Tornadoes · United States · Texas · 1977

F1 tornado, Comal County, Texas, April 13, 1977

This F1 tornado ran 0.5 miles across Comal County on April 13, 1977, touching down at 3:40 PM CST and reaching 40 yards wide. It killed nobody, and did $5,000 to $50,000 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
April 13, 1977
Touchdown
3:40 PM CST (21:40 UTC)
Path length
0.5 miles (0.8 km)
Path width
40 yards (37 m)
Deaths
0
Injuries
0
Property damage
$5,000 to $50,000
County
Comal County
Touchdown point
29.650, -98.220
Record number
127

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.

Victoria Regiona, TX (KVCT), 12:00Z

9.7 hours before the tornado, 156 km from the path. April 13, 1977.

Skew-T log-pSkew-T log-p diagram, Victoria Regiona, TX at 12:00Z on 1977-04-13Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 586 joules per kilogram, CIN -14, lifted condensation level 675 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, Victoria Regiona, TX at 12:00Z on 1977-04-13The 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 73 square meters per square second, 0 to 6 km bulk shear 15 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
586 J/kg
Mixed-layer CIN
-14 J/kg
Surface CAPE
530 J/kg
Mixed-layer LCL
675 m above ground
0-6 km bulk shear
15 kt
0-1 km bulk shear
16 kt
0-1 km storm-relative helicity
73 m²/s²
0-3 km storm-relative helicity
138 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
6.1 K/km

Open this sounding in Storm Lab

Victoria Regiona, TX (KVCT), 00:00Z

2.3 hours after it, 156 km from the path. April 14, 1977.

Skew-T log-pSkew-T log-p diagram, Victoria Regiona, TX at 00:00Z on 1977-04-14Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 669 joules per kilogram, CIN -5, lifted condensation level 792 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, Victoria Regiona, TX at 00:00Z on 1977-04-14The 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 29 square meters per square second, 0 to 6 km bulk shear 29 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
669 J/kg
Mixed-layer CIN
-5 J/kg
Surface CAPE
1875 J/kg
Mixed-layer LCL
792 m above ground
0-6 km bulk shear
29 kt
0-1 km bulk shear
5 kt
0-1 km storm-relative helicity
29 m²/s²
0-3 km storm-relative helicity
43 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.6
0-3 km lapse rate
6.3 K/km

Open this sounding in Storm Lab

The surface observations

Randolph Afb (RND), 15 km from the path, in the two hours either side.

Time (UTC)Temp (°F)Dew point (°F)WindGust (kt)Pressure (mb)Weather
20:00 UTC7463160° 8 kt1015.9
20:09 UTC70° 9 kt1015.9SHRA
20:25 UTC716440° 6 kt1015.2+TSRA
20:33 UTC100° 14 kt201015.9+TSRA FZFG
20:40 UTC120° 16 kt221015.9+TSRA FZFG
21:00 UTC6661100° 11 kt1015.9TSRA FG
21:03 UTC100° 10 kt1015.9+TSRA
21:20 UTC150° 8 kt1015.9+TSRA
22:00 UTC6662100° 9 kt1015.2TSRA
22:47 UTC100° 9 kt1014.9SHRA
23:00 UTC6762100° 6 kt1014.9-SHRA
23:23 UTC80° 6 kt1015.2

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

This ground now

The live radar over the trackEvery 1977 tornado in TexasEvery tornado in Texas since 1950Warnings in force in Texas nowThe forecast where you are

The other tornadoes of April 13, 1977

1 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
April 132:10 PM MSTF2Crowley, CO5.130$500 to $5,000

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.