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Severe Weather Threat May 17-19, 2025

Jbop said:
Do you think the current watch probabilities are a little to high?
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Not necessarily. I agree with the no-call of a PDS watch. There's definitely going to be a lot of tornadoes today, I just question their longevity and strength though. Stuff is already blowing up like crazy, and if there's gonna be intense tornadoes, the discrete cells forming right now need to start cranking as soon as they can before it gets really messy and linear. I hope nothing bad happens.
 
slenker said:
Not necessarily. I agree with the no-call of a PDS watch. There's definitely going to be a lot of tornadoes today, I just question their longevity and strength though. Stuff is already blowing up like crazy, and if there's gonna be intense tornadoes, the discrete cells forming right now need to start cranking as soon as they can before it gets really messy and linear. I hope nothing bad happens.
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I agree with this. Honestly, if we were going to see a PDS tornado watch, it would have and arguably should have happened Friday, and yesterday evening across the moderate risk.
 
DanLarsen34 said:
I agree with this. Honestly, if we were going to see a PDS tornado watch, it would have and arguably should have happened Friday, and yesterday evening across the moderate risk.
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Just to elaborate on this a bit further: both of those days I previously mentioned had background environments that were clearly supportive of violent tornado potential. We had widespread STP values on Friday from the 4-8 range across the moderate risk.

Last night, we had a top-tier parameter space with STP values in excess of 15. That was basically on par with events like April 27, 2011, as well as June 16, 2014 which was the day of the Pilger supercell.

Right now, on the observed mesoscale analysis for the central plains, we have STP values in the 2-3 range. That’s adequate for strong tornadoes, but not necessarily violent tornadoes. In order to get a PDS watch, the SPC has to have a high degree of confidence in at least one violent tornado occurring somewhere in that risk. I believe this is something they’ve said on record before.

Related to this, I believe the STP threshold typically associated with violent tornado environments is considered to be 6+.
 
Seeing all the composite parameters pretty much maxed out last night in Kansas reminded me of what Spann said on 4/27/11 when he saw the STP on the Cordova/Oakman/Parish cell: “look at this thing, 17.5. Guess we’ll see how high this goes today we thought it was a 0-10 scale”
 
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