Oklahoma Severe Weather Discussion - April 2011

[venture]

Side note, the chat room at chatokc.com will be staffed for the rest of the day to track both severe weather and the fires.

Also HRRR model's 15Z run giving initiation around 4PM in the following scenario:



http://rapidrefresh.noaa.gov/hrrrcon...Apr+2011+-+15Z

[BG918]

Looking at some data it suggests the upper level winds are favorable for tornadoes in eastern OK into southeast KS. Venture, you seem to have access to much more data - where do you think the areas most favorable for tornado development will be? I think you are right that we will see cumulus development begin around 3-4 pm over the OKC metro and points north and south with movement to the east-northeast. Ponca City, Stillwater, Stroud, Seminole, etc. could be affected as these storms develop and quickly become severe and/or tornadic. Later around 5-6 the Tulsa metro could see severe weather too with everything becoming more linear into the late evening in far eastern OK moving into western AR.

[venture]

Southeast OK and Northern Texas are really getting my attention right now with the latest HRRR. Northern OK looks more like a squall with embedded supercells. If I was chasing today, I would probably hang tight and plan to go south and east. Not to say there won't be any in NE OK or KS. There will, I just see a more classic arrangement of cells south. I won't be shocked to see the MDT risk get pushed closer to the Metroplex in the next update. Some think SPC will go High in the next update, but not sure if it really warrants that.

[Charlie40]

Southeast OK and Northern Texas are really getting my attention right now with the latest HRRR. Northern OK looks more like a squall with embedded supercells. If I was chasing today, I would probably hang tight and plan to go south and east. Not to say there won't be any in NE OK or KS. There will, I just see a more classic arrangement of cells south. I won't be shocked to see the MDT risk get pushed closer to the Metroplex in the next update. Some think SPC will go High in the next update, but not sure if it really warrants that.

Venture, In your comment about Metroplex are you referring to the OKC metro area and point north and south from there?

[venture]

Nope, sorry about that. Metroplex = DFW. :-) I expect most of the central OKC metro area pulled out of the outlook at the next update. Dryline is just moving east too fast at this point - currently going through western Oklahoma county right now.

[OKCisOK4me]

Good, I hate the thought of baseball hail hitting my car.

[venture]

From Norman...

.REGIONAL WEATHER DISCUSSION...
AROUND 1 PM..SURFACE OBSERVATIONS INDICATED THAT A DRYLINE EXTENDED
ALONG AND JUST WEST OF THE INTERSTATE 35 CORRIDOR. BEHIND THE
DRYLINE...DEWPOINTS HAVE DROPPED INTO THE 30S AND 40S...WITH UPPER
50S AND LOW 60S AHEAD OF THE DRYLINE.

THUNDERSTORMS WILL BEGIN TO DEVELOP AS THE DRYLINE CONTINUES TO PUSH
EASTWARD THROUGHOUT THE AFTERNOON AS A SURFACE LOW ACROSS SOUTHERN
KANSAS INTENSIFIES. THUNDERSTORMS SHOULD BEGIN TO DEVELOP AROUND 3
PM. SUFFICIENT WIND SHEAR AND INSTABILITY WILL SUPPORT STRONG TO
SEVERE THUNDERSTORMS CAPABLE OF PRODUCING LARGE HAIL..DAMAGING
WINDS...AND ISOLATED TORNADOES MAINLY ALONG AND EAST OF A LINE FROM
CUSHING TO ADA TO DURANT. BEHIND THE DRYLINE...STRONG WESTERLY WINDS
WILL RESULT IN AND ELEVATED WILDFIRE POTENTIAL.

[venture]

New MCD - Chat is live at www.chatokc.com



MESOSCALE DISCUSSION 0425
NWS STORM PREDICTION CENTER NORMAN OK
0133 PM CDT THU APR 14 2011

AREAS AFFECTED...PORTIONS CENTRAL/N-CENTRAL/NE TX...ERN OK.

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY

VALID 141833Z - 142100Z

EXPECT DEVELOPMENT OF SEVERAL POTENTIALLY LONG-LIVED SUPERCELLS ALONG/AHEAD OF DRYLINE BEGINNING IN 20-22Z TIME FRAME...COVERAGE INCREASING THROUGH REMAINDER AFTERNOON/EVENING AS ACTIVITY MOVES EWD TO NEWD. DAMAGING HAIL IS LIKELY...SOME EXCEEDING 3 INCHES DIAMETER. THREAT WILL INCREASE FOR TORNADOES AS TSTMS MATURE AND MOVE INTO PROGRESSIVELY MORE MOIST/HIGH-SRH AIR MASS...WITH TIME AND EWD EXTENT.

18Z SFC MESOANALYSIS SHOWS DRYLINE JUST E OF US-81 CORRIDOR IN OK THEN SWWD ACROSS JACK COUNTY TX...WHERE VIS IMAGERY INDICATES CONCENTRATION OF DEEP CU. DRYLINE SHOULD CONTINUE TO MIX/ADVECT EWD ACROSS I-35 FROM PVJ AREA NWD...BEFORE DECELERATING AROUND 23Z. TX DRYLINE SEGMENT SHOULD MOVE EWD TO JUST W OF DFW METROPLEX...NEAR PRESENT LOCATION OF CONFLUENCE LINE THAT EXTENDS NNEWD FROM HILL COUNTRY. DRYLINE MAY SHARPEN FURTHER...GIVEN COMBINATION OF 1. CONTINUING MOST ADVECTION TO ITS E...
2. BACKING 850-MB WINDS EVIDENT PAST COUPLE HOURS IN CENTRAL OK VWP/PROFILER DATA...AND 3. GEOMETRY OF PRESSURE FALLS OVER KS/OK THAT MAY KEEP SLGT ELY COMPONENT TO SFC FLOW IN MOIST SECTOR IN CORRIDOR FROM OSAGE COUNTY SWD TO DUA AREA THROUGH 00Z.

EXPECT CONTINUED STG SFC HEATING...DEW POINTS RANGING FROM UPPER 50S F IN NRN OK TO MID 60S FROM ADM-ATOKA AREA SWD ACROSS RED RIVER...AND STEEPENING LAPSE RATES ALOFT. THIS WILL BOOST MLCAPE TO 2000-3000 J/KG RANGE OVER PORTIONS N TX AND SERN OK BASED ON MODIFIED 18Z FWD/OUN RAOBS...AND 1500-2000 J/KG NEAR OK/KS BORDER.
MEANWHILE...DEEP-LAYER SHEAR WILL STRENGTHEN...AS ALREADY EVIDENT WITH LOWERING OF 50-KT MIDLEVEL ISOTACH AT TCU PROFILER. EFFECTIVE SHEAR SHOULD INCREASE TO 50-60 KT. HODOGRAPH SIZE...NOW INDICATING SOME WEAKNESSES AROUND 1-3 KM AGL...WILL INCREASE MARKEDLY DURING LATE AFTERNOON AND EARLY EVENING OVER ERN OK...BECOMING POTENTIALLY FAVORABLE FOR SIGNIFICANT TORNADO PRODUCTION. STG ORTHOGONAL COMPONENT OF MEAN WIND AND DEEP-SHEAR VECTORS...RELATIVE TO DRYLINE...INDICATES STORMS CAN REMAIN DISCRETE FOR AT LEAST A FEW HOURS AFTER INITIATION. COVERAGE SWD INTO CENTRAL TX SHOULD BE MORE ISOLATED/CONDITIONAL.

SRN END OF KS CONVECTIVE ARC REGIME -- SEE MESOSCALE DISCUSSION 424 FOR DETAILS -- MAY BACKBUILD INTO PORTIONS N-CENTRAL/NERN OK AFTER ABOUT 21Z AS WELL.

..EDWARDS.. 04/14/2011

[venture]

PDS Tornado Watch incoming.

[Roadhawg]

Looks like it might be safe to leave my top down on the jeep... not my top but the jeeps

[venture]

Ww 135 tornado ok tx 141930z - 150300z
axis..80 statute miles east and west of line..
15nne bvo/bartlesville ok/ - 40sse gyi/sherman tx/ ..aviation coords.. 70nm e/w /36wsw osw - 37ene dfw/ hail surface and aloft..4 inches. Wind gusts..70 knots.
Max tops to 550. Mean storm motion vector 24035.

[PennyQuilts]

Sigh. I wish we'd get some rain...

[Roadhawg]

Sigh. I wish we'd get some rain...

me too

[jn1780]

Does the fact were so dry cause the dryline to move east faster?

[venture]

Full Watch Discussion...



URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 135
NWS STORM PREDICTION CENTER NORMAN OK
230 PM CDT THU APR 14 2011

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

MUCH OF THE EASTERN HALF OF OKLAHOMA
PARTS OF NORTH CENTRAL/NORTHEASTERN TEXAS

EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 230 PM UNTIL
1000 PM CDT.

...THIS IS A PARTICULARLY DANGEROUS SITUATION...

NUMEROUS TORNADOES
INTENSE TORNADOES LIKELY
WIDESPREAD DAMAGING WINDS
ISOLATED WIND GUSTS TO 80 MPH POSSIBLE
WIDESPREAD LARGE HAIL
HAIL TO 4.0 INCHES IN DIAMETER LIKELY

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 80 STATUTE
MILES EAST AND WEST OF A LINE FROM 15 MILES NORTH NORTHEAST OF
BARTLESVILLE OKLAHOMA TO 40 MILES SOUTH SOUTHEAST OF SHERMAN
TEXAS. FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED
WATCH OUTLINE UPDATE (WOUS64 KWNS WOU5).

REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR
TORNADOES AND 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.

OTHER WATCH INFORMATION...CONTINUE...WW 134...

DISCUSSION...DRY LINE LOCATED VICINITY I-35 CORRIDOR WITH THE AIR
MASS NOW VERY UNSTABLE EWD ACROSS OK. WITH LITTLE REMAINING
CINH...SEVERE THUNDERSTORMS WILL DEVELOP RAPIDLY OFF THE DRY LINE
AND MOVE THRU A VERY FAVORABLE ENVIRONMENT FOR SUPERCELLS. INITIALLY
VERY LARGE HAIL WILL BE THE RISK GIVEN THE STEEP LAPSE RATES AND
DEEP LAYER SHEAR. AS THE STRONG UPPER JET MAX APPROACHES TORNADIC
SUPERCELLS WILL BECOME MORE LIKELY BY LATER THIS AFTERNOON/EVENING
WITH POTENTIAL FOR LONG LIVED SUPERCELLS AND STRONG TORNADOES. DRY
LINE VERY LIKELY WILL MOVE LITTLE EWD FROM CURRENT POSITION WITH
POTENTIAL FOR SEVERE STORMS DEVELOPING ON W EDGE OF WATCH INTO THE
EVENING HOURS.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 4 INCHES. EXTREME TURBULENCE AND SURFACE
WIND GUSTS TO 70 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
550. MEAN STORM MOTION VECTOR 24035.


TORNADO WATCH PROBABILITIES FOR WT 0135
NWS STORM PREDICTION CENTER NORMAN OK
0232 PM CDT THU APR 14 2011

WT 0135 PDS
PROBABILITY TABLE:
PROB OF 2 OR MORE TORNADOES : 90%
PROB OF 1 OR MORE STRONG /F2-F5/ TORNADOES : 60%
PROB OF 10 OR MORE SEVERE WIND EVENTS : 80%
PROB OF 1 OR MORE WIND EVENTS >= 65 KNOTS : 50%
PROB OF 10 OR MORE SEVERE HAIL EVENTS : >95%
PROB OF 1 OR MORE HAIL EVENTS >= 2 INCHES : >95%
PROB OF 6 OR MORE COMBINED SEVERE HAIL/WIND EVENTS : >95%

&&
ATTRIBUTE TABLE:
MAX HAIL /INCHES/ : 4.0
MAX WIND GUSTS SURFACE /KNOTS/ : 70
MAX TOPS /X 100 FEET/ : 550
MEAN STORM MOTION VECTOR /DEGREES AND KNOTS/ : 24035
PARTICULARLY DANGEROUS SITUATION : YES

[Jesseda]

I am at work right now looking out my window ( im at the will rogers airport) im lookingsoutheast towards moore, the clouds are growing tall and long..i would say from southeast okc all the way to newcastle area

[venture]

Switching to monitor the live chat. Radar is also active now as well.

[BG918]

Just as predicted storms firing on the dryline in Pawnee, Lincoln and Carter counties. Each one has a high probability of becoming severe very quickly.

[Bunty]

Severe thunderstorm now 10 miles east-northest of Stillwater.

[Achilleslastand]

Jeesh.....Just missed the okc metro area again. Im going outside and do a raindance.

[Uncle Slayton]

This bites. So, Norman is out of the game for tornadic activity this early?

[venture]

Making an update. The dryline has stalled as the models this morning were hinting at. It is currently runnign from Stillwater to Norman to Lindsay and south from there. SPC is thinking it may start retreating a bit to the west before the cold front arrives later.



MESOSCALE DISCUSSION 0426
NWS STORM PREDICTION CENTER NORMAN OK
0521 PM CDT THU APR 14 2011

AREAS AFFECTED...ERN HALF OF OK / PARTS OF N-CNTRL AND NERN TX

CONCERNING...TORNADO WATCH 135...

VALID 142221Z - 142315Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 135 CONTINUES.

A DRYLINE EXTENDS FROM THE KS/OK BORDER 20 NNE OF PNC TO 25 SE OF
OKC TO THE RED RIVER 25 WSW OF ADM AND FARTHER S-SW INTO N-CNTRL TX.
THE ARCING LINE OF SEMI-DISCRETE SUPERCELLS THAT INITIATED ALONG THE
DRYLINE CONTINUES TO SHIFT EWD TOWARD ERN OK...AND WILL CONTINUE TO
DO SO DURING THE NEXT FEW HOURS GIVEN EFFECTIVE BULK SHEAR VECTORS
ORTHOGONAL TO THE DRYLINE WITH MAGNITUDES OF 45 TO 60 KT. THIS
DEGREE OF DEEP-LAYER WIND SHEAR WILL MAINTAIN THE SUPERCELL THREAT
AS STORMS APPROACH THE TULSA AND MCALESTER AREAS THROUGH 2330Z WHILE
TRAVERSING MLCAPE VALUES OF 2000-2500 J/KG. EFFECTIVE SRH VALUES OF
100-200 M2/S2 SUPPORT A TORNADO THREAT ANY SUSTAINED SUPERCELLS.
THIS THREAT WILL FURTHER INCREASE INTO THE EVENING...ALONG WITH THE
THREAT FOR STRONG TORNADOES...AS EFFECTIVE SRH VALUES INCREASE PER
THE LATEST RUC GUIDANCE. THE GREATEST THREAT FOR STRONG TORNADOES
WILL BE ACROSS SERN OK INTO FAR NERN TX THROUGH 00Z...WHERE SFC-3 KM
CAPE VALUES FROM 100-150 J/KG WILL PROVIDE ENHANCED LOW-LEVEL
BUOYANCY TO THE RELATIVELY MORE DISCRETE CONVECTION /COMPARED TO
FARTHER NORTH/.

FARTHER SOUTH ALONG THE DRYLINE...CONVECTION IS INITIATING ACROSS
PORTIONS OF N-CNTRL TX TO THE NORTH OF THE DFW AREA. GIVEN THE
DEGREE OF POTENTIAL INSTABILITY AND DEEP-LAYER WIND SHEAR...THESE
STORMS COULD EVENTUALLY POSE A THREAT FOR LARGE HAIL. THERE WILL
ALSO BE A THREAT FOR A TORNADO GIVEN THE VEERING WIND PROFILE
EVIDENT IN THE SFC-2-KM LAYER PER THE NEARBY FORT WORTH VWP.
THUS...THE TORNADO WATCH MAY NEED TO BE EXTENDED FARTHER SOUTH BY
ONE TIER OF COUNTIES IN NERN TX IF STORMS FURTHER INTENSIFY.

LATEST RUC GUIDANCE IS SUGGESTING THAT THE DRYLINE WILL REMAIN
STATIONARY INTO EARLY EVENING ACROSS CNTRL/SRN OK...AND POTENTIALLY
BE NUDGED WWD A BIT. THIS MAY SERVE TO FOCUS ANOTHER ATTEMPT AT
CONVECTIVE INITIATION AFTER 00Z AS AN AREA OF DEEP-LAYER ASCENT
APPROACHES. THIS IS SUPPORTED BY THE LATEST EXPERIMENTAL HRRR
GUIDANCE...AND THESE TRENDS WILL CONTINUE TO BE MONITORED FOR A
PERSISTENT SEVERE THREAT INTO THE EVENING ACROSS THE WRN PORTIONS OF
THE WATCH.

[BG918]

This bites. So, Norman is out of the game for tornadic activity this early?

You say that like it's a bad thing?

[kevinpate]

Sigh. I wish we'd get some rain...

I agree. Not so much for us. We've seen rain. But for the wee ones ....



(have long liked that line)

[jn1780]

Would have been nice if everything started 50 miles further west. Close enough to get good rain, but still move east before producing any tornadoes.