Alert archive / Texas / Severe Thunderstorm Watches in 2011

Severe Thunderstorm Watch 851

September 17, 201116 counties in Oklahoma; 28 counties in Texas

The Storm Prediction Center issued this severe thunderstorm watch at Sep 17, 2011, 3:16 PM CDT for 16 counties in Oklahoma; 28 counties in Texas. It was in force for 8 hr.

The area

The outline as issued.

The facts

Issued
Sep 17, 2011, 3:16 PM CDT (20:16 UTC)
Expired
Sep 17, 2011, 11:00 PM CDT
In force
8 hr
Issued by
the Storm Prediction Center
Largest hail expected
1.7 in
Strongest gust expected
60 kt
All 44 counties

Beckham County, OK, Caddo County, OK, Canadian County, OK, Comanche County, OK, Cotton County, OK, Custer County, OK, Grady County, OK, Greer County, OK, Harmon County, OK, Jackson County, OK, Jefferson County, OK, Kiowa County, OK, Roger Mills County, OK, Stephens County, OK, Tillman County, OK, Washita County, OK, Archer County, TX, Baylor County, TX, Borden County, TX, Childress County, TX, Clay County, TX, Collingsworth County, TX, Cottle County, TX, Dickens County, TX, Fisher County, TX, Foard County, TX, Garza County, TX, Hall County, TX, Hardeman County, TX, Haskell County, TX, Hemphill County, TX, Jones County, TX, Kent County, TX, King County, TX, Knox County, TX, Lipscomb County, TX, Motley County, TX, Scurry County, TX, Shackelford County, TX, Stonewall County, TX, Throckmorton County, TX, Wheeler County, TX, Wichita County, TX, Wilbarger County, TX

The radar

The Altus AFB radar (KFDR), 72 km from the middle of the area, began a volume at 20:19 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
20%
One or more EF2 to EF5 tornadoes
2%
Ten or more severe wind reports
30%
One or more gusts of 65 knots or more
30%
Ten or more severe hail reports
30%
One or more hailstones of 2 inches or more
20%
Six or more combined severe hail and wind reports
70%

Warnings issued inside it

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

IssuedProductOfficeCountiesLasted
Sep 17, 4:18 PM CDTSevere Thunderstorm WarningOUNBeckham, Washita57 min
Sep 17, 4:43 PM CDTSevere Thunderstorm WarningOUNJackson62 min
Sep 17, 4:55 PM CDTSevere Thunderstorm WarningOUNGreer, Harmon11 min
Sep 17, 5:24 PM CDTSevere Thunderstorm WarningOUNTillman66 min
Sep 17, 5:29 PM CDTSevere Thunderstorm WarningOUNKiowa, Washita61 min
Sep 17, 6:01 PM CDTSevere Thunderstorm WarningOUNComanche, Cotton, Kiowa, Tillman59 min
Sep 17, 6:27 PM CDTSevere Thunderstorm WarningOUNCotton, Tillman63 min
Sep 17, 7:00 PM CDTSevere Thunderstorm WarningOUNCotton60 min
Sep 17, 7:15 PM CDTSevere Thunderstorm WarningOUNArcher, Clay, Wichita60 min
Sep 17, 7:30 PM CDTSevere Thunderstorm WarningOUNCotton, Jefferson45 min
Sep 17, 8:34 PM CDTSevere Thunderstorm WarningOUNCotton, Jefferson41 min
Sep 17, 9:16 PM CDTSevere Thunderstorm WarningOUNClay44 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

Amarillo Airport, TX (KAMA), launched 12:00Z, 8.3 hours before the alert went out and 198 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-pSkew-T log-p diagram, Amarillo Airport, TX at 12:00Z on 2011-09-17Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1868 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Amarillo Airport, TX at 12:00Z on 2011-09-17The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 110 square meters per square second.193958Sfc1 km3 km6 km9 kmRMLM
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
1868 J/kg
Mixed-layer CIN
-54 J/kg
Mixed-layer LCL
787 m above ground
0-6 km bulk shear
24 kt
0-1 km storm-relative helicity
110 m²/s²
0-3 km storm-relative helicity
114 m²/s²
Significant tornado parameter
0.0
Supercell composite
2.6

Open this sounding in Storm Lab

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Sep 17, 2:02 PM CDTMesoscale DiscussionSPCAlfalfa, Blaine, Canadian, Custer, Dewey, Ellis and 9 more88 min
Sep 17, 2:30 PM CDTTornado WatchSPCAlfalfa, Blaine, Dewey, Ellis, Garfield, Grant and 11 more9 hr
Sep 17, 2:38 PM CDTMesoscale DiscussionSPCBeckham, Caddo, Comanche, Cotton, Greer, Harmon and 6 more97 min
Sep 17, 5:49 PM CDTMesoscale DiscussionSPCAlfalfa, Blaine, Caddo, Canadian, Comanche, Cotton and 16 more116 min

Nearby

Severe Thunderstorm Watches in Texas, 2011Severe Thunderstorm Watches in Oklahoma, 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; radar from the NEXRAD Level II archive.