Alert archive / Texas / Severe Thunderstorm Watches in 2011

Severe Thunderstorm Watch 316

May 21, 201135 counties in Texas

The Storm Prediction Center issued this severe thunderstorm watch at May 21, 2011, 1:45 PM CDT for 35 counties in Texas. It was in force for 7 hr.

The area

The outline as issued.

The facts

Issued: May 21, 2011, 1:45 PM CDT (18:45 UTC)
Expired: May 21, 2011, 9:00 PM CDT
In force: 7 hr
Issued by: the Storm Prediction Center
Largest hail expected: 2.5 in
Strongest gust expected: 60 kt

All 35 counties

Bandera County, TX, Bell County, TX, Blanco County, TX, Bosque County, TX, Burnet County, TX, Comal County, TX, Comanche County, TX, Coryell County, TX, Dallas County, TX, Ellis County, TX, Erath County, TX, Falls County, TX, Gillespie County, TX, Hamilton County, TX, Hays County, TX, Hill County, TX, Hood County, TX, Johnson County, TX, Kendall County, TX, Kerr County, TX, Kimble County, TX, Lampasas County, TX, Limestone County, TX, Llano County, TX, Mason County, TX, McLennan County, TX, Mills County, TX, Navarro County, TX, Parker County, TX, Real County, TX, San Saba County, TX, Somervell County, TX, Tarrant County, TX, Travis County, TX, Williamson County, TX

The radar

The Ft Hood radar (KGRK), 111 km from the middle of the area, began a volume at 18:42 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: 5%
Ten or more severe wind reports: 30%
One or more gusts of 65 knots or more: 30%
Ten or more severe hail reports: 40%
One or more hailstones of 2 inches or more: 70%
Six or more combined severe hail and wind reports: 80%

Warnings issued inside it

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

Issued	Product	Office	Counties	Lasted
May 21, 2:51 PM CDT	Severe Thunderstorm Warning	FWD	Hamilton	54 min
May 21, 3:13 PM CDT	Severe Thunderstorm Warning	FWD	Erath	47 min
May 21, 3:37 PM CDT	Severe Thunderstorm Warning	FWD	Mills	38 min
May 21, 3:39 PM CDT	Severe Thunderstorm Warning	FWD	Hood, Somervell	66 min
May 21, 3:41 PM CDT	Severe Thunderstorm Warning	FWD	Coryell, Hamilton	64 min
May 21, 3:48 PM CDT	Severe Thunderstorm Warning	SJT	San Saba	27 min
May 21, 3:52 PM CDT	Tornado Warning	FWD	Coryell, Hamilton, Lampasas	38 min
May 21, 4:08 PM CDT	Severe Thunderstorm Warning	FWD	Lampasas	67 min
May 21, 4:12 PM CDT	Severe Thunderstorm Warning	FWD	Mills	21 min
May 21, 4:27 PM CDT	Tornado Warning	FWD	Coryell, Hamilton	63 min
May 21, 4:44 PM CDT	Severe Thunderstorm Warning	FWD	Coryell	61 min
May 21, 4:58 PM CDT	Severe Thunderstorm Warning	EWX	Burnet, Llano, Williamson	47 min
May 21, 5:10 PM CDT	Severe Thunderstorm Warning	FWD	Lampasas	65 min
May 21, 5:34 PM CDT	Severe Thunderstorm Warning	FWD	Hamilton	56 min
May 21, 5:37 PM CDT	Severe Thunderstorm Warning	FWD	Coryell	53 min
May 21, 5:44 PM CDT	Severe Thunderstorm Warning	EWX	Burnet, Williamson	46 min
May 21, 6:00 PM CDT	Severe Thunderstorm Warning	EWX	Burnet, Llano	45 min
May 21, 6:26 PM CDT	Severe Thunderstorm Warning	FWD	Coryell	64 min
May 21, 6:29 PM CDT	Severe Thunderstorm Warning	EWX	Burnet, Williamson	46 min
May 21, 6:52 PM CDT	Severe Thunderstorm Warning	EWX	Burnet, Williamson	38 min
May 21, 6:59 PM CDT	Tornado Warning	EWX	Burnet	31 min
May 21, 6:59 PM CDT	Severe Thunderstorm Warning	FWD	Lampasas	47 min
May 21, 7:10 PM CDT	Severe Thunderstorm Warning	EWX	Burnet, Travis, Williamson	50 min
May 21, 7:12 PM CDT	Severe Thunderstorm Warning	SJT	San Saba	48 min
May 21, 7:27 PM CDT	Tornado Warning	EWX	Burnet, Williamson	33 min
May 21, 7:33 PM CDT	Severe Thunderstorm Warning	FWD	Coryell	42 min
May 21, 7:44 PM CDT	Severe Thunderstorm Warning	EWX	Burnet, Williamson	46 min
May 21, 7:50 PM CDT	Severe Thunderstorm Warning	EWX	Burnet, Llano	40 min
May 21, 7:59 PM CDT	Tornado Warning	EWX	Burnet, Williamson	31 min
May 21, 8:11 PM CDT	Tornado Warning	EWX	Burnet, Llano	34 min
May 21, 8:27 PM CDT	Severe Thunderstorm Warning	EWX	Williamson	48 min
May 21, 8:27 PM CDT	Tornado Warning	EWX	Williamson	33 min
May 21, 8:32 PM CDT	Severe Thunderstorm Warning	EWX	Burnet	43 min
May 21, 8:44 PM CDT	Tornado Warning	EWX	Burnet	31 min
May 21, 8:59 PM CDT	Tornado Warning	EWX	Williamson	31 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

Fort Worth, TX (KFWD), launched 12:00Z, 6.8 hours before the alert went out and 242 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: 87 J/kg
Mixed-layer CIN: -337 J/kg
Mixed-layer LCL: 1835 m above ground
0-6 km bulk shear: 56 kt
0-1 km storm-relative helicity: 203 m²/s²
0-3 km storm-relative helicity: 181 m²/s²
Significant tornado parameter: 0.0
Supercell composite: -0.0

Open this sounding in Storm Lab

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 20, 9:06 PM CDT	Mesoscale Discussion	SPC	Bowie, Camp, Cass, Cherokee, Gregg, Harrison and 7 more	114 min
May 21, 1:18 PM CDT	Mesoscale Discussion	SPC	Bandera, Bosque, Burnet, Coryell, Erath, Gillespie and 12 more	117 min
May 21, 3:53 PM CDT	Mesoscale Discussion	SPC	Bosque, Burnet, Coryell, Dallas, Ellis, Gillespie and 9 more	67 min
May 21, 5:42 PM CDT	Mesoscale Discussion	SPC	Bell, Blanco, Bosque, Burnet, Collin, Cooke and 28 more	2 hr

Nearby

Severe Thunderstorm Watches in Texas, 2011 Every 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.