Tornado threat

SPC continues to have most of Alabama in a moderate risk for severe weather today and tonight. This is a very complex system, and it is possible that there will be two areas of severe weather we have to deal with today.

Early this morning, the moist unstable air is located over SE Alabama, and thunderstorms have developed there. Those may continue for a few hours, and with wind shear, there could be an isolated severe storm this morning with this area of storms, mainly SE of I-59.

The main storm system is moving through Oklahoma and north Texas this morning, with a sharp upper-level trough and surface low.

500 mb

Surface pressure

Temp and dewpoint (shaded)

The approaching surface low will be associated with helicity, or when winds change direction and increase speed with height. This allows storms to rotate (the winds changing with height produces rotation in the horizontal, like a spiraling football. When a storm tilts this rotation upward, like the football getting tipped into the air, the rotation becomes oriented vertically, like a tornado). However, the air over NW AL into MS and TN is dry and stable so far. It looks like the strong winds ahead of the low will transport moist air into the area ahead of the low later today, and severe storms will develop west of the Mississippi River late this morning, and move into Alabama by this afternoon. Wind shear will be very strong, so tornadoes are likely over Alabama by this afternoon.

Please have a source of weather information nearby today and tonight, and think about what you would do if a tornado warning is issued.

We are headed out for a storm chase later this morning, including the new UAH mobile Alabama X-band radar (MAX). Since we didn’t get to go Saturday, my wife Jennifer is going along, also…this will be her first storm chase. We will make a decision or where to go around 800 am, but it looks like I-22 toward Tupelo or US 82 toward Columbus, MS may be a good start. I’ll try to send blog updates or video from the field.

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