The Spectrum of Progressive Derecho Formation Environments

Corey F. Guastini & Lance F. Bosart
Dept. of Atmospheric & Environmental Sciences
The University at Albany / SUNY

20 May 2014, 4:00 PM

National Weather Center, Room 1350
120 David L. Boren Blvd.
University of Oklahoma
Norman, OK

Progressive derechos are severe mesoscale convective systems that often form during the warm season (May–August) in benign synoptic environments east of the Rocky Mountains and, by definition, cause straight-line wind damage along paths upwards of 400 km long. This presentation will expand upon existing derecho climatologies with a warm season, 1996–2013 progressive derecho climatology highlighting spatial and temporal frequencies of progressive derechos over the 18-year span.

The presentation will also include results from the application of a subjective, seven-category classification scheme for progressive derecho synoptic initiation environments including derecho-relative composites of fields pertinent to progressive derecho formation.

Finally, case studies will be presented of two progressive derechos on opposite ends of the progressive derecho formation spectrum, one forming on the evening of 12 June 2013 ahead of a well defined upper-level trough and surface cyclone, and the other along a weak, east-west oriented surface boundary on the morning of 29 June 2012 in the absence of substantial large-scale forcing for ascent. Maintenance and demise of the two derechos will be linked to the distinct synoptic classes they represent.

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