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University of Utah: "Weather prediction over complex terrain"

Final Report

The primary focus of this project is the prediction of local and mesoscale circulations along the front range of the Wasatch Mountains. Strong downslope winds, orographically-enhanced precipitation, and lake-effect snowstorms are examples of weather events that result in considerable damage and occasional fatalities in the area. The objectives are to assess the feasibility of deterministic local weather prediction in the vicinity of Salt Lake City and to develop a conceptual model for how these mesoscale phenomena develop in response to synoptic scale flow interactions with the terrain. The principal differences between this approach and the forecasts already being made at NMC are that they will resolve much smaller horizontal scales (5 km to 30 km) and incorporate more detailed treatment of planetary boundary layer processes.

The research described above uses the forecast model developed by Berry and Paegle. The model has been modified to include explicit stable precipitation and moist convective adjustment; radiation upper boundary conditions; and nudging at the lateral boundaries on the basis of output from the Nested Grid Model and Eta model. One of the significant accomplishments of this effort has been the twice-daily transmission of graphical output from numerical mesoscale forecasts from the University of Utah to the Salt Lake City forecast office. These forecasts have been cited frequently by the forecasters as having provided insight into the dynamics and temporal evolution of storms over Utah.

Funding from COMET was used primarily to support a graduate student whose master's thesis was based on a case study in which the model was used to investigate the dynamical processes that took place during a major winter storm. The student is now employed by the NWS in Oregon. Several other NWS employees have also undertaken studies at the university, strengthening the collaboration even further.