Sunday, 22 January 2017
4E (Washington State Convention Center )
The current method to predict flash flooding is through real-time rainfall rate estimates that are inaccurate despite advances in radar technology. However, under certain circumstances other indicators may aid in the detection of heavy, convective rainfall. This research assists forecasters in recognizing one specific pattern that leads to flash flooding: the collapse of a prominent hail column. Trends in time and location differences between positive CG lightning strikes, hail indicators, and flash flooding reports appear to indicate transitions of convection and a new method for predicting heavy, convective rainfall. Investigated cases were limited to the Northeastern United States, specifically Pennsylvania, New Jersey, New York, and the New England states. In addition, cases were determined between the months of May to August, 2008-2014. 39 cases were identified as having a transition from “severe-producing” to “flood-producing” convection, based on Storm Data reports and physical indicators. The average time and location difference between hail indicators and +CG lightning strikes was 21 minutes and 15.320 km. The average time and location difference between +CG lightning strikes and flash flooding was 40 minutes and 13.765 km. Identifying these transitions in real time could mean better predictions of flash flooding and offer more time to warm the public of probable severe weather.
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