The focus of this research is on continued studies of organized convective weather systems that occur primarily during the warm season in the vicinity of the Great Lakes. Specifically, the research is targeted at mesoscale convective systems (MCS) and embedded mesoscale convective vortices (MCV) as well as intense quasi-linear convective systems know as derechos. Derechos often appear as bowing line segments in operational Doppler radar imagery. Derechos and MCVs were the major focus of the Bow Echo and Mesoscale Convective Vortex Experiment (BAMEX). The research builds on opportunities from BAMEX. Specific research tasks include: 1) establish how the vorticity fields associated with the MCV and the triggering upper-level disturbance reorganize and scale upward after deep convection begins, 2) assess MCS/derecho life cycle sensitivity to the structure of the triggering upper-level forcing disturbances and the extent of surface boundary, pre-existing and convectively driven, interactions, 3) investigate MCV/MCS/derecho structure and life cycles through new diagnostic analyses that take advantage of available higher spatial and temporal resolution gridded datasets 4) employ the state-of-the-art Weather Research and Forecasting (WRF) model to simulate MCV life cycles and compare MCV development with incipient tropical cyclone development, 5) perform WRF model simulations of real and idealized MCS/derecho events to assess at what point larger scale forcing becomes unimportant and when storm-scale dynamics becomes dominant, and 6) expand an ongoing research effort targeted at developing a better understanding of the physical mechanisms that govern warm season severe weather (convection) events that occur over the Great Lakes.
The research will be facilitated by the availability of high resolution, global, gridded analyses from operational forecast centers. Advantage will also be taken of the gridded 13 km analyses form the NOAA Regional Update Cycle (RUC) system. The availability of hourly surface and upper air RUC analyses over North America will permit an investigation of the life cycles of long-lived MCVs and derechos. These analyses when coupled with the special BAMEX datasets and simulations from the WRF model will permit more comprehensive research investigations of important convective weather events through multiscale case studies than has been previously possible.
In terms of broader impacts, existing weather prediction models do a relatively poor job of simulating convective mode and life cycles properly. In this regard, the operational weather prediction models are limited in how well they can forecast severe weather. The results from the research will add to new knowledge of severe weather events. The graduate students trained and supported under this project will facilitate the transfer of research knowledge to operations as they pursue careers in the field after graduation. This project also presents the opportunity to work with various government agencies (e.g., the NOAA Storm Prediction Center) and other educational institutions to help facilitate the transfer of research knowledge to operations and students.
: NSF ATM-0646907 This grant provided research support for an investigation of how the Great Lakes influence the development and evolution of clusters of severe weather-producing thunderstorms in the vicinity of the Great Lakes during the warm season. Temperature differences between the relatively cool waters of the Great Lakes and the warmer surrounding land surfaces during the warm season can result in the formation of distinctive boundaries near the Great Lakes that separate lake-chilled air from land-heated air. These surface boundaries in turn can serve as a focus for thunderstorm development when warm, humid air masses drawn toward the Great Lakes are forced to ascend over the surface boundaries. The research supported by this grant determined that the western boundary of Lake Michigan and the southern boundary of Lake Superior could often serve as a focus for new thunderstorm formation and subsequent severe weather development. The research supported by this grant also determined via detailed analysis of individual events and numerical modeling studies of selected events that multiple thunderstorm complexes over the Midwest in the vicinity of the Great Lakes could interact with one another so that outflow boundaries produced by an initial thunderstorm complex helped to determine the location and intensity of subsequent thunderstorm complexes. In the area of broader impacts, the research conducted under this grant supported the completion of two Ph.D. theses and one M.S. thesis. It also supported a serendipitous research opportunity by a fourth graduate student that was related to the focus of the original research. These four graduate students have since graduated and all of them are working in the field (two of these students have or are starting academic jobs and two of them have or are starting research jobs). All four students benefitted educationally through travel support that made it possible for them to present their research findings at professional conferences and workshops and thereby become known in the field. The PI incorporated the new research finds supported by this grant into his undergraduate and graduate classes.
