Alert archive / Louisiana / Tornado Watches in 2009

Tornado Watch 807

December 24, 2009Ashley County, Chicot County, Union County, Arkansas; 53 parishes in Louisiana; 8 counties in Mississippi

The Storm Prediction Center issued this tornado watch at Dec 24, 2009, 4:50 AM CST for Ashley County, Chicot County, Union County, Arkansas; 53 parishes in Louisiana; 8 counties in Mississippi. It was in force for 7 hr.

The area

The outline as issued.

The facts

Issued: Dec 24, 2009, 4:50 AM CST (10:50 UTC)
Expired: Dec 24, 2009, 12:19 PM CST
In force: 7 hr
Issued by: the Storm Prediction Center
Largest hail expected: 1 in
Strongest gust expected: 65 kt

All 64 counties

Ashley County, AR, Chicot County, AR, Union County, AR, Acadia Parish, LA, Allen Parish, LA, Ascension Parish, LA, Assumption Parish, LA, Avoyelles Parish, LA, Beauregard Parish, LA, Bienville Parish, LA, Calcasieu Parish, LA, Caldwell Parish, LA, Cameron Parish, LA, Catahoula Parish, LA, Claiborne Parish, LA, Concordia Parish, LA, De Soto Parish, LA, East Baton Rouge Parish, LA, East Carroll Parish, LA, East Feliciana Parish, LA, Evangeline Parish, LA, Franklin Parish, LA, Grant Parish, LA, Iberia Parish, LA, Iberville Parish, LA, Jackson Parish, LA, Jefferson Davis Parish, LA, Lafayette Parish, LA, Lafourche Parish, LA, LaSalle Parish, LA, Lincoln Parish, LA, Livingston Parish, LA, Madison Parish, LA, Morehouse Parish, LA, Natchitoches Parish, LA, Ouachita Parish, LA, Pointe Coupee Parish, LA, Rapides Parish, LA, Red River Parish, LA, Richland Parish, LA, Sabine Parish, LA, Saint Helena Parish, LA, Saint James Parish, LA, Saint John the Baptist Parish, LA, Saint Landry Parish, LA, Saint Martin Parish, LA, St. Mary Parish, LA, Tensas Parish, LA, Terrebonne Parish, LA, Union Parish, LA, Vermilion Parish, LA, Vernon Parish, LA, West Baton Rouge Parish, LA, West Carroll Parish, LA, West Feliciana Parish, LA, Winn Parish, LA, Adams County, MS, Amite County, MS, Claiborne County, MS, Franklin County, MS, Issaquena County, MS, Jefferson County, MS, Warren County, MS, Wilkinson County, MS

What SPC expected

The probabilities SPC published with the watch, for the watch area over its life.

Two or more tornadoes: 50%
One or more EF2 to EF5 tornadoes: 30%
Ten or more severe wind reports: 40%
One or more gusts of 65 knots or more: 30%
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: 70%

Warnings issued inside it

55 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.

Issued	Product	Office	Counties	Lasted
Dec 24, 4:54 AM CST	Severe Thunderstorm Warning	SHV	Bienville, Claiborne, Lincoln, Union	51 min
Dec 24, 4:59 AM CST	Severe Thunderstorm Warning	SHV	De Soto, Sabine	46 min
Dec 24, 5:21 AM CST	Severe Thunderstorm Warning	SHV	Bienville, Natchitoches, Red River	39 min
Dec 24, 5:24 AM CST	Tornado Warning	SHV	Bienville, Natchitoches, Red River	51 min
Dec 24, 5:27 AM CST	Tornado Warning	SHV	Caldwell, LaSalle	63 min
Dec 24, 5:32 AM CST	Flash Flood Warning	SHV	Columbia, Union	4 hr
Dec 24, 5:40 AM CST	Tornado Warning	SHV	Bienville, Lincoln	50 min
Dec 24, 5:54 AM CST	Flash Flood Warning	SHV	Bienville, De Soto, Natchitoches, Red River, Sabine	4 hr
Dec 24, 6:14 AM CST	Severe Thunderstorm Warning	SHV	Bienville, Claiborne, Lincoln	46 min
Dec 24, 6:18 AM CST	Tornado Warning	SHV	Natchitoches	42 min
Dec 24, 6:49 AM CST	Severe Thunderstorm Warning	SHV	Union	56 min
Dec 24, 6:53 AM CST	Tornado Warning	SHV	Bienville, Natchitoches, Red River	52 min
Dec 24, 7:18 AM CST	Tornado Warning	SHV	Bienville, Claiborne, Lincoln, Union	42 min
Dec 24, 7:20 AM CST	Tornado Warning	LCH	Avoyelles, Evangeline, Saint Landry	25 min
Dec 24, 7:30 AM CST	Severe Thunderstorm Warning	SHV	Bienville, Jackson, Lincoln	45 min
Dec 24, 7:33 AM CST	Severe Thunderstorm Warning	SHV	Union	42 min
Dec 24, 7:34 AM CST	Severe Thunderstorm Warning	JAN	Catahoula, Concordia, Franklin	33 min
Dec 24, 7:37 AM CST	Tornado Warning	LCH	Acadia, Saint Landry	23 min
Dec 24, 7:42 AM CST	Tornado Warning	LCH	Avoyelles	33 min
Dec 24, 7:45 AM CST	Tornado Warning	LCH	Acadia, Evangeline, Saint Landry	30 min
Dec 24, 7:51 AM CST	Tornado Warning	SHV	Bienville, Claiborne, Jackson, Lincoln, Union	54 min
Dec 24, 8:02 AM CST	Flash Flood Warning	JAN	Ashley, Chicot	4 hr
Dec 24, 8:09 AM CST	Tornado Warning	JAN	Catahoula, Concordia	38 min
Dec 24, 8:22 AM CST	Tornado Warning	LCH	Evangeline	23 min
Dec 24, 8:32 AM CST	Tornado Warning	LCH	Iberia, Vermilion	28 min
Dec 24, 8:34 AM CST	Tornado Warning	LCH	Avoyelles, Evangeline, Rapides	26 min
Dec 24, 8:39 AM CST	Tornado Warning	LCH	Saint Landry	36 min
Dec 24, 8:52 AM CST	Severe Thunderstorm Warning	JAN	Ashley	53 min
Dec 24, 8:56 AM CST	Tornado Warning	LCH	Iberia, Lafayette, Saint Martin	34 min
Dec 24, 9:02 AM CST	Flash Flood Warning	JAN	East Carroll, Franklin, Madison, Tensas	3 hr
Dec 24, 9:03 AM CST	Tornado Warning	LCH	Iberia, St. Mary	27 min
Dec 24, 9:10 AM CST	Tornado Warning	JAN	Ashley	54 min
Dec 24, 9:17 AM CST	Tornado Warning	LCH	Saint Landry, Saint Martin	28 min
Dec 24, 9:19 AM CST	Severe Thunderstorm Warning	JAN	Catahoula, Concordia	56 min
Dec 24, 9:23 AM CST	Severe Thunderstorm Warning	SHV	Caldwell, Ouachita	37 min
Dec 24, 9:25 AM CST	Severe Thunderstorm Warning	JAN	Franklin, Morehouse, Richland	65 min
Dec 24, 9:27 AM CST	Tornado Warning	LCH	Iberia, Saint Martin	33 min
Dec 24, 9:35 AM CST	Tornado Warning	JAN	Catahoula, Concordia, Franklin, Tensas	41 min
Dec 24, 9:38 AM CST	Severe Thunderstorm Warning	JAN	Ashley, Chicot	24 min
Dec 24, 9:39 AM CST	Flash Flood Warning	JAN	Bolivar, Issaquena, Sharkey, Warren, Washington	3 hr
Dec 24, 9:41 AM CST	Severe Thunderstorm Warning	LIX	Pointe Coupee	64 min
Dec 24, 9:45 AM CST	Severe Thunderstorm Warning	JAN	Concordia, Tensas	60 min
Dec 24, 9:45 AM CST	Tornado Warning	LIX	Iberville, Pointe Coupee	45 min
Dec 24, 9:54 AM CST	Severe Thunderstorm Warning	LIX	Iberville, West Baton Rouge	36 min
Dec 24, 9:56 AM CST	Severe Thunderstorm Warning	JAN	Ashley	27 min
Dec 24, 10:01 AM CST	Tornado Warning	LIX	Iberville, Pointe Coupee, West Baton Rouge	29 min
Dec 24, 10:08 AM CST	Severe Thunderstorm Warning	JAN	Franklin, Morehouse, Richland, West Carroll	67 min
Dec 24, 10:17 AM CST	Severe Thunderstorm Warning	JAN	Franklin, Madison, Richland, Tensas	58 min
Dec 24, 10:32 AM CST	Severe Thunderstorm Warning	JAN	East Carroll, Madison, West Carroll	58 min
Dec 24, 10:40 AM CST	Severe Thunderstorm Warning	JAN	Adams, Claiborne, Franklin, Jefferson	65 min
Dec 24, 10:45 AM CST	Severe Thunderstorm Warning	LIX	Ascension, Assumption, Lafourche, Livingston, Saint James	45 min
Dec 24, 10:45 AM CST	Tornado Warning	LIX	Ascension, East Baton Rouge, Iberville, Livingston	30 min
Dec 24, 11:11 AM CST	Tornado Warning	LIX	Livingston, Saint Helena	34 min
Dec 24, 11:19 AM CST	Tornado Warning	LIX	Ascension, Livingston, Tangipahoa	26 min
Dec 24, 11:25 AM CST	Severe Thunderstorm Warning	LIX	Assumption, Lafourche, Saint Charles, Saint James, Saint John the Baptist, Terrebonne	65 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

Shreveport, LA (KSHV), launched 00:00Z, 10.8 hours before the alert went out and 173 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: 649 J/kg
Mixed-layer CIN: -5 J/kg
Mixed-layer LCL: 446 m above ground
0-6 km bulk shear: 42 kt
0-1 km storm-relative helicity: 329 m²/s²
0-3 km storm-relative helicity: 329 m²/s²
Significant tornado parameter: 1.0
Supercell composite: 5.8

Open this sounding in Storm Lab

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Dec 23, 7:50 PM CST	Mesoscale Discussion	SPC	Clark, Columbia, Hempstead, Howard, Lafayette, Little River and 7 more	85 min
Dec 23, 8:48 PM CST	Tornado Watch	SPC	Columbia, Hempstead, Howard, Lafayette, Little River, Miller and 1 more	9 hr
Dec 23, 11:06 PM CST	Mesoscale Discussion	SPC	Clark, Columbia, Dallas, Hempstead, Hot Spring, Howard and 7 more	114 min
Dec 24, 3:30 AM CST	Mesoscale Discussion	SPC	Ashley, Bradley, Calhoun, Chicot, Columbia, Lafayette and 2 more	2 hr
Dec 24, 7:30 AM CST	Mesoscale Discussion	SPC	Ashley	90 min
Dec 24, 10:13 AM CST	Mesoscale Discussion	SPC	Ashley, Chicot, Union	62 min
Dec 24, 9:34 AM CST	Mesoscale Discussion	SPC	Ascension, Assumption, East Baton Rouge, East Feliciana, Iberville, Jefferson and 16 more	56 min
Dec 24, 10:37 AM CST	Tornado Watch	SPC	Jefferson, Orleans, Plaquemines, Saint Bernard, Saint Charles, Saint Tammany and 2 more	7 hr
Dec 24, 1:14 PM CST	Mesoscale Discussion	SPC	Jefferson, Orleans, Plaquemines, Saint Bernard, Saint Tammany, Washington	61 min
Dec 24, 3:33 PM CST	Mesoscale Discussion	SPC	Clarke, Forrest, George, Greene, Harrison, Jackson and 11 more	57 min

Nearby

Tornado Watches in Louisiana, 2009 Tornado Watches in Mississippi, 2009 Tornado Watches in Arkansas, 2009 Every 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.