Tornado potential Saturday?

It continues to feel like April in Alabama, with temperatures in the mid 70s. Dewpoints are now near 70, as Caribbean air is being pulled into Alabama! The fog this morning was incredible in some areas.

Trajectories showing where air that will be here tomorrow is coming from

La Nina continues to cause strange weather setups in North America. Check out these maps for 6 pm tomorrow. If one were to take the route that I and my business partner JP Dice took last Summer to see a decommissioned missile silo in Cooperstown, ND, temperatures would progress like this: 71 BHM, 37 St. Louis, 4 Des Moines, IA, -13 in ND. That is an 84 degree temperature difference! This is not normal, and when the temperature contrast gets this large, it is baroclinically unstable and any upper disturbance will intensify, form a surface low, and drop cold air south and take warm air north. Note the 160 mph jet stream! The cold air will move in on Sunday, with temperatures falling below freezing, and barely getting to 40 on Monday.

When it is this warm and humid at New Year’s Day, and a big dynamic system is headed our way, the threat for tornadoes and severe weather is a concern. A line of storms, some with damaging winds and the possibility of small tornadoes, will move through Alabama Saturday night. The question is whether or not any discrete supercells, like the one that caused a tornado at Lay Lake Wed night, will form out ahead of the line. Here is the deal…it is very warm and humid at the surface, but it is not that cold aloft, and many computer models suggest a layer of warm air near 4,000 feet (circled below) that would suppress most thunderstorm activity until the main line arrives late tomorrow night. However, if that warm layer does not materialize, with unstable air and high wind shear, we could see some tornadoes tomorrow afternoon and evening over northern and central Alabama. Doubtful, but we can’t rule it out right now.

NAM model prediction for BHM for 3 pm tomorrow

Tomorrow is a day to keep an eye on the weather. Either way, a line of storms with potentially damaging winds will move through around midnight tomorrow night. Make sure you have two sources of weather information, and go over your tornado safety plan if you didn’t the other night.

Dr. Tim Coleman

Consulting Meteorologist

Coleman Knupp and Dice LLC

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