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2019-03-03 EVENT: AR/LA/TN/MS/AL/GA

MikeD

EF1
Joined
Oct 10, 2017
Messages
86
Location
Miami
Weak CAPE on Sunday. Solid amount of wind shear (80-95kts in the upper atmosphere), but not enough directional for a major event. Standard severe storms ahead of the surface wave/squall line.

Looks more like a jumble of storms than discrete supercells. Not a very good birthday.
 
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A consensus from the 12z Euro/GFS suggests sufficient instability on the order of 750-1500 J/kg SBCAPE across much of the Gulf Coast states, especially near/south of I-20. Although surface winds appear a bit veered at SSW, note that 500mb are more westerly than the last event, so there is some enlargement of hodographs.

While this may not be a big supercell outbreak, I wouldn’t be suprised if there are a few supercells across the southern two-thirds of MS/AL, given rich boundary layer moisture, substantial wind shear and at least modest surface-based instability.
 
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If it weren't for the crashing cold front on this setup, the environment looks pretty decent for Dixie Alley. Good CAPE, good shear, good moisture etc. Quite a temperature difference with the front though. A quick look at the NAM nest shows the front laying through Central Alabama back into Louisiana by mid afternoon with 40s on the northwest side of the front and 70s southeast of it. Unfortunately this isn't a warm front and its crashing southeast. There might be a chance toward evening across SE MS/SW AL for a supercell or two to tap into the good environment, however this is highly conditional on the frontal position and movement. Right now, I don't see anymore than a squall line with damaging winds, maybe an embedded tornado or two, and flooding risks. That area doesn't need any more rainfall in the near term.
 
For MS/AL I agree, but for GA, I think things look a bit better. NAM NEST is showing spots with SIGTOR up to 4 around 22z on Sunday. But it's also showing some junk out ahead of the main line which could limit instability in advance.
 
Well, the models this morning are still showing a chance for activity between Columbus, GA and Macon, GA and to the east so that's where I'll be chasing.
 
Sunday is another Dixie day I did not chase, but maybe should have. Boundary analysis won the day for forecasters and chasers; however, the day is soured by the loss of life.

Hats off to SPC for sticking with hatched tornado, in spite of CAMs slop and lines. Maybe it could have been MDT and/or swapped with the prior Saturday. Good people can debate the precision; however, I say SPC was accurate both days. SPC forecasted sig tor.

Behind the severe indices were the mesoscale details. Surface winds were only slightly veered; however, well backed right along the lifting Georgia warm front (formerly coastal front / synoptic WF was Carolinas). 850 mb chart showed strong winds but a little veered; however, 925 mb was backed in Georgia. Basically one had to be well ahead of the 700 mb trough (better hodos) because things were veered right under the 700 mb trough. Therefore, Georgia and far east Alabama made sense as a chase target more than farther southwest. Still for the public and for coverage, the SPC outlook was good.

Farther up the atmosphere the speed shear was obvious all along. I could not get over the positive tilt though. Once again cold rain in Chattanooga did not give me the feeling either, even though I knew South Georgia would destabilize. I'm just sorry for the victims.
 
Right after I posted the above question, I saw Jon's analysis with photos on Facebook, posted by his wife, Shawna. I now see why there weren't many images.
 
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