Quick Update at 8 a.m.: New Tornado Watch to the West, Line Intensifying over Mississippi as Expected

The SPC and local National Weather Service offices did issue a tornado watch for eastern Mississippi and southeastern Louisiana as the thunderstorms have ramped up impressively along and west of I-55 in Mississippi and Louisiana.

Severe severe thunderstorm and a few tornado warnings are in effect along the line from just east of Jackson back to the coast south of Lafayette in Louisiana.

Surface-based CAPE values according to the SPC Meso page are 500-1500 j/kg over Southwest Alabama, but the morning sounding at Birmingham clearly shows 818 joules of surface based CAPE already. This means the instability is higher already and only going to get higher this morning as we get some surface heating.

And surface winds are backed, out of the southeast, over eastern Mississippi and much of Alabam, increasing the low-level helicity. Those values are running 300-400 m2/s2 across West Alabama which is sufficient low-level shear for tornadoes. Bulk shear values are 35 knots and will be increasing through the day, meaning storms will be better organized as we go through time. We are already seeing that on the storms in Mississippi and Louisiana.

Dewpoints are already at or above 65F for areas west of I-65, with some upper 60s and even 70F readings back int Mississippi and over coastal Alabama.

Using extrapolation, the storms will reach West Alabama in about 3.5 hours, or around 11:30 a.m. This would put them into Tuscaloosa by 1:30 or so, which is of concern for the Air Show, which has changed its schedule already in anticipation of the weather. We will have to keep timing the storms out to see if they stay on schedule. They can be a little like an AMTRAK train when it comes to keeping to a schedule.

The SPC day one outlook is basically unchanged.

Over Northwest Alabama, the lead storms have weakened, with just rain, lightning and gusty winds moving across eastern Marion, eastern Franklin, eastern Lauderdale and Colbert and into Larence and Limestone counties.

there are some showers that have developed ahead of the main line from Huntsville down to Cullman and Tuscaloosa. There is a little lightning around Culllman, but these showers and storms aren’t significant.

Tags: exp03

Category: Alabama's Weather, ALL POSTS