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April 24-30th Severe Potential


Chicago Storm

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Issue with that event is that storms got messy after the first 3 hrs due to issues with the wind profile (and also the fact that too many storms went up off the dryline). Still didn't stop it from producing 4 violent tornadoes (I consider the Canton tornado violent) in OK though.

ICT seems concerned about this very same thing. Lastest AFD mentioned that storm mode could get messy possibly.
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DDC

 

Would like to recall April 14, 2012. Models showed the dryline to the east.

On the day of, the dryline and resultant supercells were much farther west.

Again, something to watch.

That's really not true at all.

 

The issue that day was guidance not handling forcing (ascent) and capping all that well, which lead to very early initiation (Before 17z). Thus when initiation occurred, the DL was obviously much further west than anticipated.

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For different reasons.

I deleted that comment because I was gonna re-word it. I suppose you've got a point, but who's to say that morning convection isn't gonna push it back west like that time? As they say, it's something to watch for. Do you think the GFS has small enough resolution to pick up on these cells and their resulting effect?

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Starting to see a tight clustering among the EPS members regarding the surface low position at 00z Wed from W Central KS southward into the TX Panhandle (highest concentration near the KS/OK border). That is basically exactly what you would look for with this type of upper level setup for a major threat to I-35.

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Starting to see a tight clustering among the EPS members regarding the surface low position at 00z Wed from W Central KS southward into the TX Panhandle (highest concentration near the KS/OK border). That is basically exactly what you would look for with this type of upper level setup for a major threat to I-35.

 

Agreed. It's still too far out to get confident with regard to any details, but to the extent that a major threat materializes, the I-35 corridor is increasingly near the center of the distribution of possibilities. I have the most confidence in the threat just a hair E of I-35, Shawnee-Emporia corridor, since a more western dryline solution obviously doesn't prohibit tornadoes there late in the day.

 

Sunday's prospects are piquing my interest more, as well. Model solutions increasingly favor isolated CI in N OK-S KS by 00z. Considering the moderate to high instability, the somewhat-small but still strongly curved hodographs definitely should raise some eyebrows. Intense southeastward-diving supercells with giant hail and a few tornadoes would be a strong possibility, if CI occurs.

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Starting to see a tight clustering among the EPS members regarding the surface low position at 00z Wed from W Central KS southward into the TX Panhandle (highest concentration near the KS/OK border). That is basically exactly what you would look for with this type of upper level setup for a major threat to I-35.

Not to mention the mean SLP ~994mb on the EPS at 00z Wed with several members into the 980s. Pretty impressive.

*Edited to correct MSLP.

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That could be a game changer toward a higher event, that mean is stronger than the GFS op I believe.

In addition to stronger winds aloft with a stronger surface low, you'd undoubtedly keep winds nicely backed ahead of the dryline due to ageostrophic/isallobaric response.
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DDC

 

 

DDC mentioned 4/14/12 but I can't recall that popping up in any of the analogs over the past couple of days. That was an awfully high end event. If the jet core can overspread a wide, open warm sector of 4000+ j/kg of sbcape at peak heating, however, this event has an awfully high ceiling. I'd like to see the 850s back a bit more.

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DDC mentioned 4/14/12 but I can't recall that popping up in any of the analogs over the past couple of days. That was an awfully high end event. If the jet core can overspread a wide, open warm sector of 4000+ j/kg of sbcape at peak heating, however, this event has an awfully high ceiling. I'd like to see the 850s back a bit more.

don't believe they were using it as an analog. Just trying to use it as an example of models being wrong about DL location for a dynamic system like this.
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18z GFS is a textbook outbreak scenario for I-35. The only quibble I can find is that 10-20 kt stronger flow above H5 would be nice. That's a result of the eastern troughing forcing the jet streak more northward as it rounds the base, which could be something to watch in terms of modulating the precise magnitude of the threat (obviously keeping in mind that it's still a high-end tornado threat regardless).

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Although 4/14 is a good MSLP match, that setup in general was more impressive in the upper levels.

 

Yeah - in my mind, these are qualitatively different setups in some important ways. That was a big, lumbering, high-amplitude trough that slowly edged out into the Plains with a positive tilt after a few days. Questions about CI were somewhat founded, as the real upper dynamics lagged behind the warm sector considerably, at least until evening. The flow magnitude was extremely impressive, as you noted, though. To me, the H5 pattern on 14 April was somewhat atypical for such a huge outbreak in the Plains.

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The OUN May 3, 1999 7PM sounding showing up in SARS on several forecasting soundings for the GFS at 00Z. Hmmm.... GFS re-upped the parameters back to what they were a couple days ago. Starting to think more and more that the main bullseye will be Wichita to around Stillwater, and possibly even down to OKC.

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18Z GFS really looking like quite an expansive outbreak. All the way from SC Nebraska southward to NC TX on Tuesday.

As for Saturday (30th), I mentioned in the long/mid range thread yesterday that it has great potential, but it is conditional on a few things, like atmospheric recovery. The wind fields will be very, very impressive. Likely more impressive, at least speed wise, than Tuesday.

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don't believe they were using it as an analog. Just trying to use it as an example of models being wrong about DL location for a dynamic system like this.

 

While they were indeed not using it as an analog, the fact the Tuesday trough looks to be progressive and negatively-tilted, instead of the lumbering positively-tilted system on 4/14/12, suggests that a large last-minute westward jump in dryline position may not be in the cards this goaround.

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Man the 18z GFS really makes the triple point region along the KS/NE border look nasty. Just wicked low level shear profiles there despite more meridional upper level flow. Might get moisture pooling along the warm front (wherever it sets up) for a few significant tornadoes in that area assuming the wind profile doesn't get too messy. Sort of reminiscent of the dipole on 5/6 last year, except on a higher magnitude.

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Pretty crazy - looking at the 18z NAM, it shows EHI of 7+ at 1AM on Tuesday morning along the OK/KS border...

0-1KM EHI nonetheless... :yikes: 18Z NAM and GFS are almost mirror images of each other with the location of the trough and associated jet-core.

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Pretty crazy - looking at the 18z NAM, it shows EHI of 7+ at 1AM on Tuesday morning along the OK/KS border...

 

That's mostly just a function of the nocturnal LLJ intensification, it happens all the time in the Plains by mid-spring. The key is when you actually get strong mid/upper level winds and forcing for ascent overlapping that like we may on Tuesday.

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