Tornadoes · United States · Texas · 1977

F1 tornado, Howard County, Texas, May 20, 1977

This F1 tornado ran 0.5 miles across Howard County on May 20, 1977, touching down at 3:52 PM CDT and reaching 20 yards wide. It killed nobody, and did under $50 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 20, 1977
Touchdown
3:52 PM CDT (20:52 UTC)
Path length
0.5 miles (0.8 km)
Path width
20 yards (18 m)
Deaths
0
Injuries
0
Property damage
under $50
County
Howard County
Touchdown point
32.170, -101.580
Record number
330

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.

Midland Regional, TX (KMAF), 12:00Z

8.9 hours before the tornado, 63 km from the path. May 20, 1977.

Skew-T log-pSkew-T log-p diagram, Midland Regional, TX at 12:00Z on 1977-05-20Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 1880 joules per kilogram, CIN -7, lifted condensation level 709 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, Midland Regional, TX at 12:00Z on 1977-05-20The 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 94 square meters per square second, 0 to 6 km bulk shear 47 knots.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. 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
1880 J/kg
Mixed-layer CIN
-7 J/kg
Surface CAPE
2353 J/kg
Mixed-layer LCL
709 m above ground
0-6 km bulk shear
47 kt
0-1 km bulk shear
16 kt
0-1 km storm-relative helicity
94 m²/s²
0-3 km storm-relative helicity
112 m²/s²
Significant tornado parameter
0.9
Supercell composite
4.5
0-3 km lapse rate
6.6 K/km

Open this sounding in Storm Lab

Midland Regional, TX (KMAF), 00:00Z

3.1 hours after it, 63 km from the path. May 21, 1977.

Skew-T log-pSkew-T log-p diagram, Midland Regional, TX at 00:00Z on 1977-05-21Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 1019 joules per kilogram, CIN -34, lifted condensation level 2278 meters above ground. Wind barbs in knots down the right edge.LCLEL10008507005003002001001 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, Midland Regional, TX at 00:00Z on 1977-05-21The 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 -13 square meters per square second, 0 to 6 km bulk shear 63 knots.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. 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
1019 J/kg
Mixed-layer CIN
-34 J/kg
Surface CAPE
1827 J/kg
Mixed-layer LCL
2278 m above ground
0-6 km bulk shear
63 kt
0-1 km bulk shear
19 kt
0-1 km storm-relative helicity
-13 m²/s²
0-3 km storm-relative helicity
23 m²/s²
Significant tornado parameter
0.0
Supercell composite
-0.1
0-3 km lapse rate
9.5 K/km

Open this sounding in Storm Lab

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 May 20, 1977

25 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
May 2011:10 AM CDTF1Terry, TX2.030under $50
May 2011:30 AM CDTF0, SD0.110
May 2011:55 AM CDTF1Hockley, TX1.550under $50
May 201:09 PM CDTF1Hale, TX1.030under $50
May 202:45 PM CDTF1Hitchcock, NE0.120$5,000 to $50,000
May 202:58 PM CDTF1Briscoe, TX2.030under $50
May 203:20 PM CDTF3Jackson, OK10.48803$500,000 to $5 million
May 204:28 PM CDTF1Donley, TX2.030under $50
May 204:35 PM CDTF1Major, OK5.1100$5,000 to $50,000
May 204:43 PM CDTF1Grady, OK2.590$5,000 to $50,000
May 205:47 PM CDTF2Caddo, OK13.31,100$50,000 to $500,000
May 206:10 PM CDTF2Caddo, OK7.81,760$50,000 to $500,000
May 206:14 PM CDTF0Wheeler, TX1.020
May 206:38 PM CDTF3Tillman, OK1.5200$50,000 to $500,000
May 207:00 PM CDTF2Kiowa, OK3.6100$5,000 to $50,000
May 207:00 PM CDTF2Wilbarger, TX7.310$500 to $5,000
May 207:15 PM CDTF1Garfield, OK4.1100$5,000 to $50,000
May 207:40 PM CDTF2Oklahoma, OK14.9400$500,000 to $5 million
May 208:11 PM CDTF3Oklahoma, OK9.9400$50,000 to $500,000
May 208:20 PM CDTF2Logan, OK1.9100$50,000 to $500,000
May 208:30 PM CDTF1Logan, OK1.9100$5,000 to $50,000
May 208:45 PM CDTF1Grant, OK0.110$50,000 to $500,000
May 2010:00 PM CDTF1Wichita, TX0.110
May 2010:10 PM CDTF1Taylor, TX0.110
May 2012:30 AM CDTF1Garvin, OK2.750$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.