Severe WX Severe Threat 25 March 2021

[tennessee storm chaser]

Both those analogs are from 5/4/2003...MKC is Kansas City which had two F4s and several weaker but still significant tornadoes pass nearby on that day.

My town Jackson tennessee we had a ef4 that day... May 4 2003

 

[MattW]

Wow! This what the NAM is saying for 10 miles WSW of Reform, AL at 19:00 CDT Thursday!

 

[Kory]

The NAM has looked a little too flat with the energy to actually utilize a good portion of the STP map I've seen posted. Like I said yesterday, it appears the GFS/NAM are narrow corridors where we may see some severe weather. Now, the Euro/UKMET on the other hand are much more potent looking...that would be a much more widespread severe weather event verbatim.

I should note the Euro/UKMET combo are hard to bet against.

 

[HazardousWx]

Hate to cry wolf again on this one. Seems like we are at the northern edge of the enhanced here in Huntsville, like we were last week. All we got was rain.

 

[The Nino]

Hate to cry wolf again on this one. Seems like we are at the northern edge of the enhanced here in Huntsville, like we were last week. All we got was rain.

is this the same setup as last system? CAD and wedge dominating our area?

 

[Kory]

Hate to cry wolf again on this one. Seems like we are at the northern edge of the enhanced here in Huntsville, like we were last week. All we got was rain.

Completely different set up. But I do think there will be a large complex of storms that will modulate the northern extent. Where does that set up? I don’t think we have an idea of that now. An evolution like Easter 2020 is possible but maybe shifted NW a bit.

 

[warneagle]

Completely different set up. But I do think there will be a large complex of storms that will modulate the northern extent. Where does that set up? I don’t think we have an idea of that now. An evolution like Easter 2020 is possible but maybe shifted NW a bit.

Yeah I could see a scenario where the convection lingers around and the best parameters are confined south of I-20 for most of the day. Obviously still a lot of disagreement between the models on the exact northern extent of the threat and we won't really know until the morning of. Easter 2020 could end up being an apt analogy.

 

[Fred Gossage]

Yeah I could see a scenario where the convection lingers around and the best parameters are confined south of I-20 for most of the day. Obviously still a lot of disagreement between the models on the exact northern extent of the threat and we won't really know until the morning of. Easter 2020 could end up being an apt analogy.

The GFS is the most truncated with its warm sector out of all the models, is suffering from convective feedback that Helen Keller could see, and it still gets the warm sector north of the AL/TN line. Some of you guys are in for a surprise...

 

[Fred Gossage]

This, alone, tells you that the operational GFS is suffering from convective feedback. This is the MSLP spread from all the GFS ensemble members. Note the clustering back near Paducah and all the members near or below 990mb.

 

[Fred Gossage]

The thing that may hang this up is if the morning storms in MS/AL keep developing on themselves during the day instead of shifting northeastward with time. There's no wedge this time. And there's a 65-70 kt LLJ behind the storms to help promote RAPID air mass recovery if the storms do move out of the way during the day. (Think of how fast the air mass recovered across Alabama behind the morning QLCS on 4/27/11 or how fast the dewpoints rose through central AL on Easter of last year, THAT kind of rapid recovery). We just need to make sure the storms shift northeastward with time instead of sitting there and backbuilding on themselves. They SHOULD move out with time, given the strong wind fields and steeper lapse rates spreading in with time (which is a sign of synoptic scale capping, even if the models at face value don't show a cap on the soundings, think back to last week over LA/MS where the morning cap was stronger than expected on the soundings).

 

[Fred Gossage]

That's a west central MS sounding under this EML:


Let's be careful with assessing the EML at face value on some of these models that have a decades-long historical bias of underplaying lapse rates and cap strength, shall we...

 

[HazardousWx]

The thing that may hang this up is if the morning storms in MS/AL keep developing on themselves during the day instead of shifting northeastward with time. There's no wedge this time. And there's a 65-70 kt LLJ behind the storms to help promote RAPID air mass recovery if the storms do move out of the way during the day. (Think of how fast the air mass recovered across Alabama behind the morning QLCS on 4/27/11 or how fast the dewpoints rose through central AL on Easter of last year, THAT kind of rapid recovery). We just need to make sure the storms shift northeastward with time instead of sitting there and backbuilding on themselves. They SHOULD move out with time, given the strong wind fields and steeper lapse rates spreading in with time (which is a sign of synoptic scale capping, even if the models at face value don't show a cap on the soundings, think back to last week over LA/MS where the morning cap was stronger than expected on the soundings).

Yeah...a general rule of thumb from 20 years of experience doing this job is that when there are a lot of storms south of us or it rains a lot in the morning here, we don't get much. We sent out posts on our department pages, did media interviews and ran all equipment through checks and fielded what seemed like hundreds of calls last week and we got no severe, but rather flash flooding. Now, they are saying we could have flooding again.

 

[Fred Gossage]

Yeah...a general rule of thumb from 20 years of experience doing this job is that when there are a lot of storms south of us or it rains a lot in the morning here, we don't get much. We sent out posts on our department pages, did media interviews and ran all equipment through checks and fielded what seemed like hundreds of calls last week and we got no severe, but rather flash flooding. Now, they are saying we could have flooding again.

But when that general rule fails, it fails in a horrible way. This isn't like last week. There's no wedge in place, and the low-level jet is literally double the intensity it was over north Alabama last Wednesday afternoon. That makes all the difference in the world.

 

[HazardousWx]

But when that general rule fails, it fails in a horrible way. This isn't like last week. There's no wedge in place, and the low-level jet is literally double the intensity it was over north Alabama last Wednesday afternoon. That makes all the difference in the world.

You can bet I'm keeping an eye on it. It was the first thing I checked when I woke up this morning.

 

[Clancy]

For those of us in Georgia, don't sleep on this one just because you got rain and rumbles of thunder the last time.

 

[Fred Gossage]

For those of us in Georgia, don't sleep on this one just because you got rain and rumbles of thunder the last time.

Exactly. No big wedge this time, and a much stronger low-level jet the whole day. Air mass recovery will be easier this go around.

 

[Fred Gossage]

A couple of things stand out to me...

1. The HRRR is not segmented and broken apart with the main trough like the NAM and GFS. It is consolidated into one major shortwave, similar to the Euro, UKMET, and Canadian.

2. What may be more important, notice the lead shortwave over middle TN and north AL at 12z Thursday. It is already there and is moving northeast out of the area. Immediately behind it, there is subsidence aloft and mesoscale shortwave ridging. This also coincides with a strengthening EML moving in from the southwest with Oklahoma loaded gun type capped soundings through central Mississippi.

 

[CheeselandSkies]

Man, run after run the NAM soundings just keeps popping analogs from the 5/2003 outbreak sequence, particularly the 4th (most prolific/violent day of the sequence), but also the 10th (last day of the sequence, also a high risk which produced numerous strong tornadoes, although none officially violent). And per what's been posted above, it's one of the more subdued solutions.

 

[MattW]

For those of us in Georgia, don't sleep on this one just because you got rain and rumbles of thunder the last time.

How do you get to these on the CIPS site?

 

[Clancy]

How do you get to these on the CIPS site?

I'm away from my computer at the moment but when I get back I'll edit this post to add a link.

Edit: Link here http://www.eas.slu.edu/CIPS/MODEL/WXmodel.php