Tornadoes · United States · Texas · 1991

F1 tornado, Lavaca County, Texas, May 4, 1991

This F1 tornado ran 5.0 miles across Lavaca County on May 4, 1991, touching down at 7:18 PM CDT and reaching 30 yards wide. It killed nobody, and did $50,000 to $500,000 of property damage.

The rating scale

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

  1. F040 to 72 mph

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

  2. F173 to 112 mphthis tornado

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

  3. F2113 to 157 mph

    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. F3158 to 206 mph

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

  5. F4207 to 260 mph

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

  6. F5261 to 318 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
F1
Date
May 4, 1991
Touchdown
7:18 PM CDT (00:18 UTC)
Path length
5.0 miles (8.0 km)
Path width
30 yards (27 m)
Deaths
0
Injuries
0
Property damage
$50,000 to $500,000
County
Lavaca County
Touchdown point
29.320, -97.150
Lift-off point
29.330, -97.070
Record number
434

The warnings

20 minutes of warning. NWS EWX issued a tornado warning for this county at 23:58 UTC, 20 minutes before the tornado touched down, in force until 01:00 UTC.

Issued (UTC)ExpiredProductOffice
23:58 UTC01:00 UTCTornado WarningEWX
00:57 UTC02:00 UTCTornado WarningEWX

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.

Corpus Christi, TX (KCRP), 00:00Z

0.3 hours before the tornado, 179 km from the path. May 5, 1991.

Skew-T log-pSkew-T log-p diagram, Corpus Christi, TX at 00:00Z on 1991-05-05Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 4154 joules per kilogram, CIN -72, lifted condensation level 618 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, Corpus Christi, TX at 00:00Z on 1991-05-05The 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 24 square meters per square second, 0 to 6 km bulk shear 50 knots.19395878Sfc1 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
4154 J/kg
Mixed-layer CIN
-72 J/kg
Surface CAPE
4670 J/kg
Mixed-layer LCL
618 m above ground
0-6 km bulk shear
50 kt
0-1 km bulk shear
15 kt
0-1 km storm-relative helicity
24 m²/s²
0-3 km storm-relative helicity
58 m²/s²
Significant tornado parameter
0.9
Supercell composite
3.6
0-3 km lapse rate
4.9 K/km

Open this sounding in Storm Lab

Corpus Christi, TX (KCRP), 12:00Z

11.7 hours after it, 179 km from the path. May 5, 1991.

Skew-T log-pSkew-T log-p diagram, Corpus Christi, TX at 12:00Z on 1991-05-05Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 2243 joules per kilogram, CIN -196, lifted condensation level 1446 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, Corpus Christi, TX at 12:00Z on 1991-05-05The 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 107 square meters per square second, 0 to 6 km bulk shear 47 knots.19395878Sfc1 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
2243 J/kg
Mixed-layer CIN
-196 J/kg
Surface CAPE
4782 J/kg
Mixed-layer LCL
1446 m above ground
0-6 km bulk shear
47 kt
0-1 km bulk shear
25 kt
0-1 km storm-relative helicity
107 m²/s²
0-3 km storm-relative helicity
2 m²/s²
Significant tornado parameter
0.0
Supercell composite
2.0
0-3 km lapse rate
5.1 K/km

Open this sounding in Storm Lab

The surface observations

Victoria Regional (VCT), 54 km from the path, in the two hours either side.

Time (UTC)Temp (°F)Dew point (°F)WindGust (kt)Pressure (mb)Weather
23:00 UTC8375180° 13 kt1008.8
00:00 UTC8175170° 11 kt1008.5
00:37 UTC180° 11 kt1008.8
01:00 UTC8176160° 10 kt1008.8DZ
02:00 UTC8076140° 5 kt1010.2

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

This ground now

The live radar over the trackEvery 1991 tornado in TexasEvery tornado in Texas since 1950Warnings in force in Texas nowThe forecast where you are

The other tornadoes of May 4, 1991

11 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
May 42:48 AM CDTF0Allen Parish, LA0.217$5,000 to $50,000
May 41:09 PM CDTF0Runnels, TX0.880
May 44:58 PM CDTF0Garvin, OK0.320
May 46:50 PM CDTF1Smith, TX0.210$5,000 to $50,000
May 47:31 PM CDTF0Washington, TX0.210
May 47:34 PM CDTF0Washington, TX0.210
May 48:03 PM CDTF0Washington, TX0.210
May 49:00 PM CDTF0Angelina, TX0.210
May 49:30 PM CDTF1Wharton, TX0.210$50,000 to $500,000
May 411:00 PM CDTF0Montgomery, TX0.210
May 411:05 PM CDTF0Brazoria, TX0.210$5,000 to $50,000

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.