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Monday, May 20, 2019 Convective Potential


weatherwiz
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27 minutes ago, RUNNAWAYICEBERG said:

So Steve’s barn was the most damaged from yesterdays plains ‘outbreak’?

Really interesting "null" case on a high risk actually.

Ryan pointed out on Twitter last night that there was a little WAA/subsidence over OK that capped things a bit, but also you had really weak 0-3 km lapse rates (5.3 C/km). The analog event (April 2011) BMX had 8.8 C/km.

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1 minute ago, OceanStWx said:

Really interesting "null" case on a high risk actually.

Ryan pointed out on Twitter last night that there was a little WAA/subsidence over OK that capped things a bit, but also you had really weak 0-3 km lapse rates (5.3 C/km). The analog event (April 2011) BMX had 8.8 C/km.

HM (who sadly doesn't post here anymore) also pointed something out...mentioned that increased H7 fronto and winds actually helped to slightly increase H7 temps over SE OK...which alludes to the cap which appeared on the sounding. llvl lapse rates were pretty crap as you pointed out. 

All in all though I don't think the forecast could have...or should have been handled any differently. the negating factors I think were more mesoscale driven. I know busts suck and hurt credibility, but given what was potentially at stake and the population density you can't "downplay" potential like that...unless you have glaring flags. 

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4 minutes ago, weatherwiz said:

HM (who sadly doesn't post here anymore) also pointed something out...mentioned that increased H7 fronto and winds actually helped to slightly increase H7 temps over SE OK...which alludes to the cap which appeared on the sounding. llvl lapse rates were pretty crap as you pointed out. 

All in all though I don't think the forecast could have...or should have been handled any differently. the negating factors I think were more mesoscale driven. I know busts suck and hurt credibility, but given what was potentially at stake and the population density you can't "downplay" potential like that...unless you have glaring flags. 

I think too much cloud cover (maybe as a result of all the WAA) limited 0-3 km lapse rates. If WAA was elevated to start there was no mechanism to draw in surface air. If you aren't surface based you aren't getting tornadoes.

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1 minute ago, OceanStWx said:

I think too much cloud cover (maybe as a result of all the WAA) limited 0-3 km lapse rates. If WAA was elevated to start there was no mechanism to draw in surface air. If you aren't surface based you aren't getting tornadoes.

I forget who it was but I saw a tweet that showed the 0-3km lapse rates late afternoon over OK...never even thought to check them during the day but it sort of crossed my mind that could be concerning and then never really soaked it in. Thought perhaps they would steepen as models I believed showed. 

I think I saw several other posts too which really gave CAMS credit in which several never really hit on the idea of discrete supercells in the warm sector. I wasn't sure I totally agreed with this...I had always thought it was going to be a line of supercells which would develop (right where the QLCS organized) (with some discrete ahead too)...but there was just so much going on. 

Another issue too was storm motion with respect to the shear. 

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7 minutes ago, weatherwiz said:

I forget who it was but I saw a tweet that showed the 0-3km lapse rates late afternoon over OK...never even thought to check them during the day but it sort of crossed my mind that could be concerning and then never really soaked it in. Thought perhaps they would steepen as models I believed showed. 

I think I saw several other posts too which really gave CAMS credit in which several never really hit on the idea of discrete supercells in the warm sector. I wasn't sure I totally agreed with this...I had always thought it was going to be a line of supercells which would develop (right where the QLCS organized) (with some discrete ahead too)...but there was just so much going on. 

Another issue too was storm motion with respect to the shear. 

Well there is a bias for some CAMs to over-mix the boundary layer, which would artificially enhance low level lapse rates. RAP/HRRR models would definitely be in this camp.

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10 minutes ago, OceanStWx said:

Well there is a bias for some CAMs to over-mix the boundary layer, which would artificially enhance low level lapse rates. RAP/HRRR models would definitely be in this camp.

I feel like there are some model biases which have been becoming worse over the last several years lol. I'm sort of surprised though the CAMS would be in that regard considering it always seems like the GFS is super aggressive with mixing and the NAM isn't. 

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1 minute ago, weatherwiz said:

Like look at this for SDF tomorrow between the NAM (top) and GFS (bottom)...although if I change the Momentum Xfer option to 10 then the output for wind is similar to the GFS. 

I'm not positive of all the parameterization schemes for the CAMs, but they are designed to overturn the atmosphere. So sometimes they do it in an environment that isn't going to turn over.

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3 minutes ago, OceanStWx said:

I'm not positive of all the parameterization schemes for the CAMs, but they are designed to overturn the atmosphere. So sometimes they do it in an environment that isn't going to turn over.

well I could imagine the equations needed and the physics for the models to differentiate when to overturn and when not too can be extremely, extremely complex and probably require a ton of computing power. So that's where the expertise of a forecaster would have to come in. 

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7 hours ago, CT Rain said:

FWIW, the SREF and NAM are showing the potential for some legit tornado action in NY/PA on Thursday. Really impressive overlap of parameters. 

Some of those soundings in PA are nuts...nearly a 90 degree turn of the wind from the sfc to 700. 

Both the NAM/euro show some vorticity ahead of the main s/w trough and that is looking to blow through very quickly which could really put a damper on the potential. Assuming this modeled energy is legit. 

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