Alert archive / Texas / Mesoscale Discussions in 2012

Mesoscale Discussion 575

April 20, 20129 parishes in Louisiana; 24 counties in Texas

The Storm Prediction Center issued this mesoscale discussion at Apr 20, 2012, 6:12 PM CDT for 9 parishes in Louisiana; 24 counties in Texas. It was in force for 93 min.

The area

The outline as issued.

The facts

Issued
Apr 20, 2012, 6:12 PM CDT (23:12 UTC)
Expired
Apr 20, 2012, 7:45 PM CDT
In force
93 min
Issued by
the Storm Prediction Center
All 33 counties

Acadia Parish, LA, Allen Parish, LA, Beauregard Parish, LA, Calcasieu Parish, LA, Cameron Parish, LA, Evangeline Parish, LA, Jefferson Davis Parish, LA, Rapides Parish, LA, Vernon Parish, LA, Aransas County, TX, Brazoria County, TX, Calhoun County, TX, Chambers County, TX, Fort Bend County, TX, Galveston County, TX, Hardin County, TX, Harris County, TX, Jackson County, TX, Jasper County, TX, Jefferson County, TX, Liberty County, TX, Matagorda County, TX, Montgomery County, TX, Newton County, TX, Orange County, TX, Polk County, TX, Refugio County, TX, San Jacinto County, TX, Tyler County, TX, Victoria County, TX, Walker County, TX, Waller County, TX, Wharton County, TX

The radar

The Houston radar (KHGX), 83 km from the middle of the area, began a volume at 23:12 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, 11.2 hours before the alert went out and 114 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

The text

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

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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, 12:57 PM CDTSevere Thunderstorm WatchSPCAllen, Beauregard, Calcasieu, Cameron, Grant, Jefferson Davis and 5 more7 hr
Apr 20, 3:44 PM CDTMesoscale DiscussionSPCAllen, Beauregard, Calcasieu, Grant, Jefferson Davis, Natchitoches and 4 more91 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

Mesoscale Discussions in Texas, 2012Mesoscale Discussions in Louisiana, 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.