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Prospective graduate students: We will hopefully be hiring one new student to work on the VORTEX2 project, starting in Fall 2009. Please contact Dr. Parker for more information. VORTEX2: Mobile Upsonde Measurements and Studies of Lower Tropospheric Processes Funding source: National Science Foundation The goal of this project is to acquire mobile upsonde measurements during the field phase of the Verification of the Origins of Rotation Experiment 2 (VORTEX2), and to use these data and numerical simulations: a) to understand the role of cold pool (outflow) dynamics in supercells and tornadogenesis; and, b) to understand storm-environmental interactions in mature supercells in terms of the near-storm lower tropospheric lapse rates. Recent climatologies and process studies have revealed the apparent importance of supercells' outflow temperatures, as well as lower tropospheric vertical wind shear and lapse rates, to tornadogenesis. However, there are still causal links missing from the chain of physical processes that lead to supercellular tornadoes. This lack of knowledge is important because, without it, the ability to forecast and produce timely warnings for tornadoes (and to avoid false alarms for non-tornadic storms) is unlikely to improve. Integrated Studies of Recurring, Non-Traditional Mesoscale Convective Systems Funding source: National Science Foundation The goal of this project is to determine the mechanisms governing the organization and maintenance of recurring, non-traditional mesoscale convective systems (organized groups of thunderstorms, "MCSs") by using numerical simulations and observational analyses. MCSs produce much of the warm season rainfall in the agriculturally vital Great Plains, as well as widespread hazardous weather. Recent work has revealed two recurring MCS structures that are poorly understood---convective lines with leading stratiform ("LS") and with parallel stratiform ("PS") precipitation---both of which frequently produce flash flooding. Recent work under this project has elaborated the elemental mechanisms for development and maintenance of LS and PS systems. However, such mechanisms are still unclear for elevated (not surface-based) MCSs, despite the fact that many of the MCSs that occur in the central U.S. are nocturnal, and often presumed to be elevated. This lack of knowledge is important because, without it, the ability to forecast precipitation and hazardous weather from these recurring convective modes is unlikely to improve. In addition to our work on elevated convection, other ongoing efforts are directed toward understanding how the mechanism and pattern of convective initiation may constrain the convective modes that emerge in moderate-to-high shear regimes (in which LS MCSs, PS MCSs, and supercells are all observed). CSTAR: Improving Understanding and Prediction of Warm Season Precipitation Systems in the Southeastern and Mid-Atlantic Regions Funding source: National Oceanic and Atmospheric Administration, Collaborative Science, Technology, and Applied Research (CSTAR) program Collaborators: Dr. Gary Lackmann, Dr. Lian Xie This project involves applied research with the goal of improving understanding and prediction of a set of high impact meteorological phenomena including landfalling tropical cyclones (TCs), convection, and orographically driven weather systems. Our 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). There are four primary areas of emphasis: 1) prediction of tornadoes and tornadic environments associated with TCs with 0-24 h lead time, 2) forecasting of inland flooding and non-tornadic winds associated with TCs, 3) TC storm surge forecasting, and 4) character of convective systems in the eastern U.S. and their interaction with the Appalachian Mountains. The Convective Storms Group is primarily responsible for items 1 and 4. Tornadoes and tornadic environments associated with TCs. 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 emphasis is upon improved anticipation in the 3-24 h time frame, in addition to the nowcasting aspect. Convective systems in the eastern U.S. 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; in this project we 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 a convective system approaches 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 goal is to determine which environmental factors control this process. Improving the Representation of Organized Convection in NWP Models Funding source: National Science Foundation Collaborators: Dr. Gary Lackmann The goal of this project is to improve the convective and microphysical parameterizations that directly impact the motion of mesoscale convective systems (MCSs) and their associated impacts on larger-scale moisture transports and quantitative precipitation forecasts (QPF). Despite continuing advances in numerical weather prediction (NWP), limitations in the ability of numerical models to accurately represent convective systems are widely recognized. Current numerical models have difficulty representing processes such as interactions between convective parameterization (CP) schemes and model grid scale processes; convective-scale momentum, heat, and moisture fluxes; and the motion of MCSs. These problems, in turn, are linked to difficulties in the prediction of convection's impacts upon the larger-scale environment. In part because of these limitations, many NWP efforts are now utilizing explicit convection (EC) model configurations. However, many of the other physical parameterizations in NWP models, including PBL and microphysics schemes, were specifically developed for use in models with CP schemes. Therefore, omitting CP schemes in EC models may actually result in unforeseen consequences, yielding convective forecasts that are still not accurate.
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