Alert archive / Louisiana / Tornado Watches in 2009
Tornado Watch 773
The Storm Prediction Center issued this tornado watch at Oct 22, 2009, 4:35 PM CDT for 11 parishes in Louisiana; 6 counties in Mississippi. It was in force for 4 hr.
The area
The outline as issued.
The facts
- Issued
- Oct 22, 2009, 4:35 PM CDT (21:35 UTC)
- Expired
- Oct 22, 2009, 8:54 PM CDT
- In force
- 4 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 1 in
- Strongest gust expected
- 60 kt
Counties Jefferson Parish, LA, Lafourche Parish, LA, Orleans Parish, LA, Plaquemines Parish, LA, Saint Bernard Parish, LA, Saint Charles Parish, LA, Saint John the Baptist Parish, LA, Saint Tammany Parish, LA, Tangipahoa Parish, LA, Terrebonne Parish, LA, Washington Parish, LA, Hancock County, MS, Harrison County, MS, Jackson County, MS, Pearl River County, MS, Pike County, MS, Walthall County, MS
What SPC expected
The probabilities SPC published with the watch, for the watch area over its life.
- Two or more tornadoes
- 30%
- One or more EF2 to EF5 tornadoes
- 20%
- Ten or more severe wind reports
- 20%
- One or more gusts of 65 knots or more
- 10%
- Ten or more severe hail reports
- 5%
- One or more hailstones of 2 inches or more
- 5%
- Six or more combined severe hail and wind reports
- 40%
Warnings issued inside it
2 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Oct 22, 5:08 PM CDT | Severe Thunderstorm Warning | LIX | Lafourche, Terrebonne | 52 min |
| Oct 22, 6:40 PM CDT | Tornado Warning | LIX | Terrebonne | 35 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
Slidell Radar S, LA (KSIL), launched 12:00Z, 9.6 hours before the alert went out and 30 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
- 6 J/kg
- Mixed-layer CIN
- -39 J/kg
- Mixed-layer LCL
- 917 m above ground
- 0-6 km bulk shear
- 19 kt
- 0-1 km storm-relative helicity
- 123 m²/s²
- 0-3 km storm-relative helicity
- 263 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Oct 22, 5:35 AM CDT | Mesoscale Discussion | SPC | Beauregard, Calcasieu, De Soto, Sabine, Vernon | 85 min |
| Oct 22, 5:55 AM CDT | Tornado Watch | SPC | Acadia, Allen, Beauregard, Calcasieu, Caldwell, Cameron and 12 more | 6 hr |
| Oct 22, 7:48 AM CDT | Mesoscale Discussion | SPC | Acadia, Allen, Avoyelles, Beauregard, Bienville, Calcasieu and 19 more | 117 min |
| Oct 22, 10:14 AM CDT | Mesoscale Discussion | SPC | Acadia, Allen, Beauregard, Calcasieu, Cameron, Evangeline and 10 more | 91 min |
| Oct 22, 11:27 AM CDT | Mesoscale Discussion | SPC | Ascension, Assumption, Avoyelles, Caldwell, Catahoula, Concordia and 26 more | 93 min |
| Oct 22, 11:58 AM CDT | Tornado Watch | SPC | Acadia, Allen, Ascension, Assumption, Avoyelles, Beauregard and 40 more | 7 hr |
| Oct 22, 3:36 PM CDT | Mesoscale Discussion | SPC | Ascension, Assumption, Catahoula, Concordia, East Baton Rouge, East Carroll and 14 more | 114 min |
| Oct 22, 6:26 PM CDT | Mesoscale Discussion | SPC | Ascension, Assumption, East Baton Rouge, East Carroll, East Feliciana, Livingston and 5 more | 34 min |
| Oct 22, 6:55 PM CDT | Tornado Watch | SPC | Attala, Bolivar, Carroll, Copiah, Covington, Forrest and 22 more | 3 hr |
Nearby
Tornado Watches in Louisiana, 2009Tornado Watches in Mississippi, 2009Every tornado watch 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.