2002 Annual

Wednesday, 16 January 2002: 4:00 PM
An identification of factors discriminating between significant and extreme heavy rainfall events
James T. Moore, Saint Louis University, St. Louis, MO; and C. E. Graves and S. Ng
Heavy convective rainfall has a significant impact on the local environment including agricultural, economic, and societal effects. Whereas a significant (2-4 inches in 24 h) rainfall event may produce localized flooding, an extreme (6-10 inches in 24 h) rainfall event will produce flash flooding with catastrophic consequences. The impacts also vary according to the spatial rainfall distribution and antecedent conditions. Distinguishing between the synoptic/mesoscale environments associated with significant and extreme convective precipitation events is not a straight-forward task. In this study we compare two heavy convective rainfall events which took place over the same geographical region and time of year. The motivation of this study is to ascertain the distinguishing factors which discriminate between a significant and extreme convective precipitation event. In this diagnostic study, we examine the pattern and intensity of important processes associated with the development and maintenance of heavy convective rainfall. We will discuss the role of the low-level jet, surface-based boundaries, storm-scale interactions, moisture convergence, equivalent potential temperature, and instability in organizing a mesoscale convective system leading to significant versus extreme precipitation amounts.

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