Alert archive / Texas / Mesoscale Discussions in 2009
Mesoscale Discussion 794
The Storm Prediction Center issued this mesoscale discussion at May 11, 2009, 1:05 PM CDT for 17 parishes in Louisiana; 22 counties in Texas. It was in force for 85 min.
The area
The outline as issued.
The facts
- Issued
- May 11, 2009, 1:05 PM CDT (18:05 UTC)
- Expired
- May 11, 2009, 2:30 PM CDT
- In force
- 85 min
- Issued by
- the Storm Prediction Center
All 39 counties
Acadia Parish, LA, Allen Parish, LA, Avoyelles Parish, LA, Beauregard Parish, LA, Calcasieu Parish, LA, Cameron Parish, LA, Catahoula Parish, LA, Evangeline Parish, LA, Grant Parish, LA, Jefferson Davis Parish, LA, LaSalle Parish, LA, Natchitoches Parish, LA, Rapides Parish, LA, Sabine Parish, LA, Saint Landry Parish, LA, Vernon Parish, LA, Winn Parish, LA, Angelina County, TX, Chambers County, TX, Grimes County, TX, Hardin County, TX, Harris County, TX, Houston County, TX, Jasper County, TX, Jefferson County, TX, Liberty County, TX, Madison County, TX, Montgomery County, TX, Nacogdoches County, TX, Newton County, TX, Orange County, TX, Polk County, TX, Sabine County, TX, San Augustine County, TX, San Jacinto County, TX, Shelby County, TX, Trinity County, TX, Tyler County, TX, Walker County, TX
The watches that followed
Watches SPC issued over any of the same counties within four hours of this discussion.
The nearest sounding before it
Shreveport, LA (KSHV), launched 12:00Z, 6.1 hours before the alert went out and 189 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.
- Mixed-layer CAPE
- 129 J/kg
- Mixed-layer CIN
- -187 J/kg
- Mixed-layer LCL
- 458 m above ground
- 0-6 km bulk shear
- 35 kt
- 0-1 km storm-relative helicity
- 147 m²/s²
- 0-3 km storm-relative helicity
- 137 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 2.2
The text
As transmitted, in the capitals the NWS used until 2016.
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</html>SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 10, 7:29 PM CDT | Mesoscale Discussion | SPC | Concordia, Grant | 61 min |
| May 10, 7:50 PM CDT | Severe Thunderstorm Watch | SPC | Catahoula, Concordia, Tensas | 5 hr |
| May 11, 2:20 PM CDT | Mesoscale Discussion | SPC | Allen, Avoyelles, Catahoula, Concordia, East Baton Rouge, East Feliciana and 13 more | 55 min |
| May 11, 2:52 PM CDT | Severe Thunderstorm Watch | SPC | Acadia, Allen, Avoyelles, Beauregard, Calcasieu, Cameron and 21 more | 5 hr |
| May 11, 6:15 PM CDT | Mesoscale Discussion | SPC | Ascension, Assumption, Iberville, Livingston, Saint Charles, Saint James and 2 more | 90 min |
Nearby
Mesoscale Discussions in Texas, 2009Mesoscale Discussions in Louisiana, 2009Every 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.