Alert archive / Texas / Severe Thunderstorm Watches in 2021

Severe Thunderstorm Watch 511

September 30, 202122 counties in Texas

The Storm Prediction Center issued this severe thunderstorm watch at Sep 30, 2021, 12:44 PM CDT for 22 counties in Texas. It was in force for 8 hr.

The area

The outline as issued.

The facts

Issued: Sep 30, 2021, 12:44 PM CDT (17:44 UTC)
Expired: Sep 30, 2021, 8:15 PM CDT
In force: 8 hr
Issued by: the Storm Prediction Center
Largest hail expected: 1.5 in
Strongest gust expected: 55 kt

All 22 counties

Borden County, TX, Brewster County, TX, Coke County, TX, Crane County, TX, Crockett County, TX, Fisher County, TX, Glasscock County, TX, Howard County, TX, Irion County, TX, Jones County, TX, Midland County, TX, Mitchell County, TX, Nolan County, TX, Pecos County, TX, Reagan County, TX, Runnels County, TX, Scurry County, TX, Sterling County, TX, Taylor County, TX, Terrell County, TX, Tom Green County, TX, Upton County, TX

The radar

The San Angelo radar (KSJT), 66 km from the middle of the area, began a volume at 17:44 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: 10%
One or more EF2 to EF5 tornadoes: 2%
Ten or more severe wind reports: 40%
One or more gusts of 65 knots or more: 20%
Ten or more severe hail reports: 40%
One or more hailstones of 2 inches or more: 20%
Six or more combined severe hail and wind reports: 70%

Warnings issued inside it

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

Issued	Product	Office	Counties	Lasted
Sep 30, 1:14 PM CDT	Severe Thunderstorm Warning	MAF	Howard, Mitchell	46 min
Sep 30, 1:44 PM CDT	Flash Flood Warning Considerable damage threat	SJT	Nolan	3 hr
Sep 30, 1:59 PM CDT	Severe Thunderstorm Warning	MAF	Borden, Howard, Mitchell, Scurry	61 min
Sep 30, 2:06 PM CDT	Severe Thunderstorm Warning	SJT	Nolan	39 min
Sep 30, 2:27 PM CDT	Severe Thunderstorm Warning	SJT	Nolan	48 min
Sep 30, 3:08 PM CDT	Flash Flood Warning Considerable damage threat	SJT	Nolan	3 hr
Sep 30, 3:12 PM CDT	Severe Thunderstorm Warning	MAF	Pecos, Terrell	63 min
Sep 30, 3:29 PM CDT	Flash Flood Warning Considerable damage threat	SJT	Callahan, Jones, Shackelford, Taylor	3 hr
Sep 30, 3:31 PM CDT	Severe Thunderstorm Warning	MAF	Brewster	44 min
Sep 30, 3:45 PM CDT	Severe Thunderstorm Warning	SJT	Fisher, Nolan, Taylor	28 min
Sep 30, 3:51 PM CDT	Severe Thunderstorm Warning	SJT	Jones, Taylor	39 min
Sep 30, 4:03 PM CDT	Severe Thunderstorm Warning	MAF	Brewster, Pecos	57 min
Sep 30, 4:10 PM CDT	Severe Thunderstorm Warning	MAF	Pecos, Terrell	65 min
Sep 30, 4:53 PM CDT	Severe Thunderstorm Warning	MAF	Brewster, Pecos, Terrell	52 min
Sep 30, 7:08 PM CDT	Severe Thunderstorm Warning Considerable damage threat	MAF	Terrell	32 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

Midland Regional, TX (KMAF), launched 12:00Z, 5.7 hours before the alert went out and 110 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: 1726 J/kg
Mixed-layer CIN: -108 J/kg
Mixed-layer LCL: 1297 m above ground
0-6 km bulk shear: 6 kt
0-1 km storm-relative helicity: -13 m²/s²
0-3 km storm-relative helicity: 8 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

703 
WWUS20 KWNS 301742
SEL1  
SPC WW 301742
TXZ000-010200-

URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 511
NWS Storm Prediction Center Norman OK
1245 PM CDT Thu Sep 30 2021

The NWS Storm Prediction Center has issued a

* Severe Thunderstorm Watch for portions of 
  West central and southwest Texas

* Effective this Thursday afternoon and evening from 1245 PM
  until 900 PM CDT.

* Primary threats include...
  Scattered damaging wind gusts to 65 mph possible
  Scattered large hail events to 1.5 inches in diameter possible

SUMMARY...Thunderstorms are expected to increase in coverage and
intensity this afternoon along and ahead of a surface cold front. 
The storm environment will favor a mix of multicell clusters and
some supercells capable of producing large hail up to about 1.5 to
1.75" diameter and outflow wind gusts up to about 65 mph.

The severe thunderstorm watch area is approximately along and 65
statute miles east and west of a line from 50 miles northwest of
Abilene TX to 40 miles west southwest of Dryden TX. For a complete
depiction of the watch see the associated watch outline update
(WOUS64 KWNS WOU1).

PRECAUTIONARY/PREPAREDNESS ACTIONS...

REMEMBER...A Severe Thunderstorm Watch means conditions are
favorable for 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. Severe thunderstorms can and occasionally do produce
tornadoes.

&&

AVIATION...A few severe thunderstorms with hail surface and aloft to
1.5 inches. Extreme turbulence and surface wind gusts to 55 knots. A
few cumulonimbi with maximum tops to 550. Mean storm motion vector
26020.

...Thompson

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Sep 30, 10:38 AM CDT	Mesoscale Discussion	SPC	Brewster, Coke, Crane, Culberson, Ector, Fisher and 18 more	3 hr
Sep 30, 3:01 PM CDT	Mesoscale Discussion	SPC	Brewster, Coke, Crockett, Culberson, Glasscock, Irion and 11 more	119 min
Sep 30, 6:08 PM CDT	Mesoscale Discussion	SPC	Crockett, Irion, Reagan, Terrell, Tom Green	2 hr

Nearby

Severe Thunderstorm Watches in Texas, 2021 Every severe thunderstorm watch in 2021

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.