Tornadoes · United States · Texas · 2011

EF2 tornado, (P07)Sanderson, Texas, April 21, 2011

This EF2 tornado ran 7.8 miles across Terrell County on April 21, 2011, touching down at 6:45 PM CDT and reaching 800 yards wide. It killed nobody, and did $100,000 of property damage.

The rating scale

Tracks are drawn in the color of the rating. The Enhanced Fujita scale rates the damage rather than measuring the wind: the speeds are what that damage is taken to imply.

  1. EF065 to 85 mph

    Light damage. Surface peeled off some roofs, gutters and siding damaged, branches broken, shallow-rooted trees pushed over.

  2. EF186 to 110 mph

    Moderate damage. Roofs badly stripped, mobile homes overturned or badly damaged, exterior doors lost, windows broken.

  3. EF2111 to 135 mphthis tornado

    Considerable damage. Roofs torn off well-built houses, frame homes shifted on their foundations, mobile homes destroyed, large trees snapped or uprooted, cars lifted off the ground.

  4. EF3136 to 165 mph

    Severe damage. Whole stories of well-built houses destroyed, large buildings badly damaged, trains overturned, trees debarked, heavy cars lifted and thrown.

  5. EF4166 to 200 mph

    Devastating damage. Well-built houses leveled, structures with weak foundations moved some distance, cars thrown and large missiles generated.

  6. EF5over 200 mph

    Incredible damage. Strong frame houses swept off their foundations, car-sized missiles thrown more than 100 meters, steel-reinforced concrete badly damaged, high-rise buildings deformed.

  7. Unrated

    The survey recorded a tornado but could not put a number on it, most often because it crossed open country and damaged nothing a rating can be read from.

The record

Rating
EF2
Date
April 21, 2011
Touchdown
6:45 PM CDT (23:45 UTC)
Lifted
6:50 PM CDT (23:50 UTC)
On the ground
5 minutes
Path length
7.8 miles (12.6 km)
Path width
800 yards (732 m)
Deaths
0
Injuries
0
Property damage
$100,000
County
Terrell County
Touchdown point
30.204, -102.445
Lift-off point
30.158, -102.325
Record number
1104211745-01

What the Weather Service recorded

Isolated thunderstorms developed along a weak cold front April 20, near the Lower Trans Pecos and Stockton Plateau. During the afternoon hours the next day, severe thunderstorms develop within significant low level moisture just ahead of a dryline over Terrell and Pecos Counties. Backed surface winds across Terrell County supported a low level shear near storm environment sufficient enough to produce brief tornadoes. One supercell produced at least 2 tornadoes as it moved across portions of south central Pecos County and into Terrell County.

Tornado damage was reported near Sanderson at approximately 17:45 CST. Several cedar trees were destroyed as the tornado tracked east southeast. A home and barn were also destroyed by the tornado. Spotter reports indicate the tornado was 1/2 mile wide and travelled approximately 9 miles.

From NOAA NCEI's Storm Events Database, the narrative the local forecast office wrote for Storm Data.

The warnings

58 minutes of warning. NWS MAF issued a tornado warning for this county at 22:47 UTC, 58 minutes before the tornado touched down, in force until 23:45 UTC.

The county was under a severe thunderstorm watch, issued at 20:05 UTC and running to 03:00 UTC.

Issued (UTC)ExpiredProductOffice
20:05 UTC03:00 UTCSevere Thunderstorm WatchMAF
21:18 UTC22:15 UTCTornado WarningMAF
22:47 UTC23:45 UTCTornado WarningMAF
23:45 UTC00:45 UTCTornado WarningMAF
00:44 UTC01:30 UTCTornado WarningMAF
01:14 UTC01:41 UTCSevere Thunderstorm WarningMAF

Every warning and watch covering the touchdown point that day, from the Iowa Environmental Mesonet's archive of National Weather Service products. Lead time is measured from the issue of the warning in force to the touchdown time in the database, both of which were recorded to the minute by different people.

The air that afternoon

The radiosonde launches on either side of the tornado, from the nearest station that was launching then, drawn and analyzed the way Storm Lab does: the same diagram, the same parcel and shear definitions SPC's mesoanalysis uses.

Del Rio, TX (KDRT), 12:00Z

11.8 hours before the tornado, 174 km from the path. April 21, 2011.

Skew-T log-pSkew-T log-p diagram, Del Rio, TX at 12:00Z on 2011-04-21Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 2808 joules per kilogram, CIN -107, lifted condensation level 643 meters above ground. Wind barbs in knots down the right edge.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. The warm shading is its CAPE, the cool shading the inhibition it has to break through.
HodographHodograph, Del Rio, TX at 12:00Z on 2011-04-21The wind through the lowest 10 kilometers as a curve, rings every 10 meters per second labeled in knots. Zero to 1 km storm-relative helicity 176 square meters per square second, 0 to 6 km bulk shear 28 knots.1939Sfc1 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. RM and LM are the right and left moving storms Bunkers' method gives; the shaded area is the 0 to 1 km storm-relative helicity.
Mixed-layer CAPE
2808 J/kg
Mixed-layer CIN
-107 J/kg
Surface CAPE
2497 J/kg
Mixed-layer LCL
643 m above ground
0-6 km bulk shear
28 kt
0-1 km bulk shear
22 kt
0-1 km storm-relative helicity
176 m²/s²
0-3 km storm-relative helicity
223 m²/s²
Significant tornado parameter
0.7
Supercell composite
4.7
0-3 km lapse rate
4.7 K/km

Open this sounding in Storm Lab

Del Rio, TX (KDRT), 00:00Z

0.2 hours after it, 174 km from the path. April 22, 2011.

Skew-T log-pSkew-T log-p diagram, Del Rio, TX at 00:00Z on 2011-04-22Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 2280 joules per kilogram, CIN -76, lifted condensation level 2009 meters above ground. Wind barbs in knots down the right edge.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. The warm shading is its CAPE, the cool shading the inhibition it has to break through.
HodographHodograph, Del Rio, TX at 00:00Z on 2011-04-22The wind through the lowest 10 kilometers as a curve, rings every 10 meters per second labeled in knots. Zero to 1 km storm-relative helicity 36 square meters per square second, 0 to 6 km bulk shear 13 knots.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. RM and LM are the right and left moving storms Bunkers' method gives; the shaded area is the 0 to 1 km storm-relative helicity.
Mixed-layer CAPE
2280 J/kg
Mixed-layer CIN
-76 J/kg
Surface CAPE
2692 J/kg
Mixed-layer LCL
2009 m above ground
0-6 km bulk shear
13 kt
0-1 km bulk shear
16 kt
0-1 km storm-relative helicity
36 m²/s²
0-3 km storm-relative helicity
155 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
7.4 K/km

Open this sounding in Storm Lab

The surface observations

Dryden (6R6), 22 km from the path, in the two hours either side.

Time (UTC)Temp (°F)Dew point (°F)WindGust (kt)Pressure (mb)Weather
21:53 UTC9363100° 14 kt301007.5
22:53 UTC8864100° 16 kt281006.8
23:53 UTC8663120° 22 kt381005.4
00:10 UTC73.466.210° 26 kt501007.8SQ
00:18 UTC7764.4320° 14 kt381008.8
00:53 UTC736450° 21 kt321008.8
01:00 UTC73.464.460° 20 kt291009.5

From the Iowa Environmental Mesonet's archive of airport observations.

The radar

The Midland/Odessa radar (KMAF), 197 km away, was scanning. The volume nearest the touchdown began at 23:44 UTC.

Open the radar archive at this moment, over the track

Reflectivity and velocity, decoded from the Level II archive in the browser. Volumes take a few seconds to open the first time.

What was reported nearby

Local storm reports within 60 km of the path, in the three hours either side.

Time (UTC)ReportWhereCountyRemark
21:20 UTCHAIL 1.7525 Se Fort StocktonPecos, TXREPORTED ALONG HIGHWAY 285.
23:04 UTCTSTM WND GST 58DrydenTerrell, TX50 KNOT WIND GUST MEASURED AT DRYDEN ASOS.

From the Iowa Environmental Mesonet's archive of National Weather Service local storm reports.

This ground now

The live radar over the trackEvery 2011 tornado in TexasEvery tornado in Texas since 1950Warnings in force in Texas nowThe forecast where you are

The other tornadoes of April 21, 2011

4 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
April 215:51 PM CDTEF0Pecos, TX3.8300
April 216:18 PM CDTEF0Pecos, TX8.1200
April 218:52 PM CDTEF1Jones, TX5.0200
April 218:55 PM CDTEF0Jones, TX0.1100

What this means

Ratings are the survey's, read off the damage rather than measured; the rating scale is above. Tornado counts rise through the record as reporting improved, so a year in the 1950s is not comparable with one today except for the strongest tornadoes, which were always noticed.

Sources

NOAA Storm Prediction Center tornado database, 1950-2025, the official record kept by NOAA's Storm Prediction Center.