Alert archive / Louisiana / Mesoscale Discussions in 2009

Mesoscale Discussion 452

April 12, 200917 parishes in Louisiana; 14 counties in Texas

The Storm Prediction Center issued this mesoscale discussion at Apr 12, 2009, 7:39 AM CDT for 17 parishes in Louisiana; 14 counties in Texas. It was in force for 66 min.

The area

The outline as issued.

The facts

Issued: Apr 12, 2009, 7:39 AM CDT (12:39 UTC)
Expired: Apr 12, 2009, 8:45 AM CDT
In force: 66 min
Issued by: the Storm Prediction Center

All 31 counties

Acadia Parish, LA, Allen Parish, LA, Beauregard Parish, LA, Calcasieu Parish, LA, Cameron Parish, LA, Evangeline Parish, LA, Iberia Parish, LA, Iberville Parish, LA, Jefferson Davis Parish, LA, Lafayette Parish, LA, Pointe Coupee Parish, LA, Rapides Parish, LA, Saint Landry Parish, LA, Saint Martin Parish, LA, St. Mary Parish, LA, Vermilion Parish, LA, Vernon Parish, LA, Brazoria County, TX, Chambers County, TX, Galveston County, TX, Hardin County, TX, Harris County, TX, Jasper County, TX, Jefferson County, TX, Liberty County, TX, Montgomery County, TX, Newton County, TX, Orange County, TX, Polk County, TX, San Jacinto County, TX, Tyler County, TX

The radar

The Lake Charles radar (KLCH), 37 km from the middle of the area, began a volume at 12:38 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 watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

Tornado Watch 143Apr 12, 8:00 AM CDT

The nearest sounding before it

Lake Charles Mun, LA (KLCH), launched 12:00Z, 0.7 hours before the alert went out and 38 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-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

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: 880 J/kg
Mixed-layer CIN: -259 J/kg
Mixed-layer LCL: 506 m above ground
0-6 km bulk shear: 49 kt
0-1 km storm-relative helicity: 326 m²/s²
0-3 km storm-relative helicity: 463 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 5.3

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.

Issued	Product	Office	Counties	Lasted
Apr 12, 7:13 AM CDT	Mesoscale Discussion	SPC	East Carroll, Morehouse, Union, West Carroll	92 min
Apr 12, 7:58 AM CDT	Tornado Watch	SPC	Acadia, Allen, Avoyelles, Beauregard, Calcasieu, Cameron and 10 more	8 hr
Apr 12, 9:19 AM CDT	Mesoscale Discussion	SPC	Bienville, Bossier, Caddo, Caldwell, De Soto, Jackson and 10 more	56 min
Apr 12, 9:30 AM CDT	Severe Thunderstorm Watch	SPC	Bienville, Bossier, Caddo, Caldwell, Claiborne, De Soto and 11 more	7 hr
Apr 12, 10:53 AM CDT	Mesoscale Discussion	SPC	Acadia, Allen, Beauregard, Calcasieu, Cameron, Evangeline and 2 more	2 hr
Apr 12, 12:00 PM CDT	Mesoscale Discussion	SPC	Bienville, Caldwell, Claiborne, Jackson, Lincoln, Morehouse and 8 more	90 min
Apr 12, 1:02 PM CDT	Mesoscale Discussion	SPC	Ascension, Assumption, Concordia, East Baton Rouge, East Feliciana, Franklin and 14 more	88 min
Apr 12, 1:53 PM CDT	Tornado Watch	SPC	Ascension, Assumption, Catahoula, Concordia, East Baton Rouge, East Carroll and 26 more	7 hr
Apr 12, 5:49 PM CDT	Mesoscale Discussion	SPC	Catahoula, Concordia, East Carroll, Franklin, Madison, Richland and 2 more	86 min
Apr 11, 7:41 PM CDT	Severe Thunderstorm Watch	SPC	Callahan, Coke, Coleman, Concho, Crockett, Fisher and 14 more	5 hr
Apr 11, 9:09 PM CDT	Mesoscale Discussion	SPC	Archer, Baylor, Brown, Callahan, Clay, Coke and 30 more	96 min
Apr 11, 11:44 PM CDT	Mesoscale Discussion	SPC	Brown, Callahan, Clay, Coleman, Comanche, Concho and 22 more	91 min
Apr 12, 12:39 AM CDT	Severe Thunderstorm Watch	SPC	Bandera, Brown, Callahan, Coke, Coleman, Comanche and 38 more	4 hr
Apr 12, 3:55 AM CDT	Mesoscale Discussion	SPC	Atascosa, Austin, Bandera, Bastrop, Bell, Bexar and 49 more	95 min
Apr 12, 4:37 AM CDT	Mesoscale Discussion	SPC	Brazoria, Chambers, Fort Bend, Hardin, Harris, Jasper and 8 more	83 min
Apr 12, 2:24 PM CDT	Mesoscale Discussion	SPC	Archer, Baylor, Clay, Foard, Hardeman, Jack and 7 more	96 min
Apr 12, 5:20 PM CDT	Mesoscale Discussion	SPC	Clay, Collin, Cooke, Denton, Grayson, Jack and 5 more	55 min

Nearby

Mesoscale Discussions in Louisiana, 2009 Mesoscale Discussions in Texas, 2009 Every mesoscale discussion in 2009

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.