Alert archive / Texas / Mesoscale Discussions in 2012

Mesoscale Discussion 2124

November 26, 201229 counties in Texas

The Storm Prediction Center issued this mesoscale discussion at Nov 26, 2012, 5:08 PM CST for 29 counties in Texas. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued
Nov 26, 2012, 5:08 PM CST (23:08 UTC)
Expired
Nov 26, 2012, 7:15 PM CST
In force
2 hr
Issued by
the Storm Prediction Center
Chance of a watch
40%
All 29 counties

Austin County, TX, Bastrop County, TX, Brazos County, TX, Burleson County, TX, Caldwell County, TX, Chambers County, TX, Colorado County, TX, Fayette County, TX, Fort Bend County, TX, Gonzales County, TX, Grimes County, TX, Hardin County, TX, Harris County, TX, Hays County, TX, Jefferson County, TX, Lavaca County, TX, Lee County, TX, Liberty County, TX, Madison County, TX, Milam County, TX, Montgomery County, TX, Robertson County, TX, San Jacinto County, TX, Travis County, TX, Walker County, TX, Waller County, TX, Washington County, TX, Wharton County, TX, Williamson County, TX

The radar

The Houston radar (KHGX), 113 km from the middle of the area, began a volume at 23:08 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

Lake Charles Mun, LA (KLCH), launched 12:00Z, 11.1 hours before the alert went out and 265 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, Lake Charles Mun, LA at 12:00Z on 2012-11-26Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1074 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, Lake Charles Mun, LA at 12:00Z on 2012-11-26The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 207 square meters per square second.1939587897Sfc1 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
1074 J/kg
Mixed-layer CIN
-9 J/kg
Mixed-layer LCL
505 m above ground
0-6 km bulk shear
32 kt
0-1 km storm-relative helicity
207 m²/s²
0-3 km storm-relative helicity
230 m²/s²
Significant tornado parameter
0.8
Supercell composite
5.5

Open this sounding in Storm Lab

The text

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

661 
ACUS11 KWNS 262308
SWOMCD
SPC MCD 262308 
LAZ000-TXZ000-270115-

MESOSCALE DISCUSSION 2124
NWS STORM PREDICTION CENTER NORMAN OK
0508 PM CST MON NOV 26 2012

AREAS AFFECTED...PORTIONS OF CNTRL/SERN TX

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

VALID 262308Z - 270115Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...ISOLATED SVR STORMS WITH SVR HAIL AND POSSIBLY SVR WINDS
MAY BE OF CONCERN LATE THIS AFTERNOON INTO THE EVENING...AND THE
ISSUANCE OF A WW IS POSSIBLE.

DISCUSSION...A COLD FRONT EXTENDS FROM THE ARKLATEX SWWD ACROSS THE
EDWARDS PLATEAU AND FARTHER W INTO THE TRANS-PECOS REGION. A FRONTAL
INFLECTION NOTED E OF JUNCTION TX APPEARS TO BE THE FOCUS FOR A
SMALL...BUT PERSISTENT...AREA OF CONVECTION. RECENT STORM
DEVELOPMENT IS NOTED IN CNTRL TX ALONG A PREFRONTAL TROUGH THAT
DELINEATES THE WRN EDGE OF RICHER GULF MOISTURE AND EXTENDS FROM
JUST NORTH OF SHREVEPORT LA TO NORTH OF AUSTIN. DURING THE NEXT FEW
HOURS...STORM COVERAGE WILL LIKELY INCREASE ALONG THE PREFRONTAL
TROUGH...WEST OF WHICH A DEEPER BOUNDARY LAYER/STEEP LOW-LEVEL LAPSE
RATE ENVIRONMENT IS PRESENT. FURTHERMORE...MID-LEVEL ASCENT
OVERSPREADING THE AREA...IN ASSOCIATION WITH A VORT MAX ABOUT TO
EMERGE OVER CNTRL/SRN TX PER WATER VAPOR IMAGERY...MAY ALSO LEAD TO
AN UPTICK IN CONVECTION. MLCAPE VALUES OF 1500-2000 J/KG NEAR/SE OF
THE PREFRONTAL TROUGH WILL SUPPORT INTENSE UPDRAFTS WITH SVR HAIL
POSSIBLE...THOUGH ONLY MODEST MID-LEVEL FLOW/DEEP SHEAR COULD LIMIT
THE THREAT. SVR WINDS MAY ALSO BE POSSIBLE...THOUGH THE UNDERCUTTING
NATURE OF THE COLD FRONT MAY MITIGATE THIS CONCERN.

..COHEN/DARROW.. 11/26/2012

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

ATTN...WFO...LCH...HGX...FWD...EWX...

LAT...LON   29779389 29159550 29139676 29699819 30479838 30919740
            31099640 30809520 30679395 29779389

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Nov 26, 3:34 PM CSTMesoscale DiscussionSPCAnderson, Angelina, Camp, Cass, Cherokee, Gregg and 16 more86 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.