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April 24-30th Severe Potential

Chicago Storm

By Chicago Storm,
in Central/Western States

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Chicago Storm

Chicago Storm

Posted
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Posted

For Tuesday, the concerns are warranted in light of how incredibly hyped this event has been from a week out. It's probably among the most hyped I can ever remember from that early on, and I'm beginning to seriously doubt it will fulfill those lofty expectations.

Yes, there's huge CAPE and a big trough coming in, and there will probably be some tornadoes. But it's all relative to expectations, which couldn't be higher, for a lot of the community.

A couple days ago, I said the caveats for this setup didn't really look any worse than they did from the same lead time for 4/14/12. That's clearly no longer the case -- there are serious issues showing up on virtually all the current progs. The cyclone is occluding too early, and unless that trend reverses quickly, it will limit the threat of a dryline tornado outbreak considerably. There could still be tornadic supercells on the dryline, but probably not extremely long-track violent tornadoes. Closer to the WF (anywhere from C KS to C NE/W IA, depending on what you believe) still looks pretty ominous, and may end up being the real bullseye if trends hold.

Agree with the above.

VBV, crossovers, and capping are all concerns of mine, among other things. The triple point/near WF area is where I'm eyeing at thing point. Looks like an increasing consensus of that being in NE/SW. IA/NE. KS.

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capbreak

capbreak

Posted
Posted

The one nice thing about this setup now is that playing the warm front vs the dryline is an easier decision as someone not coming up from OK/TX. With capping we also probably won't have any early convection messing up the warm front either, like we did on 4/14/12.

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jojo762

jojo762

Posted
Posted

GFS at 00z wednesday has surface winds with a SW component in OKC...I'm thinking this is due to convection...any thoughts?

Looks like it could be convectively caused, but also, it looks as though OKC is ever so slightly west of the dryline, if not right under it on the 12Z GFS @00Z.

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OUGrad05

OUGrad05

Posted
Posted

Looks like it could be convectively caused, but also, it looks as though OKC is ever so slightly west of the dryline, if not right under it on the 12Z GFS @00Z.

What it looked like to me...I can't see the counties on mine for some reason, so I was just guessing location when I clicked...

GFS has sped things up a reasonable amount over prior runs.  

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bdgwx

bdgwx

Posted
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The 12Z NAM not showing much convection even by 0Z is only mildly noteworthy to me to right now. That can and probably will change as we get closer. The more interesting mitigating factors are a weakening mid level jet streak, mid level winds with a significant southern component, 0-6km shear that really isn't that impressive, 0-1 SRH that is actually astonishingly low relative to the hype. This isn't what high risk outbreaks are made of. Call me conservative, but unless we start seeing an uptick in favorable outbreak conditions I have to agree with the others that current data does not support the hype.

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OUGrad05

OUGrad05

Posted
Posted

The 12Z NAM not showing much convection even by 0Z is only mildly noteworthy to me to right now. That can and probably will change as we get closer. The more interesting mitigating factors are a weakening mid level jet streak, mid level winds with a significant southern component, 0-6km shear that really isn't that impressive, 0-1 SRH that is actually astonishingly low relative to the hype. This isn't what high risk outbreaks are made of. Call me conservative, but unless we start seeing an uptick in favorable outbreak conditions I have to agree with the others that current data does not support the hype.

Helicity values are very low.  CAPE will be enough to fuel some significant storms, probably an EF2 tornado along the way...but hard to see long lived tornadoes with the current setup, at least in OK.  Things better come together quickly....

Looks to be a monster hail event though.

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andyhb

andyhb

Posted
Posted

The 12Z NAM not showing much convection even by 0Z is only mildly noteworthy to me to right now. That can and probably will change as we get closer. The more interesting mitigating factors are a weakening mid level jet streak, mid level winds with a significant southern component, 0-6km shear that really isn't that impressive, 0-1 SRH that is actually astonishingly low relative to the hype. This isn't what high risk outbreaks are made of. Call me conservative, but unless we start seeing an uptick in favorable outbreak conditions I have to agree with the others that current data does not support the hype.

 

Even near the triple point through 00z, these values are quite low, which is pretty damning for the whole thing.

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jojo762

jojo762

Posted
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Eh. 200+m2/s2 of 0-1KM SRH at and after 00Z along the DL in KS/OK certainly isn't that high, but it's not absolutely terrible... Perhaps what is more unimpressive is 0-3KM SRH may not reach or be much better at all than 250m2/s2. However, previous runs, like from yesterday, did have better-- and in certain cases much better-- SRH. Not trending in the right direction today...

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jojo762

jojo762

Posted
Posted

mcd0437.gif

MESOSCALE DISCUSSION 0437
NWS STORM PREDICTION CENTER NORMAN OK
0150 PM CDT SUN APR 24 2016

AREAS AFFECTED...CNTRL KS INTO NWRN OK

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY

VALID 241850Z - 242115Z

PROBABILITY OF WATCH ISSUANCE...80 PERCENT

SUMMARY...WIDELY SCATTERED CONVECTIVE INITIATION IS LIKELY DURING
THE 20-22Z PERIOD OVER KS AND ISOLATED CONVECTIVE INITIATION IS
PROBABLE DURING THE 22-01Z PERIOD FROM THE KS-OK BORDER REGION SWD
INTO OK. LARGE TO VERY LARGE HAIL WILL BE POSSIBLE WITH STRONGER
UPDRAFTS THAT DEVELOP INTO SUPERCELLS. A MODEST WEAK-TORNADO RISK
WILL BE CONFINED TO THE EARLY EVENING /23-02Z/ WHEN LOW-LEVEL SHEAR
STRENGTHENS AND TEMP/DEWPOINT SPREADS LOWER.

DISCUSSION...18Z SURFACE ANALYSIS PLACES A SHARPENING
DRYLINE/CONFLUENT LOW-LEVEL FLOW FROM 25 MI W RSL SWD ALONG THE
TX-OK BORDER. DEWPOINTS HAVE RISEN INTO THE 59-62 DEG F RANGE
DURING THE PAST FEW HOURS IN W-CNTRL OK PER OK MESONET OBSERVATIONS.
STRONG HEATING COUPLED WITH GRADUAL MOISTENING ARE CONTRIBUTING TO
MODERATE BUOYANCY. WATER VAPOR IMAGERY SHOWS A WELL-DEFINED
MID-LEVEL VORTICITY MAXIMUM ROTATING THROUGH THE BASE OF
LARGER-SCALE TROUGH ACROSS W-CNTRL KS EARLY THIS AFTERNOON. THIS
FEATURE WILL MOVE INTO CNTRL AND ERN PORTIONS OF KS/S-CNTRL NEB BY
LATE AFTERNOON. THE TRAILING PORTION OF THIS FEATURE AND IMPLIED
WEAK ASCENT WILL SPREAD ACROSS NWRN OK DURING THE LATE
AFTERNOON/EARLY EVENING.

SURFACE OBSERVATIONS DURING THE PAST FEW HOURS IMPLY THE SPC
RAP-BASED OBJECTIVE ANALYSES ARE SUFFERING FROM THE RAP OVER-MIXING
DRY BIAS YIELDING AN UNDER-REPRESENTATION OF LOW-LEVEL MOISTURE.
WRF-BASED GUIDANCE /PARTICULARLY THE NAM/ APPEARS TO EXHIBIT A MORE
REASONABLE SOLUTION REGARDING MOISTURE/MIXING AND SUBSEQUENT CAP
EROSION AND CONVECTIVE INITIATION PROCESSES.

CONVECTIVE INITIATION WILL LIKELY OCCUR FIRST ACROSS CNTRL KS ALONG
THE DRYLINE AND GRADUALLY INCLUDE AREAS FARTHER S ALONG THE KS/OK
BORDER BY LATE THIS AFTERNOON AND INTO NWRN OK DURING THE EARLY
EVENING HOURS. DEEP SHEAR VECTORS ORIENTED ORTHOGONAL TO THE
SURFACE BOUNDARIES COUPLED WITH EFFECTIVE SHEAR MAGNITUDES OF 40-50
KT WILL FAVOR DISCRETE SUPERCELL MODE WITH THE STRONGER/SUSTAINED
UPDRAFTS. LOW-LEVEL SHEAR /I.E. SRH/ RISES INTO THE 100-250 M2/S2
RANGE DURING THE 23-02Z PERIOD AND WILL GENERALLY COINCIDE WITH SOME
WEAK TORNADO POTENTIAL WITH ANY STRONGER/SUSTAINED SUPERCELL.
STRENGTHENING CONVECTIVE INHIBITION AFTER 01-02Z WILL TEND TO
RESTRICT STORM INTENSITY/COVERAGE THIS EVENING AS MOST OF THE
ACTIVITY DIMINISHES.

..SMITH/CORFIDI.. 04/24/2016

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OUGrad05

OUGrad05

Posted
Posted

Eh. 200+m2/s2 of 0-1KM SRH at and after 00Z along the DL in KS/OK certainly isn't that high, but it's not absolutely terrible... Perhaps what is more unimpressive is 0-3KM SRH may not reach or be much better at all than 250m2/s2. However, previous runs, like from yesterday, did have better-- and in certain cases much better-- SRH. Not trending in the right direction today...

200+m2/s2 is adequate for tornadoes for sure, but not indicative of some sort of massive outbreak and isn't really supportive for widespread strong or violent tornadoes...one offs are always possible.

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jojo762

jojo762

Posted
Posted

Might be somewhat interesting here in a bit. Looks like initiation should take place soon across SW/SC KS, probably somewhere near KPTT and KGBD, also some nice looking CU in NW OK. Here is the UH-tracks for today from the 18Z HRRR.  HRRR has been persistent for much of today in showing a nice supercell going north of ICT and into EC/SC KS. Obviously the parameters are not anything too impressive, but still might get a couple nice supercells toward 00z. Storms will be pretty high based at first given pretty high LCLs.

post-7962-0-28359400-1461525978_thumb.pn

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jojo762

jojo762

Posted
Posted

A little off topic here, but Pivotalweather now has three different WRF models. Reflectivity, CAPE, and updraft helicity are the only forecast fields.

Pretty useful stuff. The WRF-NSSL on there actually has a lot more forecasts fields than just those three.

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wildwestpb

wildwestpb

Posted
Posted

Yxaq9N4.gif

URGENT - IMMEDIATE BROADCAST REQUESTED   TORNADO WATCH NUMBER 102   NWS STORM PREDICTION CENTER NORMAN OK   300 PM CDT SUN APR 24 2016   THE NWS STORM PREDICTION CENTER HAS ISSUED A   * TORNADO WATCH FOR PORTIONS OF      CENTRAL AND EASTERN KANSAS     NORTHERN OKLAHOMA   * EFFECTIVE THIS SUNDAY AFTERNOON AND EVENING FROM 300 PM UNTIL     1100 PM CDT.   * PRIMARY THREATS INCLUDE...     A COUPLE TORNADOES POSSIBLE     WIDESPREAD LARGE HAIL EXPECTED WITH ISOLATED VERY LARGE HAIL       EVENTS TO 3 INCHES IN DIAMETER LIKELY     SCATTERED DAMAGING WINDS LIKELY WITH ISOLATED SIGNIFICANT GUSTS       TO 75 MPH POSSIBLE   SUMMARY...A FEW SUPERCELL STORMS WITH A THREAT FOR VERY LARGE   HAIL...LOCALLY DAMAGING WIND...AND A TORNADO OR TWO EXPECTED TO   DEVELOP AND MOVE GENERALLY EAST-NORTHEAST ACROSS CENTRAL AND EASTERN   KANSAS LATER TODAY INTO TONIGHT. A MORE ISOLATED SEVERE THREAT   SOUTHWARD INTO PARTS OF OKLAHOMA ALSO MAY PERSIST THROUGH LATER   TONIGHT.   THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 75 STATUTE   MILES EAST AND WEST OF A LINE FROM 60 MILES NORTH OF MANHATTAN   KANSAS TO 25 MILES WEST SOUTHWEST OF ENID OKLAHOMA.  FOR A   COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE   UPDATE (WOUS64 KWNS WOU2).
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jojo762

jojo762

Posted
Posted

18Z NAM is much more impressive across the dryline in OK and near the triple-point. It is a tad further west, so it keeps I-35 in play. This is at 03Z in NC OK... The best window for tornadoes may be relatively confined to a few hours though, as VBV becomes an issue later on in the night it appears.

post-7962-0-30248300-1461530235_thumb.pn

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jojo762

jojo762

Posted
Posted

Just a note, if this doesn't bust, this better be called the "I-35 Tornado Outbreak" and not April 26, 2016. This due to too many outbreaks that have happened on this date. 

But there has been so many different I-35 Tornado Outbreaks?

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ZackH

ZackH

Posted
Posted

It's nice to see the surface cyclone actually deepening in a cursory glance at the 18z NAM. The 500mb flow also seems to be a little less meridional with more of a southwesterly component over most of KS and OK. Right now I personally like the triple point and just south of the triple point on the dryline. There is a really nice bulge that should enhance convergence. Still... The flow is really amplified... More than I'd like to see but this would be chaseable.

Sent from my iPhone using Tapatalk

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