Alert archive / Texas / Mesoscale Discussions in 2012

Mesoscale Discussion 1452

July 12, 20129 counties in Texas

The Storm Prediction Center issued this mesoscale discussion at Jul 12, 2012, 4:21 AM CDT for 9 counties in Texas. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued
Jul 12, 2012, 4:21 AM CDT (09:21 UTC)
Expired
Jul 12, 2012, 6:45 AM CDT
In force
2 hr
Issued by
the Storm Prediction Center

Counties Angelina County, TX, Austin County, TX, Colorado County, TX, Montgomery County, TX, Polk County, TX, San Augustine County, TX, San Jacinto County, TX, Tyler County, TX, Waller County, TX

The radar

The Houston radar (KHGX), 106 km from the middle of the area, began a volume at 09:21 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 00:00Z, 9.4 hours before the alert went out and 211 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 00:00Z on 2012-07-12Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1221 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 00:00Z on 2012-07-12The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -35 square meters per square second.1939Sfc1 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
1221 J/kg
Mixed-layer CIN
-2 J/kg
Mixed-layer LCL
706 m above ground
0-6 km bulk shear
7 kt
0-1 km storm-relative helicity
-35 m²/s²
0-3 km storm-relative helicity
-25 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.

714 
ACUS11 KWNS 120921
SWOMCD
SPC MCD 120921 
TXZ000-121145-

MESOSCALE DISCUSSION 1452
NWS STORM PREDICTION CENTER NORMAN OK
0421 AM CDT THU JUL 12 2012

AREAS AFFECTED...SERN TX

CONCERNING...HEAVY RAINFALL 

VALID 120921Z - 121145Z

SUMMARY...A SW/NE-ORIENTED BAND OF HEAVY RAIN SHOULD PERSIST NEXT
FEW HOURS WITH RAINFALL ACCUMULATIONS EXCEEDING 2 IN/HR.

DISCUSSION...A 10-15 MILE WIDE CONVECTIVE BAND HAS BLOSSOMED DURING
THE PAST HOUR...CENTERED FROM COLORADO TO POLK COUNTIES AS OF 0910Z.
THIS ACTIVITY APPEARS TO HAVE FORMED IN RESPONSE TO MODERATE
LOW-LEVEL WAA /INFERRED BY HGX VWP DATA/ AND PERHAPS AIDED BY A
REMNANT MCV JUST E OF GALVESTON BAY. WITHIN THIS BAND...THE CONROE
ASOS /KCXO/ MEASURED 2.78 INCHES OF RAIN IN THE 72 MINUTES ENDING AT
0913Z. WITH GPS PW VALUES AROUND 2.25 INCHES...RAINFALL
ACCUMULATIONS COULD BECOME SUBSTANTIAL OWING TO MODEST MEAN SWLY
FLOW PARALLEL TO THE INITIATION CORRIDOR...RESULTING IN REPEATED
TRAINING OF CELLS. THIS REGIME SHOULD PERSIST FOR AT LEAST A FEW
HOURS UNTIL LAPSE RATES BECOME SUFFICIENTLY NEUTRAL AND CONVECTION
WANES.

..GRAMS.. 07/12/2012

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

ATTN...WFO...LCH...SHV...HGX...EWX...

LAT...LON   29779684 30619534 31299459 31409415 31249375 31069381
            30219478 29819568 29549649 29609681 29779684

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.