possible severe outbreak in TX/OK on thursday?

[Ed Mahmoud]

New GFS, a tad more helicity and low level winds, somewhat less instability, which may or may not be affected by rainfall that has already occured, but taking it for what it is, better low level wind fields, but very limited instability below 650 mb, which would not be favorable for tornadoes.


.




As a cheat, looked at PPV AccuWx 'Rapid Update GFS', which, unlike the regular AccuWx PPV GFS, is in 6, not 3 hour increments shorter term. But the 0Z CAPE field shows that lower CAPE at DFW probably is precip induced, as higher CAPE surrounds, in the shape of a broken donut (hmmmm, donuts), 2000 J/Kg, surrounds DFW area, so maybe, just maybe, GFS is a bit more bullish tornado threat for DFW


Bed time approaches...

[CrazyC83]

The SPC definitely backed off on the tornado threat; it is only a MDT for hail...looks like no major outbreak at this point.

[Ed Mahmoud]

The SPC definitely backed off on the tornado threat; it is only a MDT for hail...looks like no major outbreak at this point.

12Z RUC has 25 knot low level winds near DFW late afternoon, vs 10 to 15 knot winds on last nights WRF. Now, I think RUC is quickest because RUC is simpler than the WRF, but if near surface winds are ten knots higher than predicted by 0Z WRF, then helicity values would be higher.

[gboudx]

Count me amongst those hoping to not see shear markers on the local TV radars tonight.

[Ed Mahmoud]

Pretty stout cap on the Fort Worth sounding, but if it warms into the low 80s, that cap should be breakable. A lot depends on how much sunshine DFW area gets. Models suggest two rounds possible for DFW area, although SPC doesn't think cap will break before late afternoon, one mid-afternoon, isolated cells, potentially tornadic, off the dry line or on other boundaries, and then the big show, more of a squall line, in the evening/overnight.

[Ed Mahmoud]

Some subsidence/clearing West of DFW in wake of first lead impulse. May aid daytime heating.



Low 70s now, but it is only about 10 am CDT, or closer to 9 am solar time.

[Ed Mahmoud]

SPC has issued a MD

MESOSCALE DISCUSSION 0537
NWS STORM PREDICTION CENTER NORMAN OK
1047 AM CDT THU APR 03 2008

AREAS AFFECTED...N-CNTRL/NERN TX INTO S-CNTRL/SERN OK

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 031547Z - 031645Z

TSTMS /INITIALLY ELEVATED/ MAY INCREASE IN COVERAGE AND INTENSITY
LATE THIS MORNING INTO AFTERNOON. INITIALLY LARGE HAIL WOULD BE THE
PRIMARY HAZARD. BUT AS STORMS BECOME MORE SURFACE-BASED...AN
ATTENDANT THREAT OF TORNADOES AND DAMAGING WINDS WILL CONCURRENTLY
INCREASE. THERE IS STILL SOME UNCERTAINTY AS TO WHETHER DEVELOPING
STORMS WILL BECOME SUSTAINED...NECESSITATING A WW THIS MORNING. IT
DOES APPEAR THAT A WW WILL LIKELY BE REQUIRED AT SOME POINT LATER
TODAY.

VISIBLE SATELLITE AND REGIONAL RADAR IMAGERY INDICATE DEEPENING
CUMULUS CONVECTION/EARLY TSTM DEVELOPMENT FROM THE METROPLEX WSWWD
TO NEAR ABI...PERHAPS IN RESPONSE TO A LOW AMPLITUDE PERTURBATION
MOVING ACROSS THE REGION. LATEST MESOANALYSIS INDICATES THAT THIS
ACTIVITY IS OCCURRING WITHIN SYSTEM WARM SECTOR WHICH IS DELINEATED
BY A RAPIDLY RETREATING WARM FRONT WHICH EXTENDED FROM JUST N OF THE
RED RIVER NW OF SPS TO JUST SW OF PRX AS OF 15Z. HOWEVER...BASED ON
THE 12Z OBSERVED SOUNDING FROM FWD AND RUC PROXIMITY SOUNDINGS IT
APPEARS THAT THE DEVELOPING STORMS MAY STILL BE SLIGHTLY ELEVATED
ABOVE A NEAR SURFACE STABLE LAYER.

GIVEN THE MOISTENING LOW-LEVELS AND PRESENCE OF VERY STEEP MIDLEVEL
LAPSE RATES OF AROUND 8.5 C/KM...ENVIRONMENT IS ALREADY MODERATELY
TO STRONGLY UNSTABLE FOR ELEVATED PARCELS WITH MUCAPES OF 2000-3000
J/KG. SHOULD TSTMS BECOME SUSTAINED...THE INITIAL SEVERE THREAT
WILL BE LARGE HAIL. WITH TIME THE BOUNDARY LAYER SHOULD WARM
SUFFICIENTLY SUCH THAT ANY ONGOING ACTIVITY WILL BECOME
PROGRESSIVELY MORE SURFACE-BASED. GIVEN 45-55 KT OF EFFECTIVE BULK
SHEARS AND MODERATELY STRONG LOW-LEVEL SHEAR...THE POTENTIAL WILL
EXIST FOR SUPERCELLS CAPABLE OF TORNADOES...DAMAGING WINDS IN
ADDITION TO THE LARGE HAIL.

..MEAD.. 04/03/2008

[Ed Mahmoud]

Anybody know who to find special (non-standard time) soundings?


I strongly suspect, as often happens when SPC has a 'Moderate Risk' area issued, that they will request the local NWS release a special 18Z sounding, and I'd love to know what that shows.

[tornado92]

Its looking more ominous as the day goes on. We may be about to see alot of tornado activity today.

[gboudx]

I've never heard of a "heatburst" before. I learnt something today.

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE FORT WORTH TX
1057 AM CDT THU APR 3 2008

.UPDATE...
POSITIVELY TILTED UPPER LEVEL TROUGH IS MOVING INTO THE ROCKIES
WITH THE BASE MOVING ACROSS SOUTHERN CALIFORNIA. SEVERAL EMBEDDED
SHORTWAVES ARE MOVING ACROSS THE SOUTHWESTERN UNITED STATES AND
TEXAS. ELEVATED SHOWERS AND THUNDERSTORMS HAVE NOW STARTED TO
DEVELOP ALONG INTERSTATE 20. WILL CONTINUE TO SEE SCATTERED
CONVECTION DEVELOP DURING THE DAY AS IMPULSES CROSS THE REGION
WITH THE BEST CHANCE ALONG AND NORTH OF INTERSTATE 20. HAVE
ADJUSTED POPS ACCORDINGLY. ON A SIDE NOTE...A HEATBURST OCCURRED
ABOUT AN HOUR AGO OVER THE ARLINGTON AREA PRODUCING 45-50 MPH
WINDS AND RESULTING IN RISING TEMPERATURES ACROSS THE SURROUNDING
AREAS. THE HEATBURST ARRIVED AT OUR OFFICE A FEW MINUTES AGO AND
THE TEMPERATURE ROSE ABOUT 3 DEGREES.

HAVE ADJUSTED TEMPERATURES UP IN MOST LOCATIONS FOR TODAY WITH
HEATING EXPECTED IN BETWEEN CLOUD BREAKS. EXPECT TEMPERATURES
RANGING FROM THE MID 80S OUT WEST TO THE UPPER 70S IN THE EAST. THE
IMPACT OF THE HEATBURST WAS ALSO A REASON FOR RAISING TEMPERATURES
IN THE METROPLEX INTO THE MID 80S. BREEZY CONDITIONS WILL CONTINUE
FOR THE DAY.

[CrazyC83]

Probably will be a tornado watch (not PDS) since part of it is in the 10% tornado area.

[Ed Mahmoud]

Probably will be a tornado watch (not PDS) since part of it is in the 10% tornado area.

SPC has issued a new MD suggesting a watch in an hour or so, while aviation update from NWS FWD suggests they think Metroplex will stay out of the action until late evening.

[Bunkertor]

TORNADO WATCH OUTLINE UPDATE FOR WT 153
NWS STORM PREDICTION CENTER NORMAN OK
205 PM CDT THU APR 3 2008

TORNADO WATCH 153 IS IN EFFECT UNTIL 900 PM CDT FOR THE
FOLLOWING LOCATIONS

TXC009-023-059-077-097-133-151-207-237-253-337-353-363-367-417-
429-441-447-485-487-497-503-040200-
/O.NEW.KWNS.TO.A.0153.080403T1905Z-080404T0200Z/

TX
. TEXAS COUNTIES INCLUDED ARE

ARCHER BAYLOR CALLAHAN
CLAY COOKE EASTLAND
FISHER HASKELL JACK
JONES MONTAGUE NOLAN
PALO PINTO PARKER SHACKELFORD
STEPHENS TAYLOR THROCKMORTON
WICHITA WILBARGER WISE
YOUNG

[CrazyC83]

SEL3

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 153
NWS STORM PREDICTION CENTER NORMAN OK
205 PM CDT THU APR 3 2008

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

CENTRAL OKLAHOMA
WESTERN NORTH TEXAS

EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 205 PM UNTIL
900 PM CDT.

TORNADOES...HAIL TO 4 INCHES IN DIAMETER...THUNDERSTORM WIND
GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE
AREAS.

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 70 STATUTE
MILES EAST AND WEST OF A LINE FROM 30 MILES NORTH OF CHANDLER
OKLAHOMA TO 25 MILES SOUTH SOUTHEAST OF ABILENE TEXAS. FOR A
COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE
UPDATE (WOUS64 KWNS WOU3).

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.

DISCUSSION...STRONG HEATING AND DESTABILIZATION WILL LEAD TO RAPID
SEVERE THUNDERSTORM DEVELOPMENT LATER THIS AFTERNOON ALONG SURFACE
DRYLINE FROM CENTRAL OK INTO NORTH TX. SUPERCELLS CAPABLE OF VERY
LARGE HAIL...DAMAGING WINDS...AND A FEW TORNADOES APPEAR LIKELY.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 4 INCHES. EXTREME TURBULENCE AND SURFACE
WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
500. MEAN STORM MOTION VECTOR 25030.


...HART

[CrazyC83]

They might want to throw a 60% hail risk in there...the potential exists for MEGA hail, possibly bigger than softballs.

[RL3AO]

They might want to throw a 60% hail risk in there...the potential exists for MEGA hail, possibly bigger than softballs.

I don't remember seeing anything at sixty percent since 04/07/06, where there were two 60% risks. But I'm sure there have been some 60% winds or hails since then.

[CrazyC83]

They might want to throw a 60% hail risk in there...the potential exists for MEGA hail, possibly bigger than softballs.

I don't remember seeing anything at sixty percent since 04/07/06, where there were two 60% risks. But I'm sure there have been some 60% winds or hails since then.

The last 60% hail was on 05/05/07 (the day after Greensburg), and that was hatched. The only 60% wind I am aware of was on 06/07/07 (it was also hatched), although I think that was a placeholder to preserve a high risk for that update with tornado uncertainty.

Hail cannot create a high risk by itself.

[CrazyC83]

Virtually unchanged from last update:

SPC AC 032000

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0300 PM CDT THU APR 03 2008

VALID 032000Z - 041200Z

...THERE IS A MDT RISK OF SVR TSTMS FROM PARTS OF N CNTRL THROUGH
NERN TX INTO S CNTRL AND SERN OK THROUGH WRN AR...

...THERE IS A SLGT RISK OF SVR TSTMS FROM SWRN TX THROUGH THE LOWER
MS VALLEY AND PARTS OF THE TN AND LOWER OH VALLEY...

...SWRN TX...CNTRL AND ERN OK THROUGH PARTS OF THE LOWER OH AND TN
VALLEYS...

LATE THIS AFTERNOON A DRYLINE EXTENDS FROM WRN OK SWWD THROUGH SWRN
TX. WARM FRONT STRETCHES FROM A SURFACE LOW NEAR ENID OK SE THROUGH
NERN TX...SRN AR INTO NRN MS AND NRN AL...THEN SEWD INTO SW GA. COLD
FRONT EXTENDS FROM THE SURFACE LOW SWWD THROUGH NWRN OK INTO THE TX
PANHANDLE.

WARM SECTOR IS DESTABILIZING FROM SWRN THROUGH N CNTRL TX INTO S
CNTRL AND SERN OK. THE WARM FRONT IS EXPECTED TO LIFT FARTHER NWD
THROUGH ERN OK AND AT LEAST INTO CNTRL AR THIS EVENING. LOW TO MID
60S DEWPOINTS ARE ADVECTING NWD THROUGH WARM SECTOR BENEATH 7-8 C/KM
700-500 MB LAPSE RATES. LOW CLOUDS HAVE BEGUN TO MIX OUT IN VICINITY
OF AND JUST EAST OF DRYLINE CONTRIBUTING WEAKENING CONVECTIVE
INHIBITION AND 1500 TO 2000 J/KG MLCAPE. STORMS ARE INCREASING
WITHIN ZONE OF LOW LEVEL CONFLUENCE AND WARM ADVECTION FROM NWRN TX
THROUGH CNTRL AND ERN OK. MUCH OF THE THIS ACTIVITY STILL APPEARS
SOMEWHAT ELEVATED WITH INITIAL THREAT BEING LARGE HAIL. HOWEVER...AS
THE BOUNDARY LAYER CONTINUES TO DESTABILIZE THE STORMS WILL LIKELY
BECOME SURFACE BASED. FAVORABLE BULK SHEAR FROM 40-50 KT ALONG WITH
STEEP LAPSE RATES AND COLD MID LEVEL PROFILES WILL SUPPORT THREAT OF
VERY LARGE HAIL WITH SUPERCELL STRUCTURES...ESPECIALLY AS STORMS
BECOME ROOTED IN THE BOUNDARY LAYER LATER THIS AFTERNOON AND
EVENING.

THE LOW LEVEL JET WILL GRADUALLY SHIFT EAST INTO NERN TX...SERN OK
AND THE LOWER MS VALLEY WITH WEAKENING AND VEERING LOW LEVEL FLOW
FARTHER WEST NEAR THE DRYLINE. LARGEST LOW LEVEL HODOGRAPHS AND
TORNADO POTENTIAL THEREFORE APPEARS GREATEST FROM N CNTRL AND NERN
TX...SERN OK INTO PARTS OF AR LATER THIS AFTERNOON AND EVENING ALONG
AND SOUTH OF RETREATING WARM FRONT. LARGE HAIL WILL REMAIN THE
PRIMARY THREAT WITH STORMS DEVELOPING FARTHER NORTH IN COOL SECTOR
NORTH OF WARM FRONT.

OTHER STORMS WILL LIKELY DEVELOP FARTHER SW ALONG THE DRYLINE ACROSS
WRN AND SWRN TX WITHIN THE NEXT SEVERAL HOURS. SUPERCELLS WITH VERY
LARGE HAIL WILL BE POSSIBLE WITH THIS ACTIVITY...THOUGH AND ISOLATED
TORNADO OR TWO CANNOT BE RULED OUT.

THE COLD FRONT WILL ADVANCE SOUTH THROUGH OK...NRN TX AND INTO NRN
AR OVERNIGHT. ADDITIONAL STORMS MAY DEVELOP AND ORGANIZE INTO LINES
WITH EMBEDDED ORGANIZED STORM STRUCTURES ALONG THE FRONT WITH A
THREAT FOR MAINLY DAMAGING WIND AND LARGE HAIL THE MAIN THREATS.

..DIAL.. 04/03/2008

CLICK TO GET WUUS01 PTSDY1 PRODUCT

NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z

[RL3AO]

40%/20% for tornadoes.

[CrazyC83]

SEVERE THUNDERSTORM WARNING
OKC067-TXC009-077-485-032200-
/O.NEW.KOUN.SV.W.0191.080403T2109Z-080403T2200Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE NORMAN OK
409 PM CDT THU APR 3 2008

THE NATIONAL WEATHER SERVICE IN NORMAN HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
NORTHEASTERN ARCHER COUNTY IN NORTHERN TEXAS...
CLAY COUNTY IN NORTHERN TEXAS...
EXTREME SOUTHEASTERN WICHITA COUNTY IN NORTHERN TEXAS...
SOUTHWESTERN JEFFERSON COUNTY IN SOUTHERN OKLAHOMA...

* UNTIL 500 PM CDT

* AT 409 PM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
SEVERE THUNDERSTORM NEAR CENTRAL LAKE ARROWHEAD...MOVING EAST AT 40
MPH. HAIL UP TO THE SIZE OF SOFTBALLS AND WINDS OF 65 MPH ARE
LIKELY.

* LOCATIONS IN THE WARNING INCLUDE BLUEGROVE...BYERS...EXTREME
SOUTHEASTERN WICHITA FALLS...HENRIETTA...JOLLY...LAKE ARROWHEAD...
PETROLIA AND TERRAL.

SEVERE THUNDERSTORMS CAN PRODUCE TORNADOES WITH NO ADVANCE WARNING.
MOVE IMMEDIATELY TO A STORM SHELTER... BASEMENT OR STURDY BUILDING IF
A TORNADO IS SIGHTED.

LAT...LON 3417 9807 3386 9787 3385 9790 3387 9792
3387 9796 3364 9797 3363 9842 3379 9854
TIME...MOT...LOC 2109Z 250DEG 36KT 3373 9832

$$


MAXWELL