Sunday, April 25, 2010

From Trough to Tornadoes

Until this week, severe weather season was off to a slow start across the central and eastern U.S. Relatively cool Gulf of Mexico waters and a high riding jet stream kept much of the region unusually warm and dry. What storms developed, deprived of a jet stream punch, were fairly mild and the seasonal tornado count was well behind average.

Then, early this week, a deep trough developed across the western U.S.; produced by a dip in the jet stream, cold air invaded the region, bringing mountain snows and chilly rain to the lowlands. Gaining strength as it crossed the Rockies, the storm emerged onto the High Plains, dropping hail along the Front Range and igniting tornadic thunderstorms ahead of its trailing cold front, in West Texas. While the central low has crept eastward across Colorado and Kansas, its cold front has billowed through the Southeast; fed by copious Gulf moisture and energized by the jet stream, powerful thunderstorms, producing heavy rain, frequent lightening and tornadoes, blossomed in the warm sector, just ahead of the front.

Yesterday, this squall line pushed across the lower Mississippi Valley, bringing destructive storms to Mississippi, Alabama and Tennessee; this morning, with the central low spinning over northern Missouri, the potent storms have shifted into the Florida Panhandle, Georgia and South Carolina. Here in Missouri, after a two-day deluge, we are left with chilly, wrap-around showers, gray skies and the relief of having dodged a bullet.