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Severe WX Severe Threat 17-18 March 2021

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I'm not really sure how climate change applies to this particular event-based thread. It most certainly shouldn't be used as reasoning when formulating a forecast or expectations for this event.
Think he was referring to overall , climate change seems to increase the violent tornado activity last couple decades or so... wasn’t referring to this particular threat pretty sure .
 

Matt Grantham

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Think he was referring to overall , climate change seems to increase the violent tornado activity last couple decades or so... wasn’t referring to this particular threat pretty sure .

I was referring to the quote below. No idea what that has to do with this event or what even prompted it. It can be interpreted as downplaying this event.

" I think that the overall warming of the Pacific basin over the past decade, coupled with recent -AMO trends (weakening AMOC) in the North Atlantic, has made low-amplitude, progressive patterns less likely, even during -ENSO/-PDO setups, hence the dearth of major, widespread tornado outbreaks, for the most part, since 2011–12, especially over the Plains. So events like Palm Sunday 1920/‘65, Super Outbreaks ‘74/‘11, Super Tuesday ‘08, et al. will be harder to come by for the most part, due to AGW being reflected in the absorption of heat and fresh water by the major ocean basins, especially the Pacific and the North Atlantic."
 

Fred Gossage

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Expect a trend toward a stronger low-level jet as we get closer. This is part of that isallobaric response I've talked about that the GFS and NAM have issues with, and it's been a long-standing issue for more than a decade. But even the 00z NAM tonight, which can often struggle to close off a surface low 72-84 hrs out, has a 993mb sfc low at 12z Wednesday and a much more organized 850-925mb jet response. Matt and I have been looking at other synoptic analogs that had an almost identical 850mb cyclone structure and height gradient structure in the warm sector to what is modeled, and all of them had a 50-60 kt 850mb jet. Even the GFS ensembles continue to significantly intensify 850mb winds over the warm sector with each run as we get closer. The NAM, which struggles with the same issues as the GFS, also has a solid backing of the surface winds through the whole warm sector of SE to SSE versus the due S on the GFS on Wednesday morning. The fact that the NAM often struggles with the same issues but has a much stronger low-level jet response and backed low-level winds tells me everything I need to know.
 

Richardjacks

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Expect a trend toward a stronger low-level jet as we get closer. This is part of that isallobaric response I've talked about that the GFS and NAM have issues with, and it's been a long-standing issue for more than a decade. But even the 00z NAM tonight, which can often struggle to close off a surface low 72-84 hrs out, has a 993mb sfc low at 12z Wednesday and a much more organized 850-925mb jet response. Matt and I have been looking at other synoptic analogs that had an almost identical 850mb cyclone structure and height gradient structure in the warm sector to what is modeled, and all of them had a 50-60 kt 850mb jet. Even the GFS ensembles continue to significantly intensify 850mb winds over the warm sector with each run as we get closer. The NAM, which struggles with the same issues as the GFS, also has a solid backing of the surface winds through the whole warm sector of SE to SSE versus the due S on the GFS on Wednesday morning. The fact that the NAM often struggles with the same issues but has a much stronger low-level jet response and backed low-level winds tells me everything I need to know.
When I looked at everything today, I kept thinking to myself the winds will likely be stronger as we have see the models catchup.

I would think the primary storm mode will be supercells, plenty of shear just not sure about spacing/capping
 

Fred Gossage

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That's a big-league EML that will be just to our southwest Wednesday morning. There's no reason for it to just vanish. The EML often trends more significantly with these systems as we get closer. We're in a background state that favors large-scale EML advection. I expect a somewhat stronger cap in the morning. There have been many of these events where the forecast soundings have shown the warm sector completely uncapped in the morning until we get within a day or two of the event. Just stepping back away from the face value stuff and looking at the mid-level source regions and the trajectories involved, there should be a synoptic-scale cap that spreads in behind the warm front.
 

Richardjacks

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Expect a trend toward a stronger low-level jet as we get closer. This is part of that isallobaric response I've talked about that the GFS and NAM have issues with, and it's been a long-standing issue for more than a decade. But even the 00z NAM tonight, which can often struggle to close off a surface low 72-84 hrs out, has a

That's a big-league EML that will be just to our southwest Wednesday morning. There's no reason for it to just vanish. The EML often trends more significantly with these systems as we get closer. We're in a background state that favors large-scale EML advection. I expect a somewhat stronger cap in the morning. There have been many of these events where the forecast soundings have shown the warm sector completely uncapped in the morning until we get within a day or two of the event. Just stepping back away from the face value stuff and looking at the mid-level source regions and the trajectories involved, there should be a synoptic-scale cap that spreads in behind the warm front.
 

Fred Gossage

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Both the parallel and operational GFS are now backing the surface winds to due south in the warm sector Wednesday afternoon and keep them do south until the dryline/Pacific front arrives. The parallel GFS is also stronger in the midday and afternoon with the 850mb jet. I think we're starting to see the first signs of things trending toward responding the way they should.
 

Taylor Campbell

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The CIPS analogs are really painting an increasing, dangerous threat at 5 days out.

It rarely if ever ends well when you have this type of wind and thermodynamic field. You’d simply have to completely change it to revert disaster. The charts on the GFS/NAM are as classic as it gets for large tornado outbreaks with that hooking supercell like appearance in trough orientation.
 

Timhsv

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1st PDS sounding I've seen this year across Alabama. Sounding location is near Guin, AL at 18Z Wed. I bet those 0-1km winds will become even more backed as time goes along. This whole setup is becoming ominous at even this point.


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