Alert archive / Texas / Severe Thunderstorm Watches in 2012

Severe Thunderstorm Watch 184

April 20, 201211 parishes in Louisiana; 49 counties in Texas

The Storm Prediction Center issued this severe thunderstorm watch at Apr 20, 2012, 12:57 PM CDT for 11 parishes in Louisiana; 49 counties in Texas. It was in force for 7 hr.

The area

The outline as issued.

The facts

Issued
Apr 20, 2012, 12:57 PM CDT (17:57 UTC)
Expired
Apr 20, 2012, 8:00 PM CDT
In force
7 hr
Issued by
the Storm Prediction Center
Largest hail expected
2 in
Strongest gust expected
60 kt
All 60 counties

Allen Parish, LA, Beauregard Parish, LA, Calcasieu Parish, LA, Cameron Parish, LA, Grant Parish, LA, Jefferson Davis Parish, LA, Natchitoches Parish, LA, Rapides Parish, LA, Sabine Parish, LA, Vernon Parish, LA, Winn Parish, LA, Aransas County, TX, Austin County, TX, Bastrop County, TX, Bee County, TX, Brazoria County, TX, Brazos County, TX, Burleson County, TX, Caldwell County, TX, Calhoun County, TX, Chambers County, TX, Colorado County, TX, DeWitt County, TX, Fayette County, TX, Fort Bend County, TX, Galveston County, TX, Goliad County, TX, Gonzales County, TX, Grimes County, TX, Guadalupe County, TX, Hardin County, TX, Harris County, TX, Hays County, TX, Houston County, TX, Jackson County, TX, Jasper County, TX, Jefferson County, TX, Karnes County, TX, Lavaca County, TX, Lee County, TX, Liberty County, TX, Madison County, TX, Matagorda County, TX, Montgomery County, TX, Newton County, TX, Orange County, TX, Polk County, TX, Refugio County, TX, Sabine County, TX, San Augustine County, TX, San Jacinto County, TX, Shelby County, TX, Trinity County, TX, Tyler County, TX, Victoria County, TX, Walker County, TX, Waller County, TX, Washington County, TX, Wharton County, TX, Wilson County, TX

The radar

The Houston radar (KHGX), 92 km from the middle of the area, began a volume at 18:00 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.

What SPC expected

The probabilities SPC published with the watch, for the watch area over its life.

Two or more tornadoes
20%
One or more EF2 to EF5 tornadoes
5%
Ten or more severe wind reports
40%
One or more gusts of 65 knots or more
30%
Ten or more severe hail reports
40%
One or more hailstones of 2 inches or more
20%
Six or more combined severe hail and wind reports
80%

Warnings issued inside it

20 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.

IssuedProductOfficeCountiesLasted
Apr 20, 1:38 PM CDTSevere Thunderstorm WarningEWXBastrop, Caldwell, Fayette, Gonzales42 min
Apr 20, 1:43 PM CDTSevere Thunderstorm WarningSHVAngelina, Sabine, San Augustine34 min
Apr 20, 1:49 PM CDTSevere Thunderstorm WarningEWXDeWitt, Gonzales28 min
Apr 20, 2:01 PM CDTSevere Thunderstorm WarningCRPVictoria59 min
Apr 20, 2:03 PM CDTSevere Thunderstorm WarningEWXDeWitt, Lavaca42 min
Apr 20, 3:11 PM CDTSevere Thunderstorm WarningHGXFort Bend, Wharton38 min
Apr 20, 3:14 PM CDTSevere Thunderstorm WarningHGXFort Bend, Harris, Montgomery31 min
Apr 20, 3:18 PM CDTSevere Thunderstorm WarningCRPAransas, Refugio, San Patricio42 min
Apr 20, 3:24 PM CDTSevere Thunderstorm WarningHGXFort Bend, Jackson, Matagorda, Wharton35 min
Apr 20, 3:39 PM CDTSevere Thunderstorm WarningHGXBrazoria, Fort Bend, Harris, Liberty, Montgomery36 min
Apr 20, 3:46 PM CDTSevere Thunderstorm WarningHGXBrazoria, Fort Bend, Matagorda, Wharton29 min
Apr 20, 3:49 PM CDTSevere Thunderstorm WarningCRPBee, Live Oak41 min
Apr 20, 3:50 PM CDTSevere Thunderstorm WarningCRPAransas, Nueces, Refugio, San Patricio55 min
Apr 20, 3:51 PM CDTSevere Thunderstorm WarningHGXBrazoria, Chambers, Fort Bend, Galveston, Harris, Liberty24 min
Apr 20, 3:52 PM CDTSevere Thunderstorm WarningCRPCalhoun, Refugio38 min
Apr 20, 4:10 PM CDTSevere Thunderstorm WarningHGXBrazoria, Galveston65 min
Apr 20, 4:14 PM CDTSevere Thunderstorm WarningHGXBrazoria, Chambers, Galveston, Harris, Liberty28 min
Apr 20, 4:21 PM CDTSevere Thunderstorm WarningCRPCalhoun, Refugio39 min
Apr 20, 4:41 PM CDTSevere Thunderstorm WarningHGXGalveston34 min
Apr 20, 5:31 PM CDTSevere Thunderstorm WarningLCHHardin, Jasper, Jefferson, Newton, Orange, Tyler27 min

Discussions around it

SPC mesoscale discussions over the same counties from four hours before the watch to its end.

The nearest sounding before it

Lake Charles Mun, LA (KLCH), launched 12:00Z, 6.0 hours before the alert went out and 248 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 2012-04-20Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 177 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 2012-04-20The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 2 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
177 J/kg
Mixed-layer CIN
-419 J/kg
Mixed-layer LCL
822 m above ground
0-6 km bulk shear
15 kt
0-1 km storm-relative helicity
2 m²/s²
0-3 km storm-relative helicity
75 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Apr 20, 12:35 PM CDTMesoscale DiscussionSPCBeauregard, Natchitoches, Sabine, Vernon2 hr
Apr 20, 3:44 PM CDTMesoscale DiscussionSPCAllen, Beauregard, Calcasieu, Grant, Jefferson Davis, Natchitoches and 4 more91 min
Apr 20, 6:12 PM CDTMesoscale DiscussionSPCAcadia, Allen, Beauregard, Calcasieu, Cameron, Evangeline and 3 more93 min
Apr 19, 9:13 PM CDTMesoscale DiscussionSPCCooke, Denton, Grayson, Jack, Montague, Wise62 min
Apr 19, 10:49 PM CDTMesoscale DiscussionSPCArcher, Baylor, Clay, Cooke, Foard, Hardeman and 7 more116 min
Apr 20, 1:30 PM CDTMesoscale DiscussionSPCBrooks, Cameron, Duval, Hidalgo, Jim Hogg, Jim Wells and 7 more2 hr
Apr 20, 2:29 PM CDTSevere Thunderstorm WatchSPCBrooks, Cameron, Duval, Hidalgo, Jim Hogg, Jim Wells and 10 more5 hr
Apr 20, 4:48 PM CDTMesoscale DiscussionSPCBrooks, Cameron, Hidalgo, Kenedy, Kleberg, Nueces and 2 more57 min

Nearby

Severe Thunderstorm Watches in Texas, 2012Severe Thunderstorm Watches in Louisiana, 2012Every severe thunderstorm watch 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.