Tornadoes · United States · Texas · 1997

F0 tornado, Pennington to Nogalus, Texas, April 4, 1997

From Pennington to Nogalus, this F0 tornado ran 0.1 miles across Trinity County on April 4, 1997, touching down at 2:50 PM CST and reaching 20 yards wide. It killed nobody.

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 mphthis tornado

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

  2. F173 to 112 mph

    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
F0
Date
April 4, 1997
Touchdown
2:50 PM CST (20:50 UTC)
Path length
0.1 miles (0.2 km)
Path width
20 yards (18 m)
Deaths
0
Injuries
0
County
Trinity County
Touchdown point
31.270, -95.120
Lift-off point
31.270, -95.120
Record number
80

What the Weather Service recorded

DPS reported tornado south of Pennington. Trees were blown down.

Sheriff reported tornado at Nogalus Prairie near Centralia. No damage confirmed.

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

The warnings

45 minutes of warning. NWS HGX issued a tornado warning for this county at 20:05 UTC, 45 minutes before the tornado touched down, in force until 21:05 UTC.

Issued (UTC)ExpiredProductOffice
20:05 UTC21:05 UTCTornado WarningHGX

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 forecast that day

The Storm Prediction Center had this point in a Moderate Risk. The outlook in force was issued at 06:46 UTC.

SPC's Day 1 convective outlook as it stood when the tornado began, read at the touchdown point. The same archive is on the radar archive.

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.

Shreveport, LA (KSHV), 12:00Z

8.8 hours before the tornado, 187 km from the path. April 4, 1997.

Skew-T log-pSkew-T log-p diagram, Shreveport, LA at 12:00Z on 1997-04-04Temperature 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 -38313, lifted condensation level 533 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, Shreveport, LA at 12:00Z on 1997-04-04The 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 154 square meters per square second, 0 to 6 km bulk shear 21 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
0 J/kg
Mixed-layer CIN
-38313 J/kg
Surface CAPE
0 J/kg
Mixed-layer LCL
533 m above ground
0-6 km bulk shear
21 kt
0-1 km bulk shear
38 kt
0-1 km storm-relative helicity
154 m²/s²
0-3 km storm-relative helicity
237 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.3
0-3 km lapse rate
4.7 K/km

Open this sounding in Storm Lab

Shreveport, LA (KSHV), 00:00Z

3.2 hours after it, 187 km from the path. April 5, 1997.

Skew-T log-pSkew-T log-p diagram, Shreveport, LA at 00:00Z on 1997-04-05Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 94 joules per kilogram, CIN -95, lifted condensation level 621 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, Shreveport, LA at 00:00Z on 1997-04-05The 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 206 square meters per square second, 0 to 6 km bulk shear 46 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
94 J/kg
Mixed-layer CIN
-95 J/kg
Surface CAPE
7 J/kg
Mixed-layer LCL
621 m above ground
0-6 km bulk shear
46 kt
0-1 km bulk shear
34 kt
0-1 km storm-relative helicity
206 m²/s²
0-3 km storm-relative helicity
332 m²/s²
Significant tornado parameter
0.0
Supercell composite
1.5
0-3 km lapse rate
4.2 K/km

Open this sounding in Storm Lab

The surface observations

Lufkin/Angelina Co. (LFK), 35 km from the path, in the two hours either side.

Time (UTC)Temp (°F)Dew point (°F)WindGust (kt)Pressure (mb)Weather
18:50 UTC75.269.8180° 11 kt1006.1
19:50 UTC75.271.6170° 11 kt1003.7
19:54 UTC75.271.6170° 10 kt171003.4
20:06 UTC75.271.6170° 17 kt231003
20:15 UTC71.671.6160° 17 kt311003
20:23 UTC71.669.8190° 12 kt221003
20:51 UTC71.671.6220° 11 kt1003.7BR
21:50 UTC73.471.6180° 8 kt1002.4BR
22:21 UTC73.471.6120° 4 kt1001.4
22:37 UTC73.471.6150° 8 kt1001.4

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

The radar

The Shreveport radar (KSHV), 178 km away, was scanning. The volume nearest the touchdown began at 20:49 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.

This ground now

The live radar over the trackEvery 1997 tornado in TexasEvery tornado in Texas since 1950Warnings in force in Texas nowThe forecast where you are

The other tornadoes of April 4, 1997

12 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
April 43:25 AM CSTF1Cameron, TX0.5100$40,000
April 44:30 AM CSTF0Cameron, TX0.150
April 411:04 AM CSTF0Tom Green, TX0.123
April 41:50 PM CSTF1Houston, TX0.350$40,000
April 42:05 PM CSTF0Houston, TX0.223$10,000
April 42:15 PM CSTF1Houston, TX0.333$40,000
April 42:30 PM CSTF0Trinity, TX0.120$10,000
April 44:45 PM CSTF1Webster Parish, LA20.0100$200,000
April 43:45 PM MSTF1Kimball, NE1.050
April 44:50 PM CSTF0Denton, TX0.130$10,000
April 45:20 PM CSTF1Columbia, AR7.0200$200,000
April 48:40 PM CSTF0Pushmataha, OK0.550$100,000

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.