Tornadoes · United States · Texas · 1998

F1 tornado, La Porte, Texas, September 11, 1998

This F1 tornado ran 0.2 miles across Harris County on September 11, 1998, touching down at 4:32 AM CDT and reaching 50 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 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
September 11, 1998
Touchdown
4:32 AM CDT (09:32 UTC)
Path length
0.2 miles (0.3 km)
Path width
50 yards (46 m)
Deaths
0
Injuries
0
County
Harris County
Touchdown point
29.670, -95.020
Lift-off point
29.670, -95.020
Record number
1321

What the Weather Service recorded

Tornado touchdown caused moderate damage to homes and apartments. Damage included in T.S. Frances summary.

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

The warnings

1 minute of warning. NWS HGX issued a tornado warning for this county at 09:31 UTC, 1 minute before the tornado touched down, in force until 10:35 UTC.

Issued (UTC)ExpiredProductOffice
06:29 UTC07:35 UTCTornado WarningHGX
07:03 UTC11:00 UTCFlash Flood WarningHGX
09:31 UTC10:35 UTCTornado WarningHGX
10:54 UTC14:50 UTCFlash Flood WarningHGX
11:18 UTC12:20 UTCTornado WarningHGX
13:58 UTC19:55 UTCFlash Flood 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 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.

Lake Charles Mun, LA (KLCH), 00:00Z

9.5 hours before the tornado, 182 km from the path. September 11, 1998.

Skew-T log-pSkew-T log-p diagram, Lake Charles Mun, LA at 00:00Z on 1998-09-11Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 26 joules per kilogram, CIN -67, lifted condensation level 452 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, Lake Charles Mun, LA at 00:00Z on 1998-09-11The 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 273 square meters per square second, 0 to 6 km bulk shear 17 knots.193958Sfc1 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
26 J/kg
Mixed-layer CIN
-67 J/kg
Surface CAPE
115 J/kg
Mixed-layer LCL
452 m above ground
0-6 km bulk shear
17 kt
0-1 km bulk shear
34 kt
0-1 km storm-relative helicity
273 m²/s²
0-3 km storm-relative helicity
445 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
4.5 K/km

Open this sounding in Storm Lab

Lake Charles Mun, LA (KLCH), 12:00Z

2.5 hours after it, 182 km from the path. September 11, 1998.

Skew-T log-pSkew-T log-p diagram, Lake Charles Mun, LA at 12:00Z on 1998-09-11Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 40 joules per kilogram, CIN -111, lifted condensation level 636 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, Lake Charles Mun, LA at 12:00Z on 1998-09-11The 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 295 square meters per square second, 0 to 6 km bulk shear 24 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
40 J/kg
Mixed-layer CIN
-111 J/kg
Surface CAPE
47 J/kg
Mixed-layer LCL
636 m above ground
0-6 km bulk shear
24 kt
0-1 km bulk shear
30 kt
0-1 km storm-relative helicity
295 m²/s²
0-3 km storm-relative helicity
422 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.3
0-3 km lapse rate
4.3 K/km

Open this sounding in Storm Lab

The radar

The Houston radar (KHGX), 23 km away, was scanning. The volume nearest the touchdown began at 09:29 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 1998 tornado in TexasEvery tornado in Texas since 1950Warnings in force in Texas nowThe forecast where you are

The other tornadoes of September 11, 1998

7 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
September 1110:55 AM CDTF1Jefferson Davis Parish, LA1.030$70,000
September 1112:56 PM PDTF0Clark, NV0.130$30,000
September 115:18 PM CDTF0Acadia Parish, LA2.0302$5.0 million
September 115:56 PM CDTF1Evangeline Parish, LA5.0303$2.0 million
September 116:15 PM CDTF0Allen Parish, LA1.030$10,000
September 1111:30 PM CDTF0Lafayette Parish, LA1.030$100,000
September 1112:00 AM CDTF0Saint Landry Parish, LA1.030$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.