Oklahoma Severe Weather Discussion - May 2012

[venture]

MESOSCALE DISCUSSION 0963
NWS STORM PREDICTION CENTER NORMAN OK
0306 PM CDT TUE MAY 29 2012

AREAS AFFECTED...SW KS...WRN OK...NW TX

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY

VALID 292006Z - 292130Z

PROBABILITY OF WATCH ISSUANCE...95 PERCENT

SUMMARY...A SEVERE THREAT IS EXPECTED TO DEVELOP ACROSS SW
KS...WCNTRL OK AND NW TX LATE THIS AFTERNOON. LARGE HAIL AND WIND
DAMAGE SHOULD BE THE PRIMARY THREATS ALTHOUGH AN ISOLATED TORNADO
THREAT MAY ALSO DEVELOP. WW ISSUANCE WILL BE LIKELY BY 2130Z.

DISCUSSION...LATEST SFC ANALYSIS SHOWS A 1007 MB SFC LOW NEAR
CHILDRESS WITH A MOIST AXIS EXTENDING NWD FROM NORTH TX INTO WRN OK
WHERE SFC DEWPOINTS ARE IN THE UPPER 60S F. WARMING SFC TEMPS ALONG
THE MOIST AXIS HAVE RESULTED IN THE DEVELOPMENT OF STRONG
INSTABILITY ACROSS THE MCD AREA. MESOANALYSIS IS ESTIMATING MLCAPE
VALUES ARE NOW IN THE 3000 TO 4500 J/KG RANGE. IN ADDITION...THE
CAPPING INVERSION HAS DIMINISHED ACROSS MOST OF WRN OK AND PARTS OF
SW KS WHERE STORM INITIATION IS EXPECTED TO TAKE PLACE AROUND 21Z.
SHORT-TERM MODEL FORECASTS SUGGEST THE FAVORED ZONE FOR INITIATION
WILL BE FROM GAGE OK ARCHING SWD ACROSS WRN OK AND BACK SWWD INTO NW
TX WHERE SEVERAL FIELDS OF CUMULUS ARE BECOMING AGITATED ACCORDING
TO VISIBLE SATELLITE IMAGERY. REGIONAL PROFILERS FROM SW KS INTO WRN
OK HAVE 0-6 KM SHEAR OF 35 TO 45 KT WITH STRONG DIRECTIONAL SHEAR
FROM 1 KM TO 4 KM AGL. THE SHEAR ENVIRONMENT ALONG WITH STEEP
MID-LEVEL LAPSE RATES AND STRONG INSTABILITY...SHOULD BE FAVORABLE
FOR SUPERCELLS WITH LARGE HAIL. HAIL GREATER THAN 2 INCHES IN
DIAMETER AND A TORNADO OR TWO WILL BE POSSIBLE WITH THE MORE
DOMINANT SUPERCELLS. AS STORMS INCREASE IN COVERAGE AND CELL MERGERS
OCCUR...A SEVERE MCS APPEARS LIKELY. THE WIND DAMAGE THREAT SHOULD
INCREASE BY EARLY EVENING ESPECIALLY IF A WELL-DEVELOPED BOWING LINE
SEGMENT CAN ORGANIZE ACROSS CNTRL OK.

..BROYLES/BUNTING/WEISS.. 05/29/2012

[venture]

Things are starting to go now in SW KS. Watch will be up shortly.

[venture]

Ww 317 severe tstm ks ok tx 292055z - 300400z
axis..85 statute miles east and west of line..
25nw p28/medicine lodge ks/ - 30wsw adm/ardmore ok/ ..aviation coords.. 75nm e/w /64w ict - 17wsw adm/ hail surface and aloft..3 inches. Wind gusts..70 knots.
Max tops to 550. Mean storm motion vector 29025.

Hazard Tornadoes EF2+ Tornadoes Likelihood Low Very Low

Severe Wind 65 kt+ Wind High Low

Severe Hail 2"+ Hail High Moderate

Tornadoes

Probability of 2 or more tornadoes	Low (20%)
Probability of 1 or more strong (F2-F5) tornadoes	Low (5%)

Wind

Probability of 10 or more severe wind events	High (70%)
Probability of 1 or more wind events > 65 knots	Low (20%)

Hail

Probability of 10 or more severe hail events	High (70%)
Probability of 1 or more hailstones > 2 inches	Mod (40%)

Combined Severe Hail/Wind

Probability of 6 or more combined severe hail/wind events

High (80%)

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 317
NWS STORM PREDICTION CENTER NORMAN OK
355 PM CDT TUE MAY 29 2012

THE NWS STORM PREDICTION CENTER HAS ISSUED A
SEVERE THUNDERSTORM WATCH FOR PORTIONS OF

FAR SOUTHWEST AND SOUTH CENTRAL KANSAS
WESTERN AND CENTRAL OKLAHOMA
A SMALL PART OF NORTHWEST TEXAS

EFFECTIVE THIS TUESDAY AFTERNOON AND EVENING FROM 355 PM UNTIL
1100 PM CDT.

SCATTERED DAMAGING WINDS TO 80 MPH
SCATTERED LARGE HAIL
ISOLATED HAIL TO 3.0 INCHES IN DIAMETER POSSIBLE
ISOLATED TORNADOES

THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 85
STATUTE MILES EAST AND WEST OF A LINE FROM 25 MILES NORTHWEST OF
MEDICINE LODGE KANSAS TO 30 MILES WEST SOUTHWEST OF ARDMORE
OKLAHOMA. FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU7).

REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE
FAVORABLE FOR SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
AND POSSIBLE WARNINGS. SEVERE THUNDERSTORMS CAN AND OCCASIONALLY
DO PRODUCE TORNADOES.

OTHER WATCH INFORMATION...CONTINUE...WW 313...WW 314...WW
315...WW 316...

DISCUSSION...VISIBLE IMAGERY SHOWS CU/TCU FIELD DEVELOPING FROM SWRN
KS INTO NWRN OK...AND WITH CAP CONTINUING TO WEAKEN...DEEP
CONVECTION IS EXPECTED TO DEVELOP WITHIN THE NEXT 1-2 HRS ACROSS
PARTS OF SWRN KS AND WRN OK. STEEP LAPSE RATES AND WARM SURFACE
TEMPERATURES WITH INCREASING MOISTURE OVER OK ARE CONTRIBUTING TO
VERY UNSTABLE CONDITIONS WITH MLCAPE OF 2500-3500 J/KG. VEERING
WINDS WITH HEIGHT AND RESULTANT STRONG DIRECTIONAL SHEAR WILL
PROVIDE A FAVORABLE ENVIRONMENT FOR INITIAL SUPERCELL DEVELOPMENT
WITH STORMS CAPABLE OF PRODUCING VERY LARGE HAIL AND DAMAGING WINDS.
STORMS MAY GROW UPSCALE INTO A SEWD MOVING MCS LATER THIS EVENING
WITH AN INCREASING THREAT FOR MORE WIDESPREAD DAMAGING WINDS.

AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
TO 3 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 70
KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 550. MEAN STORM
MOTION VECTOR 29025.

[venture]

New cell going up fast in Blaine/Major counties just SW of Fairview...

Most attention will be on the chat room now as things are going to go very fast.

[venture]

Severe

Thunderstorm Warning for Alfalfa, Woods [OK] till 5:30 PM CDT

Major County storm is increasing now and the storms in the SW are picking up a little steam as well.

[venture]

Closer to the Metro:

Severe Thunderstorm Warning for Alfalfa, Blaine, Garfield, Grant, Kingfisher, Major [OK] till 6:30 PM

Also a new tower trying to go up between Hydro and Bridgeport.

[adaniel]

It looks like the line forming is weakest in the middle.

Is there a cap or something similar in place over the central part of the state?

[jn1780]

The storm northwest of the city seems very familiar to the storm a few years ago that caused all that hail damage. Hope this won't be the case.

[venture]

Game of squeeze play for the Metro area coming up. Severe storm in Kingfisher Co moving SE will impact the Northern Metro area. Another severe storm moving NE out of Caddo County will impact the Southern Metro area...as it looks now.

[venture]

Tornado

Warning for Canadian, Oklahoma [OK] till 9:00 PM CDT

[venture]

Full attention is at the chat right now. Two storms with increasing rotation to the west in Canadian County. Hail sizes seem to be getting more reasonable now, but strong winds/heavy rain still very possible.

[Roadhawg]

I got hit hard by the hail... several shattered windows on the south side

[Richard at Remax]

I was trying to leave 50 penn place in time but got trapped there. I ran up on a curb and parked under a tree. still have bumps on the car but no window damage. could have been a lot worse for me. but I saw cars just get shattered

[BlackmoreRulz]

We lost power here in Edmond for well over an hour...had a few 3" diameter hail stones

[kevinpate]

Small hail. Wind enough to snap a small treeee. Not enough to topple far larger dead tree ... Drat.
Poeer out my block anyay, couple of hours now. Sad am I. My cpap is askeered of the dark, or something like that. Sure wish it wasn't though.

[venture]

MODERATE RISK for TODAY (Wednesday)
Area: West of a line from Medford to Stillwater to Wewoka to Coalgate to Durant
Risk Values: Tornado (10%), Significant Wind (30%), Significant Hail (45%)

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1253 AM CDT WED MAY 30 2012

VALID 301200Z - 311200Z

...THERE IS A MDT RISK OF SVR TSTMS ACROSS WRN AND CENTRAL OK/N TX
AND A SMALL PORTION OF SRN KS...

...THERE IS A SLGT RISK OF SVR TSTMS EXTENDING FROM PARTS OF WRN NEB
SWD INTO N TX/SWRN MO/WRN AR...

...SYNOPSIS...
BROAD/WEAK TROUGHING OVER THE ERN U.S. IS FORECAST TO BECOME
REINFORCED ON ITS WRN FRINGE AS SHORT-WAVE TROUGHING MOVES OUT OF
THE ROCKIES AND INTO THE CENTRAL U.S. THROUGH THE PERIOD.

AT THE SURFACE...DEPARTING T.D. BERYL IS PROGGED TO BE SHIFTING OFF
THE SERN U.S. COAST EARLY...LEAVING A WEAK WIND SHIFT/CONVERGENCE
AXIS IN ITS WAKE -- EXTENDING WWD ALONG THE GULF COAST REGION.
MEANWHILE...LOW PRESSURE IS FORECAST TO REMAIN INVOF NWRN TX DURING
THE DAY...WITH A COMBINATION FRONT/OUTFLOW EXTENDING EWD ACROSS THE
OK VICINITY AND A DRYLINE EXTENDING SWD. THESE TWO BOUNDARIES IN
THE OK/TX VICINITY AND THE WIND SHIFT ACROSS THE GULF COAST REGION
SHOULD SERVE AS THE PRIMARY CONVECTIVE FOCI THIS PERIOD.

...PARTS OF THE CENTRAL AND SRN PLAINS REGION...
ANOTHER DAY OF SUBSTANTIAL SEVERE WEATHER POTENTIAL IS EXPECTED
ACROSS THE OK/TX VICINITY...WITH SOME THREAT EXTENDING NWWD INTO THE
CENTRAL HIGH PLAINS REGION. ACROSS THE SRN
PLAINS...HEATING/DESTABILIZATION IS FORECAST IN THE WAKE OF
OVERNIGHT CONVECTION -- AND AN ASSOCIATED OUTFLOW BOUNDARY WHICH
SHOULD BE RETREATING NWD ACROSS THE RED RIVER VALLEY/SRN OK DURING
THE DAY. BY MID TO LATE AFTERNOON...THIS BOUNDARY -- EXPECTED TO
RESIDE ACROSS CENTRAL OR NRN OK...AND A DRYLINE MIXING EWD ACROSS
THE TX PANHANDLE/NWRN TX TOWARD WRN OK...WILL LIKELY FOCUS UPDRAFT
INITIATION -- AIDED BY THE A SUBTLE FEATURE ALOFT WHICH SHOULD BE
SHIFTING INTO THE SRN HIGH PLAINS.

WITH VERY STEEP MID-LEVEL LAPSE RATES BEING CONTINUALLY SUPPLIED BY
WLY FLOW ALOFT -- SPREADING ATOP A MOIST/HEATING BOUNDARY
LAYER...STRONG DESTABILIZATION WILL OCCUR...WITH AFTERNOON CAPE
VALUES OVER WRN OK AND VICINITY FORECAST TO EXCEED 4000 J/KG
MIXED-LAYER CAPE. THIS THERMODYNAMIC ENVIRONMENT WILL ALLOW
EXPLOSIVE CONVECTIVE GROWTH ONCE STORMS INITIATE...FURTHER AIDED BY
DEEP-LAYER SHEAR SUPPORTIVE OF UPDRAFT ROTATION. ISOLATED STORMS
DEVELOPING ACROSS WRN OK AND VICINITY WILL LIKELY PRODUCE VERY
LARGE/DAMAGING HAIL...AND WILL ALSO BE CAPABLE OF PRODUCING DAMAGING
WINDS. WHILE SOMEWHAT WEAK LOW-LEVEL FLOW MAY LIMIT TORNADO
POTENTIAL IN MOST AREAS...ENHANCED SHEAR NEAR/N OF THE SURFACE
FRONT/REMNANT OUTFLOW MAY SUPPORT A ZONE OF SLIGHTLY HIGHER TORNADO
PROBABILITY.

MORE ISOLATED STORMS MAY ALSO DEVELOP NWWD ACROSS THE CENTRAL HIGH
PLAINS REGION...WHERE LESSER -- BUT SUFFICIENT -- INSTABILITY WILL
SUPPORT SOME HAIL/WIND POTENTIAL.

AS STORMS INCREASE IN COVERAGE ACROSS OK AND VICINITY...COLLIDING
STORM OUTFLOWS COMBINED WITH THE DEGREE OF INSTABILITY SUGGEST THAT
STORM CLUSTERING/UPSCALE GROWTH IS LIKELY INTO THE EVENING. ALONG
WITH VERY LARGE HAIL AND ISOLATED TORNADO POTENTIAL WITH ROTATING
CELLS...WIND POTENTIAL SHOULD INCREASE -- WITH STORMS EVENTUALLY
FORECAST TO SHIFT EWD ACROSS OK/N TX LIKELY IN THE FORM OF ONE OR
MORE MCS/S.

[PennyQuilts]

So sorry for all the people with damage from last night's storm. I checked the house, this morning, and other than twigs, two seed grown tomato plants and a cajun pepper plant that deserved to die, anyway, we didn't have any damage. I am amazed that is so because we got lots of rain, high winds and two inch hail.

[NoOkie]

So sorry for all the people with damage from last night's storm. I checked the house, this morning, and other than twigs, two seed grown tomato plants and a cajun pepper plant that deserved to die, anyway, we didn't have any damage. I am amazed that is so because we got lots of rain, high winds and two inch hail.

I got off pretty lightly. The worst that happened to me was my already damaged fence blew over twice(First it fell one way, then the wind shifted and flipped it over the other way) and my flowers got shredded. Tons of trees down in my neighborhood, though. I had to zig zag around them on my way to work.

[Roadhawg]

Large hail, lots of rain and wind here. Total of 8 broken out windows on the south side and the hail hit hard enough to ruin the blinds over the windows. Large tree limb down in the back yard too.

[bandnerd]

Managed to get out just fine here. I was worried about my little garden plot, but dang if it doesn't look happier today than it's looked so far this spring. Weird. It was hard to sleep this morning with the hail on the roof.

Hey, venture, about what time are we looking for today's weather to start?

[Roadhawg]

I was wondering what's going to happen today too

[venture]

Now to a topic those that suffered damage yesterday don't want to hear...Round 2.

Morning model guidance is indicating that the activity going on right now should continue to push east and skies remain mostly clear back to the West and North. Now the setup for today is a bit complex so I wanted to point out all the main features for today.



So we have the main storm system out in the TX PH today that will be pulling out. The stationary front has moved north over Northern OK. Then as you can see on the graphic we have several outflow boundaries (black lines). These can become a focal point for development later and could also provide enhanced areas of storms to intensify/rotate later on. Current the atmosphere is fairly worked over behind the complex moving south. Instability is pretty low right now, but should rebound pretty quickly. In the next few hours we are expecting instability to become extreme especially from the OKC area and back to the west.

HRRR model is showing things should start to pop around 4-6PM across Western OK. We should also be looking at a developing complex across Western KS that will likely drop south as a strong complex with the potential for widespread damaging winds. These initial storms will have the risk of very large to giant hail and tornadoes. The greatest risk for those will be across NW OK and W KS. Then like we have seen in past years (think 2001 and 2006?) and even a bit yesterday, they will combine into a large forward moving bow complex. The threat will transition quickly from large hail and tornadoes to significant widespread destructive winds. As we saw yesterday we had many reports of 80 mph or higher. It would not be out of the realm of possibility that we could see widespread 70-90 mph winds with the MCC/MCS. These are typically called Derechos and here is a quick info page on a major one we had about 10 years ago: http://www.spc.noaa.gov/misc/AbtDere...282001page.htm.

More Derecho Info: http://www.spc.noaa.gov/misc/AbtDere....htm#srnplains

So main rule today is be prepared, have things secured down that didn't fly away last night, and just be prepared. We'll see a new SPC outlook out here soon, but as of right now the Moderate Risk area (most likely area for the above mentioned activity) covers nearly all of Western and Central OK - including the Metro Area.

[Kaye]

Thank you for the update Venture! I have a question concerning the HRRR model. I know you have a link to it posted on the first page of this thread but am having trouble using it. I don't know what I'm looking at and what I should select. Yesterday you posted the HRRR and it looped to show convective development and motion, etc. What do I need to do to be able to look at the information myself today and going forward? I understand if you don't have time to do this today, but at some point a quick tutorial would be nice. I get lost trying to figure it out.

[adaniel]

I went through a derecho in 2006 in St Louis. They are every bit as scary as a tornado. This occurred during the same weekend as the opening of the new Busch Stadium, and several people were hurt very badly during a Cardinals game. The best way I would describe it is 3-5 minutes of howling 70-80 mph winds (no gusts just straight unrelenting winds). Since they are huge geographically there is no escape. I just got my power back on at my house this morning and I definitely will be preparing for this tonight. During the height of the storm, something like 70% of St Louis City/County was without power.

Venture, maybe I heard wrong but I always understood that derechos were summer events that usually occurred in the Midwest and Northeast?

[venture]

Thank you for the update Venture! I have a question concerning the HRRR model. I know you have a link to it posted on the first page of this thread but am having trouble using it. I don't know what I'm looking at and what I should select. Yesterday you posted the HRRR and it looped to show convective development and motion, etc. What do I need to do to be able to look at the information myself today and going forward? I understand if you don't have time to do this today, but at some point a quick tutorial would be nice. I get lost trying to figure it out.

Sure...so the main page is: http://ruc.noaa.gov/hrrr/
Step 2) Click on 3km HRRR-CONUS hourly
Step 3) Under Domain select SC for South Central US
Step 4) Look at the time frames available. Usually if it isn't through Hour 06 yet, I'll just go up to Date and select the previous time.
Step 5) Depending on what you want to see you can click on the specific time or to loop all the times available you'll see a Check Mark under loop. You can click that to loop them all.

So for the simulated radar image you will go under the 3rd product called Composite Reflectivity and click the check mark under loop. That will provide the image I normally put. There are a ton of other products available for this model so enjoy.