Alert archive / Louisiana / Severe Thunderstorm Watches in 2011
Severe Thunderstorm Watch 858
The Storm Prediction Center issued this severe thunderstorm watch at Sep 28, 2011, 5:48 PM CDT for 21 parishes in Louisiana; 11 counties in Texas. It was in force for 6 hr.
The area
The outline as issued.
The facts
- Issued
- Sep 28, 2011, 5:48 PM CDT (22:48 UTC)
- Expired
- Sep 29, 2011, 12:00 AM CDT
- In force
- 6 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 1.5 in
- Strongest gust expected
- 60 kt
All 32 counties
Acadia Parish, LA, Allen Parish, LA, Avoyelles Parish, LA, Beauregard Parish, LA, Calcasieu Parish, LA, Cameron Parish, LA, Evangeline Parish, LA, Grant Parish, LA, Iberia Parish, LA, Jefferson Davis Parish, LA, Lafayette Parish, LA, LaSalle Parish, LA, Natchitoches Parish, LA, Rapides Parish, LA, Sabine Parish, LA, Saint Landry Parish, LA, Saint Martin Parish, LA, St. Mary Parish, LA, Vermilion Parish, LA, Vernon Parish, LA, Winn Parish, LA, Angelina County, TX, Hardin County, TX, Jasper County, TX, Jefferson County, TX, Nacogdoches County, TX, Newton County, TX, Orange County, TX, Sabine County, TX, San Augustine County, TX, Shelby County, TX, Tyler County, TX
What SPC expected
The probabilities SPC published with the watch, for the watch area over its life.
- Two or more tornadoes
- 10%
- One or more EF2 to EF5 tornadoes
- 2%
- Ten or more severe wind reports
- 40%
- One or more gusts of 65 knots or more
- 20%
- Ten or more severe hail reports
- 30%
- One or more hailstones of 2 inches or more
- 10%
- Six or more combined severe hail and wind reports
- 80%
Warnings issued inside it
9 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Sep 28, 5:50 PM CDT | Severe Thunderstorm Warning | SHV | Grant, Natchitoches, Winn | 55 min |
| Sep 28, 6:26 PM CDT | Severe Thunderstorm Warning | LCH | Avoyelles, Rapides | 34 min |
| Sep 28, 6:42 PM CDT | Severe Thunderstorm Warning | LCH | Saint Landry, Saint Martin | 33 min |
| Sep 28, 7:04 PM CDT | Severe Thunderstorm Warning | LCH | Avoyelles, Rapides | 26 min |
| Sep 28, 7:08 PM CDT | Severe Thunderstorm Warning | LCH | Rapides | 52 min |
| Sep 28, 7:57 PM CDT | Severe Thunderstorm Warning | LCH | Rapides | 33 min |
| Sep 28, 8:01 PM CDT | Severe Thunderstorm Warning | LCH | Avoyelles, Saint Landry | 29 min |
| Sep 28, 8:37 PM CDT | Severe Thunderstorm Warning | LCH | Evangeline, Rapides | 23 min |
| Sep 28, 8:49 PM CDT | Severe Thunderstorm Warning | LCH | Avoyelles, Evangeline, Rapides, Saint Landry | 26 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, 10.8 hours before the alert went out and 88 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
- 3608 J/kg
- Mixed-layer CIN
- -10 J/kg
- Mixed-layer LCL
- 709 m above ground
- 0-6 km bulk shear
- 17 kt
- 0-1 km storm-relative helicity
- 63 m²/s²
- 0-3 km storm-relative helicity
- 13 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.9
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Sep 28, 12:10 PM CDT | Mesoscale Discussion | SPC | Acadia, Allen, Ascension, Assumption, Avoyelles, Beauregard and 30 more | 2 hr |
| Sep 28, 1:59 PM CDT | Severe Thunderstorm Watch | SPC | Ascension, Assumption, East Baton Rouge, East Feliciana, Iberville, Jefferson and 16 more | 6 hr |
| Sep 28, 5:19 PM CDT | Mesoscale Discussion | SPC | Acadia, Allen, Ascension, Assumption, Avoyelles, Beauregard and 26 more | 86 min |
Nearby
Severe Thunderstorm Watches in Louisiana, 2011Severe Thunderstorm Watches in Texas, 2011Every severe thunderstorm watch in 2011
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.