April 6-10th Severe Potential

[andyhb]

There's been a clear and steady slowing trend with the progression of the upper trough, though, from the 12z run this morning to tonight's 00z run. Whether it means anything, being the NAM beyond H+48 and a synoptic-scale feature upstream of the CONUS, is questionable. But I'm nervously keeping an eye on whether that trend occurs with the GFS or Euro.

 

See, the thing is (obviously looking beyond whatever favorable range the NAM has), with how weak the cap is even until 00z (seeing soundings even down at Lawton with -25 J/kg CIN at that time), you would probably need less forcing to break it with this verbatim.

[Thundersnow12]

There's been a clear and steady slowing trend with the progression of the upper trough, though, from the 12z run this morning to tonight's 00z run. Whether it means anything, being the NAM beyond H+48 and a synoptic-scale feature upstream of the CONUS, is questionable. But I'm nervously keeping an eye on whether that trend occurs with the GFS or Euro.

 

I will say that the lack of explicit QPF on the NAM down the dryline doesn't bother me at this stage, given the BMJ convective scheme is known to struggle in this scenario. If anyone gets nervous about that, just know that it showed a cap bust along the length of the dryline the night before this.

 

I was just going to say this before I got to the sentence.

 

I believe for days it was showing a cap bust or barely any precip breaking out, yet storms were already ongoing by like noon or 1pm across KS. 

[Jim Marusak]

How so?

 

Everything I'm seeing is indicating that Wednesday will be driven heavily by the synoptic side, particularly the timing of the synoptic scale trough.

when it comes to forcing, you're going to have the trough come out of the rockies. but if the models are close, the complete trough isn't across until you're between 00z and 03z. so to get things going anywhere before 00z, you're going to be leaning more on drylines, the i-29 inverse trough, and other means. That being said, whatever gets ignited before 00z, esp in KS, MO, and eastern NE, is going to get ugly and fast with fairly high mesoscale mechanical and thermal dynamics.

 

Once you get past 03Z, if the NAM and such are close, then the 500 and 700 low are across, with all the vorticity and lift that comes with them, and they take over and gathers whatever is out there into a massive linear outbreak where anything separating from the line will go tornadic and those that do stay in line are more gusts and hail.

 

Bring that 500 and 700 trough to the lee side of the rockies 3-6 hours earlier, and god help anyone in KS/OK/NE/IA/MO as everything will be in place at the right time. and given we're still 60 hours out, a lot of time to speed things up enough to make that happen. not saying the latest model trends favor that  though,as  they do slow things a bit.

[andyhb]

00z GFS continues to look a tad faster with the dryline mixed to I-35 at 00z Thursday. Still impressive all around though with excellent cross-overs and strong deep layer shear across the dryline.

[ZackH]

00z GFS looks better than the 18z run IMO... Still just wish the dry line was further west. I'm not as worried about the NAM slow down as I was personally. Both models are showing that very solid piece of energy still arriving as early as 21z and I didn't really see the NAM slowing from the 18z to 00z runs. A compromise between GFS and NAM would be ideal.

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[brettjrob]

The GFS is almost always going to depict the dryline too far E in these setups (same deal with the SREF, as we start looking at that more). Still, I'd like substantially more buffer room between initiation and I-35 hell, considering supercell maturity would probably be reached 30-50 mi. off the dryline. With any luck, the dryline will be within a county either side of the TX/OK border at initiation, at least down south.

 

Now, the dryline orientation on tonight's GFS is slightly concerning. But no point getting bogged down in those details until tomorrow evening at the earliest.

[thewxmann]

0Z Euro lights up the entire dryline from srn KS to west TX on Wed.

 

EDIT: also quite a bit flatter/lower amplitude with the parent trough.

[andyhb]

0Z Euro lights up the entire dryline from srn KS to west TX on Wed.

 

EDIT: also quite a bit flatter/lower amplitude with the parent trough.

 

Frankly this lower amplitude (but still plenty strong) solution is almost your ideal look, so that you have enough forcing spread east for initiation along most of the dryline, yet you don't have everything going nuts at once ala 5/24/11 and relatively quickly going linear. Also, aside from any currently unforeseen weaknesses at H7/etc, there are really no weakness in the wind profiles along the entire dryline with rapid veering to west-southwesterly flow above 850 mb and significantly backed flow below it.

[andyhb]

Seeing a couple more caveats for Wednesday with the 12z NAM/GFS solutions, with some questions in moisture depth given the relatively low PWAT values over the Gulf currently. The good thing I do see in this is all along on the models, the main source region for the deep moisture seems to actually be somewhat inland over Mexico, with moisture from the Caribbean penetrating west given the background flow. There are currently 12-14˚C H85 Tds over this area northward into Central Texas.

 

Secondly, there appears to be a bit of an S-shaped hodograph showing up with slight backing at/above 500 mb. One positive, if there is one, is that it isn't lower towards the ground. This showing up in the 700 mb level can ruin setups pretty fast. Also, it currently is fairly minor, but this needs to be monitored closely.

 

I'll also mention that the LLJ seems to be taking on a bit more of a SSW orientation.

[brettjrob]

Seeing a couple more caveats for Wednesday with the 12z NAM/GFS solutions, with some questions in moisture depth given the relatively low PWAT values over the Gulf currently. The good thing I do see in this is all along on the models, the main source region for the deep moisture seems to actually be somewhat inland over Mexico, with moisture from the Caribbean penetrating west given the background flow. There are currently 12-14˚C H85 Tds over this area northward into Central Texas.

 

Secondly, there appears to be a bit of an S-shaped hodograph showing up with slight backing at/above 500 mb. One positive, if there is one, is that it isn't lower towards the ground. This showing up in the 700 mb level can ruin setups pretty fast. Also, it currently is fairly minor, but this needs to be monitored closely.

 

I'll also mention that the LLJ seems to be taking on a bit more of a SSW orientation.

 

Agreed on all counts. I'd argue all these issues are manifestations of the increasingly junky, sheared-out upper trough. It's no coincidence that Wednesday looked apocalyptic 36-48 h ago on the same runs that also ejected a negative-tilt closed low with a compact vort max on Thursday. I swear, rapid model trends in that 3-5 day range almost always come back to bite you in the end.

 

Pretty sure the last high-caliber setup with a truly negative-tilt trough, favorably-oriented dryline, and backed low-levels was the Rozel day in 2013. Pathetic.

[andyhb]

Agreed on all counts. I'd argue all these issues are manifestations of the increasingly junky, sheared-out upper trough. It's no coincidence that Wednesday looked apocalyptic 36-48 h ago on the same runs that also ejected a negative-tilt closed low with a compact vort max on Thursday. I swear, rapid model trends in that 3-5 day range almost always come back to bite you in the end.

 

The 12z GFS still does this.

[brettjrob]

The 12z GFS still does this.

 

Eh, not seeing a closed low by 00z Fri using 60 m contours. Regardless, the trend is clearly for the energy to lose its coherence as it phases with northern stream crap.

 

12z today vs. 12z yesterday vs. 12z Sat

 

Not to say it's impossible for that trend to reverse, since obviously most of the upper energy is still offshore.

[thewxmann]

Seeing a couple more caveats for Wednesday with the 12z NAM/GFS solutions, with some questions in moisture depth given the relatively low PWAT values over the Gulf currently. The good thing I do see in this is all along on the models, the main source region for the deep moisture seems to actually be somewhat inland over Mexico, with moisture from the Caribbean penetrating west given the background flow. There are currently 12-14˚C H85 Tds over this area northward into Central Texas.

 

Secondly, there appears to be a bit of an S-shaped hodograph showing up with slight backing at/above 500 mb. One positive, if there is one, is that it isn't lower towards the ground. This showing up in the 700 mb level can ruin setups pretty fast. Also, it currently is fairly minor, but this needs to be monitored closely.

 

I'll also mention that the LLJ seems to be taking on a bit more of a SSW orientation.

 

The Euro has always been more bearish about low-level moisture... so no surprise there. LCL's will be a problem before 0Z, no doubt about it. The veered LLJ will not help in that regard.

[andyhb]

The Euro has always been more bearish about low-level moisture... so no surprise there. LCL's will be a problem before 0Z, no doubt about it. The veered LLJ will not help in that regard.

 

See, the thing is that the Euro also appears to be quite low with moisture near the surface as well. Whether it is picking up stronger mixing than the other guidance or not, I'm wondering whether it's going to be low with the moisture and the other two models are going to be a bit high, perhaps settling with something in between is best.

 

Through Thursday, the Euro has been fluctuating rather wildly run to run.

[thewxmann]

See, the thing is that the Euro also appears to be quite low with moisture near the surface as well. Whether it is picking up stronger mixing than the other guidance or not, I'm wondering whether it's going to be low with the moisture and the other two models are going to be a bit high, perhaps settling with something in between is best.

 

Through Thursday, the Euro has been fluctuating rather wildly run to run.

 

Idk, I don't think it's been wildly fluctuating that much... the trend of a flatter, more sheared out trough is evident. 

[andyhb]

Idk, I don't think it's been wildly fluctuating that much... the trend of a flatter, more sheared out trough is evident. 

 

Key words being through Thursday...

[ZackH]

I'm still seeing the potential for a few nice tornadoes on Wednesday... The 12z Euro was pretty potent. Maybe not an outbreak but I just want a tornado and I think the ceiling is still quite nice.

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[TropicalAnalystwx13]

The 12z ECMWF has 0-3km SRH near 600m2/s2 near the central Kansas-Oklahoma border by 0z Thursday. Assuming we see at least some initiation, which I think we will, I wouldn't be surprised if a significant or even violent tornado was put down. Still a good amount of time for models to change around.

[SmokeEater]

Was thinking very, very hard about driving to Norman tonight to chase with David on Wednesday. Maybe I'm better off waiting for a better, more multiple day event, even though I would probably see my first real supercell and possibly tornado on Wednesday. If I did it now, I wouldn't be able to do anything else this season.

[Chicago Storm]

Was thinking very, very hard about driving to Norman tonight to chase with David on Wednesday. Maybe I'm better off waiting for a better, more multiple day event, even though I would probably see my first real supercell and possibly tornado on Wednesday. If I did it now, I wouldn't be able to do anything else this season.

I wouldn't do it.

I'd wait for a better looking and/or a multiple day event.

[brettjrob]

I wouldn't do it.

I'd wait for a better looking and/or a multiple day event.

 

Strongly agree.

 

I'll go a step further: anyone who's in a one-and-done chase/chasecation situation living on the coasts should never consider blowing it on anything before May 1. And most of the time, more like May 15. I can't even begin to describe or list all the reasons why the average chase day between 15 May-30 June is many times more enjoyable than the average one in March or April.

[Ian]

Strongly agree.

 

I'll go a step further: anyone who's in a one-and-done chase/chasecation situation living on the coasts should never consider blowing it on anything before May 1. And most of the time, more like May 15. I can't even begin to describe or list all the reasons why the average chase day between 15 May-30 June is many times more enjoyable than the average one in March or April.

I'd probably never go early May again as a 2 week stint after 2011. Mid-May to Mid-June is where it's at unless you are spot chasing a giant setup. But of course it's early.. people seem eager to rush out from great distance to the first event these days for some reason. If I had the money to just go on a whim I wouldn't turn down an April 2012 or something.

[LocoAko]

I wouldn't do it.

I'd wait for a better looking and/or a multiple day event.

 

Thirded.

[Minnesota Meso]

Strongly agree.

 

I'll go a step further: anyone who's in a one-and-done chase/chasecation situation living on the coasts should never consider blowing it on anything before May 1. And most of the time, more like May 15. I can't even begin to describe or list all the reasons why the average chase day between 15 May-30 June is many times more enjoyable than the average one in March or April.

 

I wouldn't do it either, se Kansas looks good Wednesday night, but its very local IMO.  Thursday in my mind is not what many are saying, I think convection just ahead of the warm front or along it may lock the best cape values around the AR/LA/Tex area.  This seems to be reflected by the ECMWF.

[andyhb]

I wouldn't do it either, se Kansas looks good Wednesday night, but its very local IMO.  Thursday in my mind is not what many are saying, I think convection just ahead of the warm front or along it may lock the best cape values around the AR/LA/Tex area.  This seems to be reflected by the ECMWF.

 

If you're restricting your analysis to the Euro, it looks better over a larger area than the GFS or NAM for Wednesday.

[Quincy]

I'd probably never go early May again as a 2 week stint after 2011. Mid-May to Mid-June is where it's at unless you are spot chasing a giant setup. But of course it's early.. people seem eager to rush out from great distance to the first event these days for some reason. If I had the money to just go on a whim I wouldn't turn down an April 2012 or something.

As far as big tornado days in good chasing territory, late May to mid-June has been the sweet spot over the past ten years. Last year, the best stretch was rather late, June 16-18. The image below focuses on the top tornado days across the Plains/High Plains/Iowa. Early season events do happen, but haven't been very common.

[Amped]

As far as big tornado days in good chasing territory, late May to mid-June has been the sweet spot over the past ten years. Last year, the best stretch was rather late, June 16-18. The image below focuses on the top tornado days across the Plains/High Plains/Iowa. Early season events do happen, but haven't been very common.

image.jpg

 

Late May and June is definitely better on the plains.  Arkansas seems like it has a habit of getting hit in late March and April.

[Quincy]

Late May and June is definitely better on the plains. Arkansas seems like it has a habit of getting hit in late March and April.

Some of the biggest outbreaks have been in April, but in Dixie Alley. Not too friendly for chasing.

[jojo762]

As far as big tornado days in good chasing territory, late May to mid-June has been the sweet spot over the past ten years. Last year, the best stretch was rather late, June 16-18. The image below focuses on the top tornado days across the Plains/High Plains/Iowa. Early season events do happen, but haven't been very common.

image.jpg

just wonder, but does anyone know what the day in late December was??? Especially over the plains; I don't remember a big tornado day in December ever in the plains...

[brettjrob]

just wonder, but does anyone know what the day in late December was??? Especially over the plains; I don't remember a big tornado day in December ever in the plains...

 

It's late November, and I'm going to guess 11/27/05. Lots of reports across E KS but nothing too significant (bordering on a cold-core setup). There's no way that's in the top 13 days for Plains tornado reports for the past decade, but if Quincy meant the top day each individual year, I suppose it's possible that had more reports than any other day in 2005 (fairly quiet spring in the Plains).