9700626 Koch Progress in forecasting of precipitation and severe weather associated with mid-latitude cyclones has been slow, compared to advances in understanding and ability to forecast the synoptic-scale aspects of cyclones. A major reason for this has been the lack of data with sufficient spatial and temporal resolution to resolve mesoscale processes associated with precipitation bands. One of the mesoscale phenomena that has been suggested to play an important role in the formation and modulation of precipitation bands is mesoscale gravity waves. Gravity waves present a real challenge to weather forecasters, because they have been nearly impossible to detect with standard synoptic observations and are not routinely predicted by operational models. The major observational and modeling improvements being brought about by the National Weather Service Modernization now affords the opportunity for the research and operational meteorological communities to work together to develop improved understanding of these mesoscale phenomena. Additional research is needed on wave dynamics and generation mechanisms, and to differentiate them from the presence of other mesoscale phenomena, notably cold fronts aloft A definitive identification of gravity wave generation mechanisms and vertical structure, their interactions with convection, and their role in the cyclogenesis process remains elusive. One cause for this confusion is that the evidence often suggests more than one mechanism may be operative. Recent research by the Principal Investigator has focused on understanding the forcing, dynamics, and vertical structure of weather-producing mesoscale gravity waves using primarily surface, wind profiler, and mesoscale model data obtained during the STORM-FEST project. The Principal Investigator has found there to be a predilection for strong waves to be generated in regions of dynamic imbalance during lee cyclogenesis as a jet streak encounters the Rocky Mountai ns. However, in at least one of these cases, the evidence also suggests that a cold front aloft occurred in close proximity to the waves. The research to be performed under this award represents both a continuation of the Principal Investigator s past efforts and an extension into new but related directions. The ultimate goal is to incorporate observed precipitation band structure and dynamics into a new conceptual model for lee cyclones in the central U. S. The first objective is to resolve the role of cold fronts aloft versus gravity waves, or perhaps their interactions, in the generation of rainbands. Secondly, the research will help to remove ambiguities concerning the role of unbalanced dynamics in gravity wave formation. The third objective, will be to address the issue of mesoscale predictability, in terms of what data and data assimilation techniques are required for mesoscale models to reliably produce observed gravity waves. Lastly, the Principal Investigator will complete an ongoing investigation of solitary waves and bores generated by cold fronts. Results from this research potentially will have direct and immediate impact on the ability to predict mesoscale gravity waves. ***
