Severe Weather Threat 5/25-5/26, 2024

[jiharris0220]

...so moisture isn't a problem anymore?

The northern extent of moisture along the dry line being over mixed by excessive temperatures is the problem.

The dew points will need to reach in the mid to high 60s in order to compensate for the temperatures so that the LFC isn’t too high.

The problem is when temperatures reach the 90s, dew points are modeled to drop near the dry line, which screws over any storm trying to become surfaced based.

 

[CheeselandSkies]

There's one poster on here (@Shakespeare 2016?) who seems quite interested in specific temperature/dewpoint values and how they relate to tornado potential. This year ought to be an abject lesson that there's a lot more to getting a favorable thermodynamic profile for tornadoes than that. We had a 26.2 mile EF2 in Wisconsin in February when the dewpoint was about 47-49, and now a day like today.

 

[Clancy]

Leitman commented on Twitter that moisture return was expected and wasn't likely to be an issue, although I still think there's quite a few question marks for this event.

 

[Tempestas Tonitrua]

This may be unpopular because it derails the hype train on WxTwitter, but I just don’t see how this event produces a significant tornado threat. Moisture in the right area and time is still an issue, and is actually now showing up in real time surface obs with how some of the wind vectors are oriented

 

[jiharris0220]

Leitman commented on Twitter that moisture return was expected and wasn't likely to be an issue, although I still think there's quite a few question marks for this event.

Yeah, moisture return isn’t the issue, all of Oklahoma will be in the 60s dew points by 3:00pm, but because of the high temperatures forecasted, the dews along the dry line drop below the 60 mark.

Which is why all of the models only show convection away from the dry line and in northern Tx / southern Ok.

 

[buckeye05]

I think a drop below 15% is warranted in the next outlook.

 

[jiharris0220]

I think a drop below 15% is warranted in the next outlook.

I agree, although not because the tornado threat is lower, violent tornadoes can very much still happen today.

It’s just there’s so much uncertainty on how this could play out it’s now dropped below moderate risk category IMO.

 

[Maxis_s]

I'm noticing that observations are showing a deeper low (998mb observed vs. 1000mb forecasted) and that it's also further south. Will this have any effect on today's setup?

 

[Tempestas Tonitrua]

Might not be the right place for it, but I’ve only actually learned to use models in this hobby for the past 3-4 years.

Is there some sort of retrograding going on with the models as a whole? So many times this year we had instances where the models fell flat on their face relative to actual obs leading up to the event or a huge over performance on a 5% hatched day.

 

[jiharris0220]

Might not be the right place for it, but I’ve only actually learned to use models in this hobby for the past 3-4 years.

Is there some sort of retrograding going on with the models as a whole? So many times this year we had instances where the models fell flat on their face relative to actual obs leading up to the event or a huge over performance on a 5% hatched day.

Here’s what Fred had to say about this.

There's honestly been a consistent wholesale degradation in our high-res model data quality since that poorly-performing Parallel global FV3 that got canned for a year was silently made the operational GFS with no warning back in the spring of 2021.... without them doing anything to fix the documented issues there were with it that caused them to completely can it for a year. Data consistency didn't used to be like this not too long ago back into the past. These days, you can't even get the HRRR to take the radar data it ingests hourly as part of its data assimilation process and just hit copy and paste from 00 hr into 01 hr...

 

[NorthGaWeather]

New discussion no longer uses the v word, so I guess they no longer expect that to occur anymore with confidence, though they use the phrase “substantial tornado production” which isn’t something I’ve seen before.

You also have to take into account individual forecasters and how they phrase things. Violent tornado potential is clearly there.

I haven’t had time to catch up on it this morning, but it seems the potential for high Td depressions and outflow dominance is a real concern. If you have supercells root and maintain, even just one, it will have significant potential. But who knows if that will even occur in OK now. Central Plains events are always so mercurial.

 

[brianc33710]

I know some "weather dweebs" are disappointed" now but I'm sure many/most in KS, OK & TX are perfectly fine with the decreased threat.

 

[jiharris0220]

I know some "weather dweebs" are disappointed" now but I'm sure many/most in KS, OK & TX are perfectly fine with the decreased threat.

The threat hasn’t decreased, the uncertainty has increased.

This event just isn’t the borderline slam dunk it was yesterday, if dew points somehow manage to hold on in the face of 90 degree temps and the low level jet is stronger than modeled; then expect wxtwitter to hound the NWS for not issuing a high risk.

 

[SmokeEater]

10am update from OUN.

Wanted to give a quick summary of some of the trends with the latest 12z data:
Strong agreement now seen in the models on initiation first across our western north Texas or far southwest OK counties along the dryline between 5-6 pm this afternoon. This activity is likely to be initially high-based with a hot, well-mixed boundary layer, posing a risk mainly for large hail and damaging winds (potentially significant), with an initially relatively low tornado threat.
This activity is then expected to move east into southern and central Oklahoma, and there's some question on what the storm mode will be at this point (isolated supercells or more mixed mode). The environment will become increasingly favorable for tornadoes as activity moves eastward, but storm mode may modulate exactly how well storms are able to tap into this environment. Regardless, all severe hazards are still expected across southern/central Oklahoma, with strong tornadoes increasing in likelihood if storms stay more discrete.
Areas to the north may have a bit later initiation (closer to 6-7 pm) across northwest Oklahoma and could end up being a bit more isolated in coverage as it moves eastward this evening. These storms will pose a risk for all severe hazards, with strong tornadoes also possible with this activity as well.

This is how things are looking right now, and of course will be subject to change as new data comes in. We will continue to monitor trends in the observational data regarding moisture return as that may play a big role later on today.

 

[SmokeEater]

Don't see a downgrade happening, and I wouldn't be so fast to say the threat is completely downgraded at 10am local time, lol.

 

[TornadoFan]

 

[Clancy]

Forecast out from Trey.

 

[jiharris0220]

Guys, look at the 12z nam, it’s literally pure hell breaking loose, this is exactly why we need to watch obs today.

 

[Clancy]

Guys, look at the 12z nam, it’s literally pure hell breaking loose, this is exactly why we need to watch obs today.
View attachment 27735

 

[jiharris0220]

What’s interesting is that the nam has a far better handling on current dew points than the hrrr.