Alert archive / Texas / Mesoscale Discussions in 2012

Mesoscale Discussion 699

May 4, 2012Cotton County, Tillman County, Oklahoma; 18 counties in Texas

The Storm Prediction Center issued this mesoscale discussion at May 4, 2012, 5:30 PM CDT for Cotton County, Tillman County, Oklahoma; 18 counties in Texas. It was in force for 60 min.

The area

The outline as issued.

The facts

Issued
May 4, 2012, 5:30 PM CDT (22:30 UTC)
Expired
May 4, 2012, 6:30 PM CDT
In force
60 min
Issued by
the Storm Prediction Center

Counties Cotton County, OK, Tillman County, OK, Archer County, TX, Baylor County, TX, Callahan County, TX, Clay County, TX, Coke County, TX, Eastland County, TX, Irion County, TX, Jack County, TX, Palo Pinto County, TX, Parker County, TX, Runnels County, TX, Shackelford County, TX, Stephens County, TX, Taylor County, TX, Throckmorton County, TX, Tom Green County, TX, Wichita County, TX, Young County, TX

The radar

The Dyess AFB radar (KDYX), 30 km from the middle of the area, began a volume at 22:33 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The nearest sounding before it

Fort Worth, TX (KFWD), launched 12:00Z, 10.5 hours before the alert went out and 206 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-pSkew-T log-p diagram, Fort Worth, TX at 12:00Z on 2012-05-04Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 2222 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Fort Worth, TX at 12:00Z on 2012-05-04The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 86 square meters per square second.19395878Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.
Mixed-layer CAPE
2222 J/kg
Mixed-layer CIN
-258 J/kg
Mixed-layer LCL
793 m above ground
0-6 km bulk shear
19 kt
0-1 km storm-relative helicity
86 m²/s²
0-3 km storm-relative helicity
13 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

291 
ACUS11 KWNS 042231
SWOMCD
SPC MCD 042230
TXZ000-OKZ000-042330-

MESOSCALE DISCUSSION 0699
NWS STORM PREDICTION CENTER NORMAN OK
0530 PM CDT FRI MAY 04 2012

AREAS AFFECTED...SWRN OK INTO SWRN TX

CONCERNING...SEVERE THUNDERSTORM WATCH 240...

VALID 042230Z - 042330Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 240
CONTINUES.

SUMMARY...SEVERE THUNDERSTORMS CAPABLE OF DMGG WINDS AND LARGE HAIL
ARE INCREASING IN COVERAGE ALONG THE DRYLINE. THESE STORMS ARE
SLOWLY PROGRESSING EWD AT ABOUT 15 KTS.

DISCUSSION...THE SRN EDGE OF AN UPPER WAVE NOTED ON 22Z WV IMAGERY
FROM SERN KS...CNTRL OK INTO N CNTRL TX HAS LIKELY PROVIDED SUBTLE
FORCING FOR ASCENT...ALLOWING SCATTERED THUNDERSTORMS TO DEVELOP
ALONG THE DRYLINE. AMPLE SURFACE HEATING HAS CONTRIBUTED TO
TEMPERATURES NEAR 100 SURROUNDING THE DRYLINE...WHICH HAS BEEN MORE
THAN SUFFICIENT TO ERODE ANY REMAINING CONVECTIVE INHIBITION. AS
SUCH...STORMS HAVE GRADUALLY BEEN INCREASING IN COVERAGE. DESPITE
THE SLOW FORWARD MOTION /MEASURED AT ABOUT 15 KTS/...THESE AREAS OF
CONVECTION WILL GRADUALLY PROGRESS INTO A MORE UNSTABLE AIR
MASS...POSSIBLY SUPPORTING SEMI-ORGANIZED CLUSTERS AND SMALL BOWING
SEGMENTS GIVEN MODEST FLOW ALOFT...SHOULD A FEW ORGANIZED COLD POOLS
DEVELOP. HOWEVER...THESE THUNDERSTORMS WILL ALSO BE PROGRESSING AWAY
FROM MORE FAVORABLE SURFACE CONVERGENCE...WHICH MAY LEAD TO A
WEAKENING OF A FEW STORMS AS WELL. A FEW HI-RES MODELS INDICATE
POTENTIAL DEVELOPMENT INVOF AN AREA OF CU EXTENDING FROM NEAR ACT
NWWD TO MWL. HOWEVER...SURFACE OBSERVATIONS SHOW LITTLE
CONFLUENCE/CONVERGENCE THAT MAY FOSTER GREATER UPWARD GROWTH...SO
CONFIDENCE IN THIS ADDITIONAL DEVELOPMENT REMAINS LOW.

..HURLBUT.. 05/04/2012

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...FWD...OUN...SJT...MAF...

LAT...LON   34419841 33779782 32789779 32449857 31989941 31400021
            30980128 31050190 31660111 32350018 33409933 34649898
            34419841

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
May 4, 2:50 PM CDTMesoscale DiscussionSPCComanche, Cotton, Greer, Harmon, Jackson, Tillman85 min
May 4, 3:49 PM CDTSevere Thunderstorm WatchSPCCarter, Comanche, Cotton, Jackson, Jefferson, Love and 3 more7 hr

Nearby

Mesoscale Discussions in Texas, 2012Mesoscale Discussions in Oklahoma, 2012Every mesoscale discussion in 2012

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.