December Tornadoes

Over the past week, an atmospheric ridge developed across the eastern U.S., allowing warm, humid air to flow northward from the Gulf of Mexico.  Yesterday, a potent storm system, centered over Iowa, swept its cold front into this unstable air mass, igniting severe thunderstorms, unleashing torrential rain and spawning tornadoes.

While tornadoes are not rare in the Gulf Coast States during the winter months, yesterday's outbreak, which included 24 twisters, was unusual for December.  As of this morning, at least seven deaths have been attributed to the storms, which pummeled communities from Arkansas into Mississippi and Tennessee and northward to the Ohio Valley.

As the cold front continues to push eastward this morning, the risk of severe weather persists through eastern Alabama, northern Florida, Georgia and the Carolinas.  This week's atmospheric imbalance in the U.S., characterized by a strong jet stream that divided cold, dry air in the West from warm, humid air in the East, was bound to break down and, when it did, tragic consequences ensued.

Addendum:  As of December 25, the storm system death toll has reached 14.  In addition, meteorologists suspect that a significant percentage of the twister sightings were related to the same long-lasting tornado, that may have been on the ground over a distance of 145 miles (from Clarksdale, Mississippi, into west-central Tennessee).