Thursday, 6 August 2015: 10:45 AM
Republic Ballroom AB (Sheraton Boston )
A nocturnal maximum in rainfall and thunderstorm activity over the central Great Plains is widely documented, but the mechanisms for understanding the development of thunderstorms over the region at night are still not well understood. Elevated convection, defined by Colman (1990) as storms formed through ascent above frontal surfaces, is one explanation, but this research shows that many thunderstorms can initiate at night without the presence of an elevated frontal inversion or nearby surface boundary. This study documents convection initiation (CI) events occurring at night over the central Great Plains from 1996 through 2014 during the months of April through July. Storm characteristics such as storm type (defined as linear, areal, or single cell), storm motion, initiation time and location, and others were documented. Once all of the cases were documented, surface data were examined to locate any nearby surface boundaries. The event's location in relation to these boundaries (if they existed) were documented. Three main modes of CI were identified: formation on a surface boundary, formation on the cold side of a surface boundary, and formation without the presence of a surface boundary. A climatology of these events will be presented. There appear to be two peaks of frequency of occurrence of CI at night: one early at night and one later. The later peak is due mainly to the events that form in the absence of a nearby surface boundary. Case studies also will be presented with emphasis placed on the more interesting, and less known, events that form without the presence of a nearby surface boundary.
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