Early analysis

The 00 UTC NAM model is in, as we watch supercell thunderstorms produce tornadoes in eastern Oklahoma tonight.

The storms will move eastward overnight, as a strong upper level low and associated cold front/dryline move east.  The dynamics will be very impressive over Mississippi and Alabama tomorrow, as SE winds blow towards the surface low, and winds veer with height and increase in speed, creating helicity values over 400 m2/s2 over most of northwest Alabama by early afternoon, shifting to central and east Alabama during the afternoon.

The limiting factor for a major tornado outbreak in Alabama may be instability.  The air is dry now with dewpoints in the lower 50s.  However, as winds pick up out of the south aloft tomorrow morning, dewpoints in MS and west AL will rise into the 60s, producing CAPE values that increase rapidly during the afternoon, especially from Fayette and Tuscaloosa west.  The best chance for a tornado outbreak will probably be in eastern Mississippi and western Alabama.  It is possible that the higher dewpoint air won’t make it as far north in BHM and ANB, and the warm advection may also produce low clouds, keeping temperatures below 70.  If this is the case, the storms will mainly come in as a squall line east of I-65.  But, things could still change, and tornadoes will be possible over all of Alabama tomorrow.  If the sun is out for several hours tomorrow and we climb to 75 or 80, it could get bad.

Have a source of weather information handy tomorrow.  Things may get going as early as noon in west Alabama, and reach BHM between 2 and 5 pm.  This is still a developing weather situation, so have a tornado plan ready.

Category: Severe Weather