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Severe WX Severe Weather Threat 4/26-5/1/17

Astronomical forecasting sounding off the 00Z NAM across N. MS 00Z SAT. Parameters as follows:
Near Oxford, MS.
LI - 8.2
LCL 914
SWEATS 514
CAPE 4192
CAP 1.1
Helicity 421
EHI 11.2
BRN 33.3

Now, just where would be the kicker to ignite all this? I can't find it yet. The CAP is not that strong, so......
 
Timhsv said:
Astronomical forecasting sounding off the 00Z NAM across N. MS 00Z SAT. Parameters as follows:
Near Oxford, MS.
LI - 8.2
LCL 914
SWEATS 514
CAPE 4192
CAP 1.1
Helicity 421
EHI 11.2
BRN 33.3

Now, just where would be the kicker to ignite all this? I can't find it yet. The CAP is not that strong, so......
Click to expand...

A weak CAP would shut down the whole thing. That EHI is stupid high... Overdone much?
 
Don't sleep on overnight into tomorrow. A large QLCS will develop and race east across MS later this evening, but will run into better directional shear and will likely break up into segments and become more cellular. It will still be working with a longitudinally narrow warm sector, but a few cells will likely become surface based tomorrow morning. Might briefly increase the tornado threat.

As for the hatched 15% today across LA/AR, it looks to get linear upon initiation. I think they were a bit aggressive in that....
 
I definitely agree about today. The CAMs have this going linear pretty much right away and the area where the best shear and the best instability overlap is pretty small. I guess the NAM is putting up some pretty high sigtor values but I don't think it's very realistic. I think an unhatched 10% tor would have been sufficient.
 
I know this is pretty bold of me to say, but there is pretty much no way that 15% hatched verifies imo. This setup has linear written all over it. The SPC seems really heavy handed with their outlooks this year, and it's a little irritating.
 
Ramped up wording from BMX regarding the threat overnight tonight.

Forecast soundings are rather concerning with 0-6km shear
of 50-65kt and clockwise-curved hodographs yielding 0-1km SRH in
excess of 300 m2/s2. This type of environment will certainly
support a damaging wind and large hail threat, but the tornado
threat will depend on how much of the aforementioned instability
becomes surface-based. Hi-res guidance indicates the potential for
at least a couple of robust surface-based supercells, and a
strong tornado cannot be ruled out if this occurs. The threat
should begin around midnight in the West and continue through 9 AM
Thursday in the East.
Click to expand...
 
Some days I feel like all the physics I was taught in school have changed...only to feel vindicated by a Atmospheric Anti-Climax outlook. This should not be happening. Maybe I am missing something here.
 
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mbrewer said:
Regarding the SPC, just look at 4/15/2011. Stuck with a 15% tornado prob with hatch all day long. I believe it is safe to say these two setups are not that similar. I know it is 6 years ago and a random selection of an Outlook, but I think it is a bit more evidence we're seeing a different approach from the SPC.

http://www.spc.noaa.gov/products/outlook/archive/2011/day1otlk_20110415_1630.html
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Even if you look back to this year's late Feb event from the Ohio Valley with the only EF4 of the year and multiple long trackers, that was a 15% hatched. And it verified nicely.
 
Not only the moderate risks, but three high risks before mid April, not having issued any at all since 2014. And, if ignoring the parameters and going by storm reports alone, a moderate would've probably been sufficient for all three (though at least the most recent one, if not for the wedge and backing, was a very good high risk candidate) Of course the parameters at the time for those days were still pretty impressive, so it's only after the fact we note that only one of those high risk days produced anything higher than an EF2 if I recall, and even that event Atmospheric Anti-Climax for the Florida portion of the high risk. Not sure why they're so aggressive this year. The linear look of today's threat doesn't instill high confidence in today's 15% hatched either... but given what's happened so often in the past, five bucks says it gets almost as bad here as it does in the moderate risk area lol. Gonna be sleeping lightly just in case.
 
SPC is kinda backing off in their own special way on the strong tornado threat in the latest MD. The way they talk about the parameters makes me wonder why they were so bullish in the first place.
 
Equus said:
SPC is kinda backing off in their own special way on the strong tornado threat in the latest MD. The way they talk about the parameters makes me wonder why they were so bullish in the first place.
Click to expand...
The wind profile today is once again, simply not going to cut it for a favorable storm mode or vigorous tornado activity. This was looking linear well in advance, so seeing a 15% hatched tornado driven moderate was very surprising. What isn't surprising is watching everything go linear with no sign of discrete activity. I do not understand why the SPC is being so bullish with tornado probs this year with setups that clearly seem to favor a sloppy/linear mode. It's kind of ridiculous.
 
Moderate risk dropped. You guys were right. How many colors do you think are on the clown shoes they're wearing at the SPC right now?
 
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I will say I am becoming more concerned about the threat for Alabama, west of I-65 in central and northern areas. I could see one or two storms becoming tornadic. The spatial and time parameters are limited, but a couple or 3 supercells are possible..
 
South Central MS and AL....do not ignore tonight and tomorrow morning's potential. Today never looked cellular given the upper level flow is SSW (parallel to the boundary). That shortwave will lift NE tonight and permit a more SW/WSW flow over the narrow warm sector and will permit the QLCS to break up into cells. Some of the shear values are eye opening for overnight....
 
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Kory said:
South Central MS and AL....do not ignore tonight and tomorrow morning's potential. Today never looked linear, given the upper level flow is SSW (parallel to the boundary). That shortwave will lift NE tonight and permit a more SW/WSW flow over the narrow warm sector and will permit the QLCS to break up into cells. Some of the shear values are eye opening for overnight....
Click to expand...
Sounds like we have the same train of thought...
 
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