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Iowa State University: Forecasting nocturnal mesoscale convection over the Great Plains

Final Report

One of the most challenging forecast problems over the Great Plains is the prediction of the development and intensification of nocturnal convection. It has long been recognized that thunderstorms are more common at night than during the day over this region. This contradicts our usual view of thunderstorms being promoted by daytime heating.

One reason for the anomalously high frequency of nocturnal thunderstorms over the Great Plains is the relationship between convection and the nocturnal low-level jet (LLJ) that commonly occurs over the plains. Related work, which was conducted under an earlier Outreach Partners Project, included the analysis of case studies of these interactions between the LLJ and mesoscale convection. During the project, a data set containing all of the hourly profiler wind observations for 1991 and 1992 was collected, and an hourly climatology of the LLJ was developed.

Because mesoscale convection over the Great Plains is a regional problem that requires a regional perspective, three NWS forecast offices participated in this Outreach Cooperative Project (Des Moines, Minneapolis, and Chicago). Research activities accomplished as part of the project includes the following: