Alert archive / Texas / Mesoscale Discussions in 2012

Mesoscale Discussion 2131

December 4, 201226 counties in Texas

The Storm Prediction Center issued this mesoscale discussion at Dec 4, 2012, 1:08 PM CST for 26 counties in Texas. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued
Dec 4, 2012, 1:08 PM CST (19:08 UTC)
Expired
Dec 4, 2012, 3:15 PM CST
In force
2 hr
Issued by
the Storm Prediction Center
Chance of a watch
40%
All 26 counties

Aransas County, TX, Austin County, TX, Bee County, TX, Brazoria County, TX, Brooks County, TX, Calhoun County, TX, Colorado County, TX, DeWitt County, TX, Duval County, TX, Fort Bend County, TX, Galveston County, TX, Goliad County, TX, Harris County, TX, Jackson County, TX, Jim Wells County, TX, Karnes County, TX, Kleberg County, TX, Lavaca County, TX, Live Oak County, TX, Matagorda County, TX, McMullen County, TX, Nueces County, TX, Refugio County, TX, San Patricio County, TX, Victoria County, TX, Wharton County, TX

The radar

The Corpus Christi radar (KCRP), 70 km from the middle of the area, began a volume at 19:11 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

Corpus Christi, TX (KCRP), launched 12:00Z, 7.1 hours before the alert went out and 68 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, Corpus Christi, TX at 12:00Z on 2012-12-04Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1399 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, Corpus Christi, TX at 12:00Z on 2012-12-04The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 76 square meters per square second.193958Sfc1 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
1399 J/kg
Mixed-layer CIN
-90 J/kg
Mixed-layer LCL
715 m above ground
0-6 km bulk shear
25 kt
0-1 km storm-relative helicity
76 m²/s²
0-3 km storm-relative helicity
68 m²/s²
Significant tornado parameter
0.2
Supercell composite
2.6

Open this sounding in Storm Lab

The text

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

217 
ACUS11 KWNS 041909
SWOMCD
SPC MCD 041908
TXZ000-042115-

MESOSCALE DISCUSSION 2131
NWS STORM PREDICTION CENTER NORMAN OK
0108 PM CST TUE DEC 04 2012

AREAS AFFECTED...TX COASTAL PLAIN

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 041908Z - 042115Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...A SMALL SEVERE TSTM WATCH MAY BE CONSIDERED FOR PARTS OF
THE TX COASTAL PLAIN THIS AFTERNOON-EVENING.  ISOLD LARGE HAIL AND A
FEW INSTANCES OF STRONG-SEVERE WIND GUSTS ARE POSSIBLE THRU THE
EARLY EVENING.

DISCUSSION...TRENDS IN VISIBLE SATELLITE IMAGERY SHOW A SWELLING CU
FIELD INVOF A PRE-FRONTAL WINDSHIFT AND OVER A WARM SECTOR LOCATED
OVER THE TX COASTAL PLAIN.  SURFACE TEMPS HAVE WARMED INTO THE LOWER
80S AMIDST AN ADEQUATELY MOIST/DESTABILIZING AIRMASS.  A MID-LEVEL
SPEED MAX IS CONTINUING TO APPROACH THE REGION FROM THE CONCHO RIVER
VALLEY/EDWARDS PLATEAU REGION.  UPWARD VERTICAL MOTION ASSOCIATED
WITH THE UPPER FEATURE...COMBINED WITH WEAK LOW LEVEL CONFLUENCE
ALONG THE PREFRONTAL BOUNDARY...AND DIABATIC HEATING WILL ACT TO
FURTHER WEAKEN THE CAP SAMPLED BY THE 12Z CRP RAOB.  THE CAP HAS
ALREADY ERODED FROM MATAGORDA BAY NEWD TO THE SABINE RIVER...WITH
SCTD STORMS /OCCASIONAL PULSATING SEVERE UPDRAFT/ EXPECTED TO LEAD
TO SUBSTANTIAL CONVECTIVE OVERTURNING OVER THE NEXT FEW
HRS...THEREBY LESSENING THE SEVERE RISK IN THIS REGION.  FARTHER
SSW...MORE SPARSE CONVECTIVE COVERAGE --LIKELY DELAYED UNTIL
MID-LATE AFTERNOON-- IS EXPECTED.  UPWARDS OF 40 KT DEEP SHEAR AND A
MODERATELY UNSTABLE AIRMASS /1500 J/KG MLCAPE/ WILL SUPPORT
ORGANIZED STORM STRUCTURES CAPABLE OF ISOLD LARGE HAIL/DMGG WIND
GUSTS.

..SMITH/MEAD.. 12/04/2012

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

ATTN...WFO...HGX...CRP...EWX...BRO...

LAT...LON   27199742 26789801 27619907 28629874 29919674 30099507
            29359469 28019688 27199742

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Dec 4, 11:09 AM CSTMesoscale DiscussionSPCAngelina, Chambers, Hardin, Jasper, Jefferson, Liberty and 8 more96 min

Nearby

Mesoscale Discussions in Texas, 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.