2024-04-15 EVENT: NE/KS/OK

[Warren Faidley]

Wise decisions by everyone. If I lived within a few hundred miles, I would go for it, but a long drive or flight from Tucson is not justified. As a long-shot chaser, I might focus a little further south, maybe CDS or even further south / southwest and hope for a cap-cracking, Panahdle magic event near the dryline right before sunset.

Interestingly, the GFS had wonky hodographs for days, not worthy of a "major" event. I figured this would change as the trough approached, but it never did.

There is still plenty of time for things to change. I've seen seesaw patterns like this actully contribute to a bigger day than expected. I believe there will be at least one isolated event, or multiple events after dark.

 

[Mike Smith]

I've taken today's base SPC forecast and modified it a bit: Keep an Eye on the Weather Monday

I can't see that much has changed since Thursday. This morning's FV3 looks almost exactly as I'd pictured it except the storms are just a bit farther southeast ( ~50 mi or so) than I expected.

At 7p Monday, the 3km NAM is showing thunderstorms just starting to fire. At the same time, here are the forecast STP's (middle).

In 2024, the CAMs have generally underforecast moisture but is forecast to be saturated, or nearly so, to 850mb on both the 3kmNAM and FV3 at 00Z along the dry line. Here is the Alva OK 7pm forecast sounding.

 

[Sean Ramsey]

Can't say I'm real encouraged by SPC mentioning initiation after 0z and widespread convection thereafter. Waiting for most of the CAMs to come into range but FV3 is bullish on convection prior to dark, but 3KNAM not so much. One thing I've noticed over the last two seasons is that HRRR tends to be a couple of hours late vs actual initiation so if it doesn't fire storms until 01z it's a fair bet that there will be initiation around 23z.

I'm not much of an night-time chaser so the amount of daylight is important to me. Thankfully, the chances of my target being within two hours drive are pretty good so I'll be out regardless.

 

[Mike Smith]

For what it is worth, sunset at Dodge City Monday is 8:16pm. So, the light should be decent until about 8:30.

 

[Mike Smith]

For those who don't know me, I'm an "old-guy" meteorologist who began forecasting tornadoes in the late 1960's when there were -- gasp -- no models at all . I find that experience very useful as a check for when the models' forecasts look wonky. So, I thought I'd pass along some old time info on the upcoming situation.

The father of severe storms forecasting, the late Col. Bob Miller of the USAF, swore by the SWEAT index which is a really useful product because it combines instability and shear. SWEAT also assumes the moisture reaches 850mb, so it is implicitly saying moisture depth will not have a problem. It predates hodographs by decades. The SWEAT tornado threshold is 500. Below are forecasts from the Saturday 12Z ECMWF (via AccuWeather's model site) and are very high values. Keep in mind Kansas' worst tornadoes (Udall, Greensburg, Ruskin Heights, Topeka, Hesston/Moundridge) were all at or after sunset with the exception of the latter which was afternoon. When the SWEAT is 700+ in a highly dynamic atmosphere (strong PVA plus pressures fall 11mb at DDC in 12hr ending at 7p), a major threat exists.

Miller also had an objective forecast list. Of the first five on his list (in order of importance), all five are "strong" for Monday and, of the next five, all are strong or "moderate."

I agree that this may later in the day than we would like from a chasing/photography point of view. But, from a danger to the public point of view, this could be a bad day. The ECMWF has these 1-hr lightning forecast maps ending at 7p and 11p (WeatherBell). The supercells become more widespread after 11p.

Finally, there is some chance of a warm front play near or north of I-70 in Kansas.

 

[Andy Wehrle]

Agree with the above that Monday is no longer a "drop everything and fly in from halfway cross the country to chase" (if it ever was) type of setup, but is a definite chase if you're local/regional with a high public hazard potential type of setup.

Monday is out of range for me due to work but I plan to chase Tuesday afternoon (have Wednesday morning off, 3AM-noon shift), most likely in Iowa assuming it continues to look at least as good as it does on today's 12Z NAM.

For Monday, the preferred spot could be in south-central Kansas where the 3K NAM appears to portray a dryline bulge with the environment in the attached forecast sounding out ahead of it, but as others have noted, the model has not fired robust supercells in this environment by 0Z Tuesday. However, despite -7 MLCINH, the lack of an apparent warm nose (rightward jog in the temperature profile) on the skew-T suggests to me (someone better versed in thermodynamics and how CINH numbers actually relate to temperatures at certain heights, correct me if I'm wrong) initiation should be commencing shortly if not underway.

As an aside, I threw this together for s***s and giggles and to get pumped for chase season '24 using the music video for Van Halen's "Humans Being" from the Twister soundtrack and my storm footage over the years. Enjoy and here's to successful and safe chasing on Monday/Tuesday!

 

[Rick Schmidt]

I've taken today's base SPC forecast and modified it a bit: Keep an Eye on the Weather Monday

I can't see that much has changed since Thursday. This morning's FV3 looks almost exactly as I'd pictured it except the storms are just a bit farther southeast ( ~50 mi or so) than I expected.

At 7p Monday, the 3km NAM is showing thunderstorms just starting to fire. At the same time, here are the forecast STP's (middle).

In 2024, the CAMs have generally underforecast moisture but is forecast to be saturated, or nearly so, to 850mb on both the 3kmNAM and FV3 at 00Z along the dry line. Here is the Alva OK 7pm forecast sounding.

Mike----One correction, although trivial, Is the 1966 Topeka tornado went all the way through town with the sun up. It occurred roughly from 7:00 to 7:30 on June 8.

 

[JamesCaruso]

For what it is worth, sunset at Dodge City Monday is 8:16pm. So, the light should be decent until about 8:30.

True, but in this situation where it would be an out and back trip for me from the east coast, it’s just not worth it for at most 90 minutes of action before dark. And that’s more likely to be the ceiling than the floor.

 

[Warren Faidley]

Just read all the afternoon wx discussions from DDC, AMA, LBB and OUN and ICT. These are my "go to" decision making teams. Not going to rehash the general vibes, but it's always good to get second opinions about the forecast on a potential big day.

 

[Dan Robinson]

The late timing, models not reliably convecting before sunset (if at all) and the shallow moisture are all things that make me feel the need to back off of chasing this. I think the first two of those could be overlooked if not for the third. We've seen plenty of events like this where storms actually did fire by late evening, and I would not be surprised if one or two did. Some models do have the left exit region of the jet over the dryline at 00z, even if they don't convect. The moisture issue is what I don't think this system can realistically overcome to produce much of any quality.

The late timing also puts into question my ability to get home for Tuesday with adequate rest. A two-day grind is doable with a late enough sleep into Monday, but those usually aren't very fun. I'll be packed and ready to leave tomorrow, but will hold that decision off until the last possible minute.

 

[James Wilson]

The slowing of the system combined with cloud cover over the target area (which seems to be a continued problem in 2024) has me thinking I am sitting Monday out. Models are not showing much and what it is showing is much further west/SW. I have been interested in the NAMs DL bulge in KS but I am likely to resist the urge to go. The long overnight following storms to Iowa/Mo for Tuesday is probably the deal breaker. I live in KC so I will just focus on Tuesday closer to home.

 

[Jamie H]

Can only really concur with other comments. The slowing of the trough, the late overlap with the target area, and shallow moisture would give me pause. That said, I think western OK would be worth a try if I was out there!

 

[Robert Rohloff]

Maybe I am reading these wrong, but it seems to me the dry line is further east than some of the modeling had it. I know it may retreat some but will it actually be further east at the start of the system tomorrow? Any thoughts on this?

 

[Mike Smith]

I think the latest Nadocast has the right idea. I would post it here but both times I've posted one of his forecasts, the moderators have taken it down so go here: Tornado and Severe Thunderstorm Forecast for Monday

I'm not sure where the idea of "too little and not deep enough moisture" is coming from. I went back to yesterday's 12Z HRRR and compared its dew point forecast for 17Z today to the actual 17Z central U.S. surface chart. In every case in southern Oklahoma and northern Texas, the HRRR was forecasting dew points lower than actual -- which has been common this season. In many cases, the difference was 3-4°F.

In terms of depth of moisture, I did the same comparison of the HRRR's forecast sounding at FWD for 12Z today versus actual. The moisture was much deeper than forecast. Even if there was a small moisture over-forecast, the 3,200j of surface CAPE forecast south of Greensburg Monday (latest ECMWF) afternoon is huge for this early in the season. If it is actually 3,000 because the Td was forecast a degree or two too high, what real difference does it make?

Here's today's 12Z ECMWF QPF forecast for the 6-hours ending at 1am Tuesday and it lines up nicely with Nadocast and my thinking. There has been a tendency this season (and it has caught me off-guard a couple of times) for the models to fire convection too late in the afternoon. This event may well be too late for optimal chasing, but if you live in the area, I think it will be worth a (regional) trip.

 

[Dan Robinson]

That is a *massive* cap on this morning's Corpus Christi sounding:

https://weather.ral.ucar.edu/upper/displayUpper.php?img=KCRP.png&endDate=-1&endTime=-1&duration=0

I know that's a little old by this point in the day, but that theme is reflected on forecast soundings throughout the warm sector through midday tomorrow.

The dynamics in the Nebraska secondary target (warm front) look pristine at 00z, and models are firing storms there. The dewpoints are barely hitting 55F by 00z up there though.

I'm packed up for a trip, but haven't felt a need to leave yet.