU AMS Student Chapter, September 2000 to present

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LIAN XIE Professor Department of Marine, Earth and Atmospheric Sciences North Carolina State University Box8208 Raleigh, NC 27695 Phone: (919) 515-1435, Fax: (919) 515-7802 Email: [email protected]

EDUCATION: 7/1992: Ph.D. (Meteorology and Physical Oceanography), University of Miami, Miami, FL. 1/1985: M.S. (Meteorology), Nanjing Institute of Meteorology, Nanjing, China. . 7/1982: B.Sci., (Meteorology), Nanjing Institute of Meteorology, Nanjing, China. ACADEMIC APPOINTMENTS: 2005 --- present Professor, North Carolina State University, Department of Marine, Earth and Atmospheric Sciences, Raleigh, North Carolina. 2001 --- 2004 Associate Professor (tenured), North Carolina State University, Department of Marine, Earth and Atmospheric Sciences, Raleigh, North Carolina. 1998 --- 2001 Assistant Professor, North Carolina State University, Department of Marine, Earth and Atmospheric Sciences, Raleigh, North Carolina. 1992 --- 1998 Visiting Assistant Professor and Coordinator of Marine Science Ph.D. Program, University of North Carolina at Wilmington and North Carolina State University, Department of Marine, Earth and Atmospheric Sciences, Raleigh, North Carolina. 1987 --- 1992: Research Assistant, University of Miami, RSMAS, Miami, Florida. 1985 --- 1987: Assistant Lecturer, Department of Meteorology. Nanjing Institute of Meteorology, Nanjing, China. PROFESSIONAL SERVICES AND AWARDS: 1998: National Weather Service Certificate of Appreciation Award. 2003: National Weather Service Award for Collaborative Research. Co-Chair, Sino-US Workshop on Dust Storms and Their Effects on Human Health, Raleigh, NC. November 25-26, 2002 (Co-sponsored by NASA, NOAA, EPA, NIEHS, and USDA-Forest Services) Coordinator, International Forum on Environment, September 13-15, 2004, Beijing, China. 2000 – 2004: Editorial Board, Advances in Atmospheric Sciences. Science Advisory Panel: Beijing Urban Environment Research Program. 1998 – 2000: Associate Editor, Weather and Forecasting. 1996 – 1997: Member of U.S. Weather Research Program Prospectus Development Team on Landfalling Hurricanes (PDT5). 1995 – 1996: Member of U.S. Weather Research Program Prospectus Development Team on Coastal Meteorology (PDT3). 2002 – 2004: Departmental representative to the College of Physical and Mathematical Sciences’ Computer Committee, North Carolina State University. 2000 – present: Chair, Department of Marine, Earth and Atmospheric Sciences’ Computing and network Facility Committee. North Carolina State University. 2004 – present: Chair, Seminar Committee. Department of Marine, Earth and Atmospheric Sciences. North Carolina State University. 2006 – present: College Reappointment, Tenure and Promotion Advisory Committee Member of American Meteorological Society American Association for the Advancement of Sciences Member of Sigma-Xi.

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PUBLICATIONS (Selected from over 50 refereed publications) A. 5 Most Recent Refereed Publications: 1. 2. 3. 4. 5.

Peng, S. and L. Xie, 2006: Effect of determining initial conditions by four-dimensional variational data assimilation on storm surge forecasting. Ocean Modeling, 14, 1-18. Xie, L., S. Bao, L.J. Pietrafesa, K. Foley and M. Fuentes, 2006: A Real-Time Hurricane Surface Wind Forecasting Model: Formulation and Verification. Monthly Weather Review, 134, 1355-1370. Xie, L., Tingzhuang Yan, and Leonard Pietrafesa, 2005: The effect of Atlantic sea surface temperature dipole mode on hurricanes: Implications for the 2004 Atlantic hurricane season, Geophysical Research Letters, VOL. 32, doi:10.1029/2004GL021702, 2005. Guan, C. and L. Xie, 2004: A unified linear parameterization of the drag coefficient over the surface of the ocean. J. Physical Oceanography, 34, 2847-2851. Xie, L., L.J. Pietrafesa, and M. Peng, 2004: Incorporation of a mass-conserving inundation scheme into a three-dimensional storm surge model. J. Coastal Research, 20, 1209-1223.

B.

5 Other Recent Publications:

1.

Song, Y., F. Semazzi, L. Xie, and L.J. Ogallo, 2004: A coupled regional climate model for Lake Victoria basin of east Africa. International Journal of Climate, 24, 57-75. Xie, L., 2004: Air-sea interactions associated with mesoscale weather systems. In Observation, Theory and Modeling of Atmospheric Variability. X. Zhu edited, World Scientific Series on Meteorology of East Asia, World Scientific Publishing Co., 612pp. Xie, L., L.J. Pietrafesa, and K. Wu, 2003: A numerical study of wave-current interaction through surface and bottom stresses: Coastal ocean response to Hurricane Fran 1996. J. Geophys. Res., 108, (C2, 3049). Peng, M., L. Xie, and L.J. Pietrafesa, 2004: A numerical study of storm surge and inundation in the Croatan-Albemarle-Pamlico Estuary System. Estuarine, Coastal and Shelf Science, 59, 121-137. Bao, S., S. Raman, and L. Xie, 2003: Numerical simulation of the response of the ocean surface layer to precipitation. Pure and Applied Geophysics, 160, 2419-2446.

2. 3. 4. 5.

LIST OF CURRENT AND PAST GRADUATE STUDENTS Ph.D. students: Y. Liu, Q. Tang, X. Zhang, M. Xia, H. Liu, X. Liu, B. Wang, T. Yan, S. Bao, M. Peng, Y. Song, V. Manghnani, H. Jin. M.Sci. students: Elinor Keith, Joshua Palmer, Meredith Croke, Jamie Wirth, Peng Su, Neil Davis, Robert Bright, Douglas Schneider, Douglas Hilderbrand. PERSONS COLLABORATED IN THE PAST THREE YEARS Montse Fuentes, Leonard J. Pietrafesa, Earle Buckley, Frederick Bingham, Marvin Moss, John Morrison, Madilyn Fletcher, Carey Jang, Aijun Xiu, Paul Liu, Jing Lin, Fredrick Semazzi, Gary Lackmann, Al Riordan, David Dickey, Mike Kaplan, Yuh-Lang Lin, Sethu Raman, Thomas Karl, Mike Durako, Lynn Leonard, Dan Kamykowsky

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Matthew D. Parker EDUCATION Ph.D., Atmospheric Science, Colorado State University, August 2002 M.S., Atmospheric Science, Colorado State University, May 1999 B.S., Meteorology, Valparaiso University, May 1996 PROFESSIONAL EXPERIENCE Assistant Professor, North Carolina State University. August 2005 to present Assistant Professor, University of Nebraska-Lincoln, August 2002 to July 2005 REFEREED PUBLICATIONS FROM LAST THREE YEARS Storm, B.A.2, M.D. Parker, and D.P. Jorgensen, 2006: A convective line with leading stratiform precipitation from BAMEX. Mon. Wea. Rev. in press. Parker, M.D., 2006: Simulated convective lines with parallel stratiform precipitation. I: An archetype for convection in along-line shear. J. Atmos. Sci, in press. Parker, M.D., 2006: Simulated convective lines with parallel stratiform precipitation. II: Governing dynamics and associated sensitivities. J. Atmos. Sci., in press. Bryan, G.H., J.C. Knievel, and M.D. Parker, 2006: A multi-model assessment of RKW Theory's relevance to squall line characteristics. Mon. Wea. Rev., 134, 2772-2792. Kuchera, E.L., and M.D. Parker, 2006: Severe convective wind environments. Wea. Forecasting, 21, 595-612. Parker, M.D., I.C. Ratcliffe, and G.M. Henebry, 2005: The July 2003 Dakota hailswaths: Creation, characteristics, and possible impacts. Mon. Wea. Rev., 133, 1241-1260. Parker, M.D., and J.C. Knievel, 2005: Do meteorologists suppress thunderstorms? Radar-derived statistics and the behavior of moist convection. Bull. Amer. Meteor. Soc., 86, 341-358. Parker, M.D., and R.H. Johnson, 2004: Simulated convective lines with leading precipitation. Part I: Governing dynamics. J. Atmos. Sci., 61, 1637-1655. Parker, M.D., and R.H. Johnson, 2004: Simulated convective lines with leading precipitation. Part II: Evolution and maintenance. J. Atmos. Sci., 61, 1656-1673. Parker, M.D., and R.H. Johnson, 2004: Structures and dynamics of quasi-2D mesoscale convective systems. J. Atmos. Sci., 61, 545-567. OTHER RELEVANT PUBLICATIONS Parker, M.D., and D.A. Ahijevych, 2006: Convective episodes in the east—central United States. Mon. Wea. Rev., submitted. Billings, J. M., and M. D. Parker, 2006: Evolution, maintenance, and propagation of an elevated MCS. 23rd Conference on Severe Local Storms, 6–10 November 2006, St. Louis, MO, accepted. French, A. J., and M. D. Parker, 2006: Multiple modes of convection in moderate-to-high shear environments. 23rd Conference on Severe Local Storms, 6–10 November 2006, St. Louis, MO, accepted. Parker, M. D., 2006: Idealized simulations of nocturnal severe wind-producing convective systems. 23rd Conference on Severe Local Storms, 6–10 November 2006, St. Louis, MO, accepted. Parker, M. D. and R. H. Johnson, 2000: Organizational modes of midlatitude mesoscale convective systems. Mon. Wea. Rev., 128, 3413-3436. SELECTED AWARDS, HONORS, AND PROFESSIONAL COMMITTEES Program Committees for 23rd and 24th AMS Conf. on Severe Local Storms (committee co-chair for 24th), and AMS 2005 Symposium on the Challenges of Severe Storms, 2004-2008 AMS Committee on Severe Local Storms, 2004-2007 Associate Editor, Monthly Weather Review, 2004-2006 Visiting scientist, Hazardous Weather Testbed, Storm Prediction Center/National Severe Storms Lab., 2005 Reviewer and consultant for NWS-RAH mesoscale convective system procedures, 2006

2

Students are underlined in the publications list.