Spectrum of Progressive Derecho Formation Environments
Noon August 26th in room 2155
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 cause, by definition,
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
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.