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Severe Weather 2025

Fred Gossage said:
Even with a little more space between the two waves from the main one potentially slowing down a little, we still have a situation where the lead wave that we were looking to lift out to act as a primer not only slides across instead, but it tries to dig and amplify after it gets out into the western Atlantic. That will also mess up the wavelengths and moisture return/quality, regardless of the timing of the main wave behind it. If the lead wave isn't lifting in latitude as it comes across the eastern United States and flattening and shearing out as it does, there is a legitimate reason why those models are lacking in moisture, even if the timing of the wave behind it is getting slightly delayed.
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Everything just too darn amplified on the 12Z GFS. This is what I was talking about some days ago about wavelength (E-W) being equally if not more important than amplitude (N-S).

The only good thing about that run from my Midwest chaser perspective is that it does leave just enough moisture for a potential cold core setup somewhere in Illinois that would fall on a Saturday. Throw out overall MLCAPE, 3CAPE is what's important here and 62/54 is a doable LCL and with decent depth to about 850mb.

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tennessee storm chaser said:
Think the super cold weather we had this winter and the snow along the gulf earlier has tampered things bit. May take while to recover from that
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Areas as far north as Nashville have already hit 80 for the year, and the whole winter, Gulf sea surface temperature anomalies were above where they were in early 2011. No sir, that's not what is going on, and that's not how it works. This comes down to trough/ridge positioning and amplitude across the CONUS into the western North Atlantic and how that dictates whether or not we are drawing north quality moisture as systems come out. Until about early-mid May, you're always looking for low-level moisture originally coming from the Caribbean. Gulf SSTs have zero effect on that.
 
I will caution that this isn't necessarily "over" yet. The 12z Euro ensemble mean never turns sfc/low-level winds away from being southerly the whole time between the lead midweek shortwave and the main ejecting late week trough. That would mean the Euro ensembles do not scour the Gulf moisture, and a significant number of ensemble members bring substantial CAPE (1000-2000 j/kg or higher in some cases) well inland across the Southeast with the main wave. Just the large changes in synoptic trough evolution with the main system between today's 12z Euro and 00z Euro last night make it overwhelmingly apparent that we don't have synoptic trough geometry with the main wave tacked down yet. If the Euro ensembles are closer to correct about us not sending a front south into the Gulf, we need to watch trough geometry with the main system carefully. Those waves are often more amplified this far out than they end up being in reality. I think we should be a wait-and-see type holding pattern the next couple/few days to watch how data evolves. While this setup does have significant hurdles to clear, there is still believable data (and more than just a little) that shows them getting cleared. It's not time to let our guard down on a potential significant threat just yet... it's just also not remotely close to time to push forward with the idea of one either.

EDIT: The GFS ensembles aren't on-board with the Gulf scouring idea either. It seems both ensemble sets want to hang up the sfc/low-level front from the lead system near the coastline, which is plenty close enough to get it well back north with the main wave as long as the main wave isn't too amplified and induces a significant easterly component to the low-level flow.
 
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To go along with the previous post of mine, there is still a fairly robust (by March standards in Dixie Alley, for sure) signal for instability well inland across MS/AL/TN and adjacent areas with the lead wave. That tells me the Euro ensembles do not agree with the Gulf scouring solution.
 
I'm just sitting back and drinking my coffee. I'll add my take on here when we get closer. However, CPC seems to agree with late next week thru next weekend for potential trouble. I'm fixing to do a Patreon post and text my EMA director about it.
 

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JPWX said:
I'm just sitting back and drinking my coffee. I'll add my take on here when we get closer. However, CPC seems to agree with late next week thru next weekend for potential trouble. I'm fixing to do a Patreon post and text my EMA director about it.
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Fwiw, CIPS is still very much picking up on this event, moisture and troughing woes notwithstanding.
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Fred Gossage said:
*PICS REMOVED FOR BREVITY*

To go along with the previous post of mine, there is still a fairly robust (by March standards in Dixie Alley, for sure) signal for instability well inland across MS/AL/TN and adjacent areas with the lead wave. That tells me the Euro ensembles do not agree with the Gulf scouring solution.
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What’s the vertical scale on the left side of those pics? I understand the rest of those images.
 
We're at the stage out in time with pretty much all the models where they usually like to show everything but the truth when it comes to trough geometry... but even the ensembles are leaning more toward the idea of the operational models where the lead jet energy in the Friday/Saturday trough gets pulled north, and it stretches the trough and the base of it waits until Saturday afternoon/night to swing across. Interestingly, while that would decrease the chances of a major outbreak if it were to happen, it would actually probably increase the chances of there being a tornado event actually verifying instead of the wave being a complete dud, because then the lead impulse acts as the primer wave, and you get a full day of then absolutely guaranteed return flow regardless of what the ridge and wavelengths are doing out in the Atlantic to the east. The trough geometry isn't optimal, but you still get a low-level air mass supportive of severe weather with low-level and deep-layer wind fields supportive of some caliber of a tornado threat (linear, cellular, or mixed would be tbd). It just wouldn't be the headliner national-news-story type event this was trying to present itself as at one point. The main surface low positioning would still be well north, but as long as you're still getting pressure falls to back the low-level winds ahead of the front and height falls aloft, that doesn't matter. With the 11/10/2002 tornado outbreak, the main surface low was moving into southern Canada and away from the outbreak area that morning. In the 3/3/1966 "Candlestick Park" F5 event near Jackson, MS, the synoptic surface low was in central South Dakota. It's actually the same low pressure that caused the big Fargo, ND blizzard that led to the infamous photo of the guy standing on the snow drift that came up to the top of telegraph poles. Surface low position doesn't matter if you still have a catalyst to have pressure falls and back low-level winds ahead of the front and you still have large scale ascent aloft.

But we're now in that funky 4-7 day window where both operational models and ensembles sometimes do all kinds of funky things with trough evolution and geometry before settling onto what will be reality about the 3-4 day timeframe. A lot of people don't remember this because it was touted as a significant severe weather threat in general from a week out, but the models did not show a trough geometry favorable for a discrete supercell swarm with 4/27/11 until about the 00z model cycle the night the Day 3 MDT was issued. You can go back and look, and it was even talked about in real time in the medium range days prior in that thread. The trough geometry was more disjointed and meridional and supported something more along the lines of a repeat of April 4th but with more tornadoes. It wasn't until the 00z model cycle leading into the Day 3 MDT issuance that we suddenly had a shift toward a broad-based low amplitude trough geometry. Now, that is NOT being said to make even the absolute slightest comparison between that threat and this potential one, but I'm saying that to show the point that, even with slam dunk home run type setups like that, the global models and even their ensembles still do funky things with trough evolution and geometry in the medium range. The main takeaway from that message is: there's still a lot we just don't know yet, and even if what we're currently being presented ends up being reality, we don't have a way of having confidence in that yet.
 
Ok, 06Z GFS, I see you...

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A southwesterly component to the flow in that exit region coupled with at least mid-50s dewpoints is what I need for a regional chase opportunity next Friday. As Fred has pointed out, trough orientation and consequent degree of supercell tornado threat will continue to bounce around on the models. This has implications on both potential for moisture return and degree of forcing, and how well that forcing is co-located with the unstable warm sector.
 
Well that 06z GFS run certainly didn't seem to care that the lead wave dove through the SE. That main trough is nuts, 135 kt 500 mb jet and a 969 mb low.
 
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