Alert archive / Louisiana / Tornado Watches in 2011

Tornado Watch 374

May 25, 20114 states

The Storm Prediction Center issued this tornado watch at May 25, 2011, 3:16 PM CDT for 4 states. It was in force for 7 hr.

The area

The outline as issued.

The facts

Issued: May 25, 2011, 3:16 PM CDT (20:16 UTC)
Expired: May 25, 2011, 9:46 PM CDT
In force: 7 hr
Issued by: the Storm Prediction Center
Largest hail expected: 3 in
Strongest gust expected: 60 kt

All 47 counties

Ashley County, AR, Chicot County, AR, Columbia County, AR, Lafayette County, AR, Miller County, AR, Nevada County, AR, Union County, AR, Bienville Parish, LA, Bossier Parish, LA, Caddo Parish, LA, Caldwell Parish, LA, Claiborne Parish, LA, De Soto Parish, LA, Grant Parish, LA, Jackson Parish, LA, LaSalle Parish, LA, Lincoln Parish, LA, Morehouse Parish, LA, Natchitoches Parish, LA, Ouachita Parish, LA, Red River Parish, LA, Richland Parish, LA, Sabine Parish, LA, Union Parish, LA, Webster Parish, LA, West Carroll Parish, LA, Winn Parish, LA, Bolivar County, MS, Carroll County, MS, Grenada County, MS, Holmes County, MS, Humphreys County, MS, Leflore County, MS, Sunflower County, MS, Washington County, MS, Angelina County, TX, Cass County, TX, Cherokee County, TX, Gregg County, TX, Harrison County, TX, Marion County, TX, Nacogdoches County, TX, Panola County, TX, Rusk County, TX, Sabine County, TX, San Augustine County, TX, Shelby County, TX

The radar

The Shreveport radar (KSHV), 79 km from the middle of the area, began a volume at 20:16 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.

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: 30%
One or more gusts of 65 knots or more: 30%
Ten or more severe hail reports: 70%
One or more hailstones of 2 inches or more: 70%
Six or more combined severe hail and wind reports: 90%

Warnings issued inside it

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

Issued	Product	Office	Counties	Lasted
May 25, 4:13 PM CDT	Severe Thunderstorm Warning	SHV	Harrison, Panola, Rusk	62 min
May 25, 6:26 PM CDT	Severe Thunderstorm Warning	SHV	Sabine	49 min
May 25, 6:37 PM CDT	Severe Thunderstorm Warning	SHV	De Soto, Natchitoches, Red River, Sabine	38 min
May 25, 6:48 PM CDT	Severe Thunderstorm Warning	SHV	Union	42 min
May 25, 7:06 PM CDT	Severe Thunderstorm Warning	JAN	Bolivar	54 min
May 25, 7:14 PM CDT	Severe Thunderstorm Warning	SHV	Natchitoches, Sabine	61 min
May 25, 7:14 PM CDT	Tornado Warning	JAN	Bolivar	61 min
May 25, 7:28 PM CDT	Severe Thunderstorm Warning	JAN	Ashley	25 min
May 25, 7:28 PM CDT	Severe Thunderstorm Warning	SHV	Union	62 min
May 25, 7:38 PM CDT	Tornado Warning	JAN	Bolivar, Sunflower	52 min
May 25, 7:42 PM CDT	Tornado Warning	SHV	Lincoln, Union	48 min
May 25, 8:03 PM CDT	Severe Thunderstorm Warning	SHV	Bienville, Caldwell, Claiborne, Jackson, Lincoln, Ouachita and 2 more	57 min
May 25, 8:14 PM CDT	Severe Thunderstorm Warning	JAN	Chicot	61 min
May 25, 8:18 PM CDT	Severe Thunderstorm Warning	JAN	Ashley	42 min
May 25, 8:29 PM CDT	Tornado Warning	JAN	Bolivar, Sunflower	28 min
May 25, 8:31 PM CDT	Tornado Warning	SHV	Ouachita, Union	30 min
May 25, 8:36 PM CDT	Tornado Warning	JAN	Ashley, Chicot	54 min
May 25, 8:45 PM CDT	Severe Thunderstorm Warning	JAN	Leflore, Sunflower	60 min
May 25, 8:54 PM CDT	Severe Thunderstorm Warning	SHV	Bienville, Caldwell, De Soto, Grant, Jackson, LaSalle and 4 more	66 min
May 25, 8:55 PM CDT	Tornado Warning	JAN	Washington	51 min
May 25, 9:00 PM CDT	Tornado Warning	JAN	Bolivar, Sunflower	32 min
May 25, 9:07 PM CDT	Severe Thunderstorm Warning	JAN	Grenada	53 min
May 25, 9:13 PM CDT	Tornado Warning	SHV	De Soto, Natchitoches, Red River, Sabine	32 min
May 25, 9:27 PM CDT	Flash Flood Warning	JAN	Chicot	60 min
May 25, 9:36 PM CDT	Severe Thunderstorm Warning	JAN	Carroll, Grenada, Leflore, Montgomery, Sunflower	54 min
May 25, 9:42 PM CDT	Severe Thunderstorm Warning	JAN	Morehouse	24 min
May 25, 9:45 PM CDT	Severe Thunderstorm Warning	JAN	Chicot	21 min
May 25, 9:45 PM CDT	Tornado Warning	SHV	Natchitoches, Sabine	30 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 12:00Z, 8.3 hours before the alert went out and 70 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: 1799 J/kg
Mixed-layer CIN: -149 J/kg
Mixed-layer LCL: 925 m above ground
0-6 km bulk shear: 51 kt
0-1 km storm-relative helicity: 383 m²/s²
0-3 km storm-relative helicity: 425 m²/s²
Significant tornado parameter: 1.5
Supercell composite: 19.5

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

252 
WWUS20 KWNS 252019
SEL4
SPC WW 252019
ARZ000-LAZ000-MSZ000-TXZ000-260400-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 374
NWS STORM PREDICTION CENTER NORMAN OK
320 PM CDT WED MAY 25 2011

THE NWS STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF

       SOUTHERN ARKANSAS
       NORTHERN LOUISIANA
       NORTHWEST MISSISSIPPI
       EASTERN TEXAS

EFFECTIVE THIS WEDNESDAY AFTERNOON AND EVENING FROM 320 PM UNTIL
1100 PM CDT.

TORNADOES...HAIL TO 3 INCHES IN DIAMETER...THUNDERSTORM WIND
GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE
AREAS.

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 85 STATUTE
MILES EAST AND WEST OF A LINE FROM 30 MILES NORTH OF MONTICELLO
ARKANSAS TO 5 MILES EAST SOUTHEAST OF LUFKIN TEXAS.  FOR A
COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE
UPDATE (WOUS64 KWNS WOU4).

REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR
TORNADOES AND SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
AND POSSIBLE WARNINGS.

OTHER WATCH INFORMATION...CONTINUE...WW 368...WW 369...WW
370...WW 371...WW 372...WW 373...

DISCUSSION...TSTM DEVELOPMENT IS EXPECTED WITHIN THE NEXT ONE TO TWO
HOURS ALONG COLD FRONT OVER SWRN AR/NERN TX AS WELL AS FARTHER E
WITHIN OPEN WARM SECTOR.  AIR MASS IS EXTREMELY UNSTABLE THIS
AFTERNOON OWING TO A HOT AND VERY MOIST BOUNDARY LAYER WITH MLCAPE
VALUES OF 3000-3500 J/KG.  WHEN COUPLED WITH 40-50 KT OF DEEP WLY
SHEAR...SETUP WILL FAVOR THE DEVELOPMENT OF SUPERCELLS CAPABLE OF
VERY LARGE HAIL.  A FEW TORNADOES WILL ALSO BE POSSIBLE OWING TO AN
ENHANCED BAND OF SWLY WINDS ASSOCIATED WITH THE SRN EXTENSION OF
LLJ.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 3 INCHES. EXTREME TURBULENCE AND SURFACE
WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
600. MEAN STORM MOTION VECTOR 27030.


...MEAD

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 24, 7:42 PM CDT	Mesoscale Discussion	SPC	Benton, Crawford, Little River, Polk, Scott, Sebastian and 2 more	63 min
May 24, 8:05 PM CDT	Tornado Watch	SPC	Baxter, Benton, Boone, Carroll, Clark, Conway and 30 more	7 hr
May 24, 11:24 PM CDT	Mesoscale Discussion	SPC	Baxter, Boone, Carroll, Clark, Conway, Franklin and 21 more	96 min
May 25, 12:48 AM CDT	Mesoscale Discussion	SPC	Clay, Craighead, Fulton, Greene, Independence, Jackson and 4 more	57 min
May 25, 7:31 AM CDT	Mesoscale Discussion	SPC	Clay, Craighead, Crittenden, Cross, Greene, Mississippi and 1 more	59 min
May 25, 9:54 AM CDT	Mesoscale Discussion	SPC	Baxter, Boone, Carroll, Clay, Cleburne, Conway and 33 more	96 min
May 25, 10:18 AM CDT	Mesoscale Discussion	SPC	Fulton, Independence, Izard, Jackson, St. Francis, Sharp and 2 more	57 min
May 25, 10:37 AM CDT	Tornado Watch	SPC	Baxter, Boone, Carroll, Fulton, Izard, Madison and 5 more	7 hr
May 25, 11:02 AM CDT	Mesoscale Discussion	SPC	Clay	28 min
May 25, 11:52 AM CDT	Mesoscale Discussion	SPC	Arkansas, Clark, Clay, Cleburne, Cleveland, Conway and 38 more	83 min
May 25, 12:28 PM CDT	Tornado Watch PDS	SPC	Arkansas, Baxter, Bradley, Calhoun, Clark, Clay and 41 more	8 hr
May 25, 1:53 PM CDT	Mesoscale Discussion	SPC	Bradley, Calhoun, Clark, Columbia, Dallas, Hempstead and 9 more	2 hr
May 25, 2:56 PM CDT	Mesoscale Discussion	SPC	Arkansas, Calhoun, Clark, Clay, Cleburne, Cleveland and 33 more	94 min
May 25, 3:10 PM CDT	Mesoscale Discussion	SPC	Clay	95 min
May 25, 5:56 PM CDT	Mesoscale Discussion	SPC	Arkansas, Craighead, Crittenden, Cross, Greene, Lee and 5 more	64 min
May 24, 11:00 PM CDT	Mesoscale Discussion	SPC	Anderson, Bell, Burnet, Coryell, Falls, Freestone and 6 more	60 min
May 24, 11:22 PM CDT	Severe Thunderstorm Watch	SPC	Anderson, Bell, Coryell, Falls, Freestone, Henderson and 7 more	5 hr
May 25, 3:10 AM CDT	Mesoscale Discussion	SPC	Bastrop, Bell, Blanco, Brazos, Burleson, Burnet and 8 more	95 min
May 25, 5:15 PM CDT	Mesoscale Discussion	SPC	Anderson, Austin, Bastrop, Brazos, Burleson, Caldwell and 23 more	60 min

Nearby

Tornado Watches in Louisiana, 2011 Tornado Watches in Texas, 2011 Tornado Watches in Mississippi, 2011 Every tornado 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; radar from the NEXRAD Level II archive.