Saturday, March 03, 2007

Thursday March 1, 2007 Tornadoes - Part One

Alabama residents who pay attention to news and weather had been hearing for days about the possibility of severe weather on Thursday March 1, 2007. During the morning hours of Wednesday February 28, 2007, the Storm Prediction Center placed a large area of the country, including all of Alabama, under a moderate risk of severe weather. They also mentioned the possibility that the risk could be upgraded to "high" for parts of Alabama and Mississippi the next morning.

Just after midnight in the early morning hours of Thursday, the SPC placed virtually all of Alabama and eastern Mississippi under a rare high risk of severe weather. Generally forecasters were saying that the morning would begin with non-severe storms, associated with a warm front. Conditions for severe weather were projected to be in the 11 a.m. to 6 p.m. time frame depending on which part of the state you were in.

Dew points had been rising through the 40's overnight. Scattered storms developed in Alabama around daybreak. These storms produced several reports of small hail, but wind fields were not yet favorable to cause the storms to rotate. As the Birmingham NWS described them, these storms were a "nuisance" compared to what was expected during the afternoon.

For a couple of weeks computer weather forecasting models had been projecting a powerful low pressure system to trek from northern Texas to Iowa. This low was forecast to drag a cold front through the Midwest and South. Ahead of the cold front, a warm front would serve to replace the cool dry airmass with a warmer, moister airmass. Temperatures were forecast to be around 70 with dewpoints over 60 throughout the state and over 65 in the southern half of the state. Above all of these surface features was a stong jet stream out of the southwest. Surface winds at the same time were expected to be stong out of the south.

All of the parameters were in place for an outbreak of tornadoes, including a couple of violent tornadoes. And that is what was forecasted.

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