Severe WX Severe Threat 17-18 March 2021

[Ingyball]

I see that UH tracks have been the talk this morning. This is a great Twitter thread on why you need to be careful when using UH tracks, especially in the presents of a limited amount of tracks.



The CAM's already have a significant amount of UH tracks on Wednesday and they still may be underestimating them for smaller storms.

 

[maroonedinhsv]

I agree. I have this website i use thats called severeweatheroutlook.com it has its accurate forecasts and updates if anything changes. it doesn’t require social media and it’s way easier! hope it helps!

I may have missed something as I quickly perused it, but that website appears to simply take images from the Storm Prediction Center and repost them - you'd be better off just going to the SPC site in the first place.

 

[MNTornadoGuy]

Gyazo Screen Video

gyazo.com

There is a lot of model disagreement at 0Z.

 

[Fred Gossage]

Interesting trend on the nam....
Fred, do you think the wedge will be this strong in NE Alabama?

I'm not sure yet. I'm not sure I believe a HSV dewpoint well down into the 50s though. Especially if the morning stuff isn't as widespread (and it has less of a forcing mechanism in the morning the less the LLJ is across the front), then the less likely that is to happen.

 

[Richardjacks]

I'm not sure yet. I'm not sure I believe a HSV dewpoint well down into the 50s though. Especially if the morning stuff isn't as widespread (and it has less of a forcing mechanism in the morning the less the LLJ is across the front), then the less likely that is to happen.

That's what I am thinking too, I remember the days when ETA would underforecast a wedge, now I am wondering if it is the opposite.

 

[speedbump305]

I may have missed something as I quickly perused it, but that website appears to simply take images from the Storm Prediction Center and repost them - you'd be better off just going to the SPC site in the first place.

Yeah. I use both because sometimes i can’t find the SPC outlook. So if i can’t the original spc outlook, i use the severe weather outlook website

 

[andyhb]

12z NAM has a weaker LLJ by 00z than previously. With that said, the backed surface flow it shows in MS will yield tornadoes with any supercells there.

 

[maroonedinhsv]

Yeah. I use both because sometimes i can’t find the SPC outlook. So if i can’t the original spc outlook, i use the severe weather outlook website

Always look here:

Storm Prediction Center Convective Outlooks

Severe weather, tornado, thunderstorm, fire weather, storm report, tornado watch, severe thunderstorm watch, mesoscale discussion, convective outlook products from the Storm Prediction Center.

www.spc.noaa.gov

 

[speedbump305]

Always look here:

Storm Prediction Center Convective Outlooks

Severe weather, tornado, thunderstorm, fire weather, storm report, tornado watch, severe thunderstorm watch, mesoscale discussion, convective outlook products from the Storm Prediction Center.

www.spc.noaa.gov

Thank you!

 

[cmking64]

12z NAM has a weaker LLJ by 00z than previously. With that said, the backed surface flow it shows in MS will yield tornadoes with any supercells there.

Long time lurker, first time post. This is currently my greatest concern with Wednesday's setup. The LLJ doesn't maximize until closer to 0z with storms already ongoing in the warm sector. The most significant tornado threat would likely come with the final wave of discrete to semi discrete storms along the front in that scenario rather than the open warm sector cells during the afternoon hours.

 

[Casuarina Head]

12z NAM has a weaker LLJ by 00z than previously. With that said, the backed surface flow it shows in MS will yield tornadoes with any supercells there.

Along with the CAD, this likely will reduce the ceiling for several violent tornadoes somewhat, though I still expect at least one EF4+ event, given other parameters. I have strong doubts that there will be more than two EF4+ events, however, given that thermodynamics and shear were more favourable during the overnight phase of the Super Tuesday outbreak (2008), which produced four of its five EF4s after sunset, if I recall correctly. Most of the significant tornadoes look to occur in association with the “final wave” of cells, so most of these are likely to be EF2–3, with one (maybe two) EF4. I would compare this event to 04/28/2014.

 

[andyhb]

Along with the CAD, this likely will reduce the ceiling for several violent tornadoes somewhat, though I still expect at least one EF4+ event, given other parameters. I have strong doubts that there will be more than two EF4+ events, however, given that thermodynamics and shear were more favourable during the overnight phase of the Super Tuesday outbreak (2008), which produced four of its five EF4s after sunset, if I recall correctly. Most of the significant tornadoes look to occur in association with the “final wave” of cells, so most of these are likely to be EF2–3, with one (maybe two) EF4. I would compare this event to 04/28/2014.

I think it's way too early to be making specific calls like this.

 

[GA Stormchaser]

Along with the CAD, this likely will reduce the ceiling for several violent tornadoes somewhat, though I still expect at least one EF4+ event, given other parameters. I have strong doubts that there will be more than two EF4+ events, however, given that thermodynamics and shear were more favourable during the overnight phase of the Super Tuesday outbreak (2008), which produced four of its five EF4s after sunset, if I recall correctly. Most of the significant tornadoes look to occur in association with the “final wave” of cells, so most of these are likely to be EF2–3, with one (maybe two) EF4. I would compare this event to 04/28/2014.

What model are you looking at, that shows specific number of tornadoes by EF rating? I was under the impression that EF ratings could only be determined after the event, by inspecting the damage.


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[Kory]

No change on the 12z GFS. I’ll be interested to see if the NAM is a blip or not.

 

[Casuarina Head]

I think it's way too early to be making specific calls like this.

So do you think that the potential is still there for this event to surpass 04/28/2014 in terms of EF4+ tornadoes?

What model are you looking at, that shows specific number of tornadoes by EF rating? I was under the impression that EF ratings could only be determined after the event, by inspecting the damage.

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I was looking at the number of high-end UH tracks indicating large, robust circulations. The more of these, the more favourable the environment.

Certainly, resolution is a big problem, so smaller circulations could still be violent, but the number of big ones says something about conditions.

I’m certainly not downplaying the potential of this event, by any stretch, especially given the overnight timing, which could prove deadly.

 

[Kory]

Add in the 06z Euro continuing to show a notable threat deep into MS/AL and into the night. It seems that around sundown is when the low level shear really kicks up.

 

[Brice Wood]

So do you think that the potential is still there for this event to surpass 04/28/2014 in terms of EF4+ tornadoes?

I was looking at the number of high-end UH tracks indicating large, robust circulations. The more of these, the more favourable the environment.

Certainly, resolution is a big problem, so smaller circulations could still be violent, but the number of big ones says something about conditions.

I’m certainly not downplaying the potential of this event, by any stretch, especially given the overnight timing, which could prove deadly.

So are you saying these storms are going to be less surface-based than the ones we had this past outbreak?

 

[Snowyfbaby]

So do you think that the potential is still there for this event to surpass 04/28/2014 in terms of EF4+ tornadoes?

I was looking at the number of high-end UH tracks indicating large, robust circulations. The more of these, the more favourable the environment.

Certainly, resolution is a big problem, so smaller circulations could still be violent, but the number of big ones says something about conditions.

I’m certainly not downplaying the potential of this event, by any stretch, especially given the overnight timing, which could prove deadly.

You are wrong and I would expect to have an ef5.

 

[Bama Ravens]

So do you think that the potential is still there for this event to surpass 04/28/2014 in terms of EF4+ tornadoes?

I don’t think there is anyway to answer that. We know that tomorrow will likely have storms that can produce tornadoes, some of which may be strong, long-track tornadoes. We won’t know how strong any tornadoes that occur tomorrow were until the NWS can survey the damage caused. Like I said, all we know now is that there is a good chance of tornadic storms tomorrow. They might produce EF-4+ tornadoes, they might not. There might be several strong tornadoes, there might just be 1 or 2.

 

[Snowyfbaby]

Ok reset someone give me the latest information and let’s look at the current situation as it plays out now with models and forecasting. Also compare this event to others could this be another April 27th?