Alert archive / Texas / Tornado Watches in 2018

Tornado Watch 444

December 26, 201823 counties in Texas

The Storm Prediction Center issued this tornado watch at Dec 26, 2018, 5:48 PM CST for 23 counties in Texas. It was in force for 8 hr.

The area

The outline as issued.

The facts

Issued
Dec 26, 2018, 5:48 PM CST (23:48 UTC)
Expired
Dec 27, 2018, 2:00 AM CST
In force
8 hr
Issued by
the Storm Prediction Center
Largest hail expected
1 in
Strongest gust expected
60 kt
All 23 counties

Atascosa County, TX, Bandera County, TX, Bastrop County, TX, Bexar County, TX, Blanco County, TX, Caldwell County, TX, Comal County, TX, Edwards County, TX, Frio County, TX, Gillespie County, TX, Gonzales County, TX, Guadalupe County, TX, Hays County, TX, Kendall County, TX, Kerr County, TX, Kinney County, TX, Lee County, TX, Medina County, TX, Real County, TX, Travis County, TX, Uvalde County, TX, Wilson County, TX, Zavala County, TX

The radar

The Austin/San Antonio radar (KEWX), 51 km from the middle of the area, began a volume at 23:51 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
60%
One or more EF2 to EF5 tornadoes
20%
Ten or more severe wind reports
60%
One or more gusts of 65 knots or more
20%
Ten or more severe hail reports
20%
One or more hailstones of 2 inches or more
10%
Six or more combined severe hail and wind reports
80%

Warnings issued inside it

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

IssuedProductOfficeCountiesLasted
Dec 26, 6:09 PM CSTSevere Thunderstorm WarningEWXEdwards, Kinney, Val Verde66 min
Dec 26, 7:06 PM CSTSevere Thunderstorm WarningEWXEdwards, Kinney, Val Verde54 min
Dec 26, 7:10 PM CSTSevere Thunderstorm WarningEWXEdwards, Kerr, Real65 min
Dec 26, 8:01 PM CSTSevere Thunderstorm WarningEWXBandera, Edwards, Kerr, Kinney, Real, Uvalde78 min
Dec 26, 10:43 PM CSTSevere Thunderstorm WarningEWXComal, Hays32 min
Dec 27, 12:38 AM CSTFlash Flood WarningEWXHays, Travis, Williamson3 hr

Discussions around it

SPC mesoscale discussions over the same counties from four hours before the watch to its end.

The nearest sounding before it

Del Rio, TX (KDLF), launched 12:00Z, 11.8 hours before the alert went out and 230 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, Del Rio, TX at 12:00Z on 2018-12-26Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 609 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, Del Rio, TX at 12:00Z on 2018-12-26The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 233 square meters per square second.1939587897Sfc1 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
609 J/kg
Mixed-layer CIN
-68 J/kg
Mixed-layer LCL
560 m above ground
0-6 km bulk shear
50 kt
0-1 km storm-relative helicity
233 m²/s²
0-3 km storm-relative helicity
391 m²/s²
Significant tornado parameter
0.6
Supercell composite
2.9

Open this sounding in Storm Lab

The text

As transmitted.

006 
WWUS20 KWNS 262346
SEL4  
SPC WW 262346
TXZ000-270800-

URGENT - IMMEDIATE BROADCAST REQUESTED
Tornado Watch Number 444
NWS Storm Prediction Center Norman OK
545 PM CST Wed Dec 26 2018

The NWS Storm Prediction Center has issued a

* Tornado Watch for portions of 
  South-central Texas

* Effective this Wednesday afternoon and Thursday morning from
  545 PM until 200 AM CST.

* Primary threats include...
  A few tornadoes likely
  Scattered damaging wind gusts to 70 mph likely
  Isolated large hail events to 1 inch in diameter possible

SUMMARY...Storms will continue to increase this evening, initially
across the Edwards Plateau. Damaging winds and some severe hail will
be possible, but a few tornadoes will also be possible, especially
as storms encounter richer moisture and stronger low-level shear
toward the Hill County/I-35 general vicinity later this evening into
the overnight.

The tornado watch area is approximately along and 95 statute miles
east and west of a line from 60 miles west northwest of Austin TX to
45 miles south of Hondo TX. For a complete depiction of the watch
see the associated watch outline update (WOUS64 KWNS WOU4).

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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 441...WW 442...WW 443...

AVIATION...Tornadoes and a few severe thunderstorms with hail
surface and aloft to 1 inch. Extreme turbulence and surface wind
gusts to 60 knots. A few cumulonimbi with maximum tops to 500. Mean
storm motion vector 23035.

...Guyer

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Dec 26, 11:33 AM CSTMesoscale DiscussionSPCBailey, Borden, Briscoe, Castro, Coke, Crockett and 24 more117 min
Dec 26, 12:28 PM CSTMesoscale DiscussionSPCArcher, Baylor, Brown, Callahan, Coleman, Comanche and 22 more2 hr
Dec 26, 12:44 PM CSTSevere Thunderstorm WatchSPCArmstrong, Borden, Briscoe, Carson, Castro, Childress and 40 more6 hr
Dec 26, 2:11 PM CSTTornado WatchSPCBell, Bosque, Brown, Burnet, Callahan, Coleman and 29 more10 hr
Dec 26, 3:21 PM CSTMesoscale DiscussionSPCArmstrong, Borden, Briscoe, Castro, Childress, Coke and 34 more84 min
Dec 26, 4:43 PM CSTMesoscale DiscussionSPCArcher, Baylor, Bell, Blanco, Bosque, Brown and 42 more2 hr
Dec 26, 4:58 PM CSTMesoscale DiscussionSPCArcher, Baylor, Bell, Blanco, Bosque, Brown and 42 more62 min
Dec 26, 5:06 PM CSTSevere Thunderstorm WatchSPCArcher, Baylor, Clay, Foard, Hardeman, Knox and 2 more4 hr

Nearby

Tornado Watches in Texas, 2018Every tornado watch in 2018

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.