Tornadoes · United States · Kentucky · 1978

F1 tornado, Letcher County, Kentucky, May 12, 1978

This F1 tornado ran 14.4 miles across Letcher County on May 12, 1978, touching down at 10:45 PM EDT and reaching 400 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 12, 1978
Touchdown
10:45 PM EDT (02:45 UTC)
Path length
14.4 miles (23.2 km)
Path width
400 yards (366 m)
Deaths
0
Injuries
0
Property damage
$50,000 to $500,000
County
Letcher County
Touchdown point
37.120, -86.700
Lift-off point
37.180, -86.450
Record number
259

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.

Nashville Metro, TN (KBNA), 00:00Z

2.8 hours before the tornado, 113 km from the path. May 13, 1978.

Skew-T log-pSkew-T log-p diagram, Nashville Metro, TN at 00:00Z on 1978-05-13Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 480 joules per kilogram, CIN -56, lifted condensation level 849 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, Nashville Metro, TN at 00:00Z on 1978-05-13The 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 310 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
480 J/kg
Mixed-layer CIN
-56 J/kg
Surface CAPE
1381 J/kg
Mixed-layer LCL
849 m above ground
0-6 km bulk shear
47 kt
0-1 km bulk shear
30 kt
0-1 km storm-relative helicity
310 m²/s²
0-3 km storm-relative helicity
408 m²/s²
Significant tornado parameter
0.9
Supercell composite
10.6
0-3 km lapse rate
6.1 K/km

Open this sounding in Storm Lab

Nashville Metro, TN (KBNA), 12:00Z

9.2 hours after it, 113 km from the path. May 13, 1978.

Skew-T log-pSkew-T log-p diagram, Nashville Metro, TN at 12:00Z on 1978-05-13Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 0 joules per kilogram, CIN -13896, lifted condensation level 1256 meters above ground. Wind barbs in knots down the right edge.LCL10008507005003002001001 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, Nashville Metro, TN at 12:00Z on 1978-05-13The 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 190 square meters per square second, 0 to 6 km bulk shear 75 knots.1939587897117Sfc1 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
0 J/kg
Mixed-layer CIN
-13896 J/kg
Surface CAPE
0 J/kg
Mixed-layer LCL
1256 m above ground
0-6 km bulk shear
75 kt
0-1 km bulk shear
43 kt
0-1 km storm-relative helicity
190 m²/s²
0-3 km storm-relative helicity
197 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
5.9 K/km

Open this sounding in Storm Lab

The surface observations

Bowling Green (BWG), 25 km from the path, in the two hours either side.

Time (UTC)Temp (°F)Dew point (°F)WindGust (kt)Pressure (mb)Weather
01:00 UTC7165170° 17 kt1006.1
02:00 UTC7264180° 12 kt251004.7TS
03:00 UTC69.864.4170° 15 ktTS
04:00 UTC6965180° 16 kt1002.4
04:10 UTC180° 17 kt1001.4TS
04:30 UTC190° 16 kt1001.7TSRA

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

This ground now

The live radar over the trackEvery 1978 tornado in KentuckyEvery tornado in Kentucky since 1950Warnings in force in Kentucky nowThe forecast where you are

The other tornadoes of May 12, 1978

25 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
May 121:35 AM CDTF1Caddo Parish, LA4.053$50,000 to $500,000
May 122:00 PM CDTF1Polk, MO3.6100$5,000 to $50,000
May 122:14 PM CDTF1Benton, AR3.050$5,000 to $50,000
May 123:15 PM CDTF2Pulaski, MO19.54004$500,000 to $5 million
May 124:00 PM CDTF1Dent, MO0.110$5,000 to $50,000
May 124:05 PM CDTF1Saint Louis, MO0.550$50,000 to $500,000
May 124:30 PM CDTF1Kaufman, TX0.110
May 124:50 PM CDTF2Macoupin, IL34.17001$50,000 to $500,000
May 125:10 PM CDTF2Stone, AR12.1200$50,000 to $500,000
May 126:00 PM CDTF1Jefferson, MO4.5200$50,000 to $500,000
May 126:20 PM CDTF1Daviess, MO1.02001$50,000 to $500,000
May 126:45 PM CDTF1Hempstead, AR2.0772$5,000 to $50,000
May 127:00 PM CDTF2Macon, IL7.67003$50,000 to $500,000
May 127:00 PM CDTF0Grant, AR0.327
May 127:58 PM CDTF0Arkansas, AR0.350$500 to $5,000
May 128:00 PM CDTF2Trigg, KY15.8800$500,000 to $5 million
May 128:25 PM CDTF3Trigg, KY9.580017$500,000 to $5 million
May 129:05 PM CDTF0Houston, TX0.110
May 129:05 PM CDTF0Houston, TX0.110
May 129:05 PM CDTF0Houston, TX0.110
May 129:20 PM ESTF1Pike, IN1.540$50,000 to $500,000
May 129:35 PM CDTF1Pontotoc, MS14.520018$50,000 to $500,000
May 1210:25 PM CDTF2Coahoma, MS33.4100$5 million to $50 million
May 1212:15 AM CDTF1Morgan, AL3.610011$50,000 to $500,000
May 1212:35 AM CDTF1Marshall, AL8.0200

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.