RAL Seminar Series - Eric Hoffman

Wednesday, June 25, 2014
FL 2 - Room 1001
10:30am

Influence of Terrain on Warm-Season Convection in Northern New England

Eric G. Hoffman
Plymouth State University
Plymouth, NH

Abstract

Several studies have shown that flow over terrain can have a significant influence on the development and spatial distributions of thunderstorms. In order to understand the influence of terrain on thunderstorms in northern New England, a five-year climatology (2003-2007) of thunderstorm cells is constructed for the Gray, ME (KGYX) WSR-88D radar domain. The SCIT algorithm is used to identify and track all cells that occur within a range of 25 to 125 km of KGYX and have a minimum reflectivity of 50 dBz and VIL of 23 kg/m2.  Once identified, the cells are classified by the direction of the 700 hPa flow.  Results show that the majority of thunderstorms occur with a westerly flow component over and downstream of the mountains. In addition, there are distinct preferred areas for thunderstorm initiation and activity for different background flow directions. Radar reflectivities for each thunderstorm day in the five-year data set are subjectively examined to identify cases of isolated cell development.  Several case studies of these thunderstorm days with isolated cells are investigated to understand the physical mechanisms that lead to the unique spatial distribution of thunderstorm development and activity for each flow direction. The results from the case studies show, in general, that the low-level moisture and instability to the lee of the mountains is uniform and sufficient for thunderstorm development. Thunderstorm cells tend to develop in areas of weak lee troughs and surface convergence that are different for each flow direction.  The behavior of convective lines as they interact with terrain in northern New England is the subject of ongoing research.

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Eric Hoffman

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1001

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Wednesday, June 25, 2014 - 10:30am