Tornadoes · United States · Missouri · 1999

F1 tornado, Mexico to Rush Hill, Missouri, April 8, 1999

From Mexico to Rush Hill, this F1 tornado ran 10.0 miles across Audrain County on April 8, 1999, touching down at 6:30 PM CDT and reaching 100 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
April 8, 1999
Touchdown
6:30 PM CDT (23:30 UTC)
Path length
10.0 miles (16.1 km)
Path width
100 yards (91 m)
Deaths
0
Injuries
0
County
Audrain County
Touchdown point
39.180, -91.930
Lift-off point
39.250, -91.730
Record number
340

What the Weather Service recorded

The supercell that spawned the Midway and Hinton tornadoes produced a third tornado in Audrain County. The tornado first caused damage just west of Mexico where 3 billboards and several trees were downed. Just to the northeast of Mexico, the tornado caused damage at an industrial complex. One factory lost part of its roof and several smaller sheet metal buildings were destroyed. Near Highways J and KK a barn was extensively damaged and 2 grain bins destroyed. The last observed damage was about 5 miles northeast of Mexico. One barn was destroyed, 2 equipment buildings destroyed, and 2 homes suffered minor roof damage.

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

The warnings

9 minutes of warning. NWS LSX issued a tornado warning for this county at 23:21 UTC, 9 minutes before the tornado touched down, in force until 00:10 UTC.

Issued (UTC)ExpiredProductOffice
23:21 UTC00:10 UTCTornado WarningLSX
00:20 UTC01:10 UTCTornado WarningLSX

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 High Risk. The outlook in force was issued at 19:58 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.

Davenport, (KDVN), 12:00Z

11.5 hours before the tornado, 290 km from the path. April 8, 1999.

Skew-T log-pSkew-T log-p diagram, Davenport, at 12:00Z on 1999-04-08Temperature 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 -69741, lifted condensation level 2467 meters above ground. Wind barbs in knots down the right edge.LCL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°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, Davenport, at 12:00Z on 1999-04-08The 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 6 square meters per square second, 0 to 6 km bulk shear 61 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
-69741 J/kg
Surface CAPE
0 J/kg
Mixed-layer LCL
2467 m above ground
0-6 km bulk shear
61 kt
0-1 km bulk shear
7 kt
0-1 km storm-relative helicity
6 m²/s²
0-3 km storm-relative helicity
115 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
2.4 K/km

Open this sounding in Storm Lab

Davenport, (KDVN), 00:00Z

0.5 hours after it, 290 km from the path. April 9, 1999.

Skew-T log-pSkew-T log-p diagram, Davenport, at 00:00Z on 1999-04-09Temperature 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 -86910, lifted condensation level 935 meters above ground. Wind barbs in knots down the right edge.LCL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°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, Davenport, at 00:00Z on 1999-04-09The 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 746 square meters per square second, 0 to 6 km bulk shear 58 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
-86910 J/kg
Surface CAPE
0 J/kg
Mixed-layer LCL
935 m above ground
0-6 km bulk shear
58 kt
0-1 km bulk shear
42 kt
0-1 km storm-relative helicity
746 m²/s²
0-3 km storm-relative helicity
1216 m²/s²
Significant tornado parameter
0.0
Supercell composite
3.3
0-3 km lapse rate
3.2 K/km

Open this sounding in Storm Lab

The surface observations

Columbia (COU), 56 km from the path, in the two hours either side.

Time (UTC)Temp (°F)Dew point (°F)WindGust (kt)Pressure (mb)Weather
21:54 UTC7363170° 17 kt28963.1
22:35 UTC170° 22 kt30
22:54 UTC7063210° 37 kt48963.8
23:01 UTC210° 21 kt45
23:11 UTC220° 20 kt27
23:54 UTC6854240° 16 kt27964.8
00:54 UTC6646240° 17 kt23964.8

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

The radar

The St Louis radar (KLSX), 115 km away, was scanning. The volume nearest the touchdown began at 23:29 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 1999 tornado in MissouriEvery tornado in Missouri since 1950Warnings in force in Missouri nowThe forecast where you are

The other tornadoes of April 8, 1999

46 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
April 811:00 AM CDTF1Hamilton, NE4.050$300,000
April 811:54 AM CDTF1Merrick, NE3.040$200,000
April 811:56 AM CDTF0Nance, NE1.010$10,000
April 812:22 PM CDTF0Boone, NE1.040$10,000
April 81:06 PM CDTF1Colfax, NE4.0150$540,000
April 81:07 PM CDTF1Saunders, NE1.5400$380,000
April 81:12 PM CDTF0Saunders, NE3.570$40,000
April 81:33 PM CDTF1Story, IA2.002$800,000
April 81:48 PM CDTF0Washington, NE0.130$10,000
April 82:08 PM CDTF0Fremont, IA0.040
April 82:18 PM CDTF0Pottawattamie, IA0.360
April 82:22 PM CDTF1Page, IA5.070$10,000
April 82:30 PM CDTF1Andrew, MO13.502$750,000
April 82:36 PM CDTF1Page, IA8.04401$100,000
April 82:38 PM CDTF1Montgomery, IA8.060$40,000
April 82:48 PM CDTF1Page, IA9.0100$20,000
April 82:54 PM CDTF0Montgomery, IA5.080$10,000
April 82:54 PM CDTF4Taylor, IA49.01,0003$2.7 million
April 83:48 PM CDTF4Union, IA56.01,2501$2.4 million
April 84:20 PM CDTF2Carroll, MO53.52802$1.9 million
April 84:20 PM CDTF1Livingston, MO7.00$250,000
April 85:00 PM CDTF0Polk, IA0.230$40,000
April 85:13 PM CDTF2Warren, IA32.00$120,000
April 85:18 PM CDTF3Lucas, IA39.005$1.4 million
April 85:25 PM CDTF2Macon, MO17.0270$1.0 million
April 85:30 PM CDTF1Cooper, MO4.00$750,000
April 85:55 PM CDTF2Boone, MO4.01205
April 86:05 PM CDTF2Lewis, MO16.01502$2.1 million
April 86:05 PM CDTF2Boone, MO10.0120
April 86:15 PM CDTF3Davis, IA16.0300$650,000
April 86:25 PM CDTF0Jefferson, IA0.110
April 86:25 PM CDTF0Jefferson, IA0.110
April 86:30 PM CDTF1Cole, MO12.0200
April 86:35 PM CDTF3Hancock, IL7.5200$15 million
April 87:36 PM EDTF0Barnwell, SC0.550$1,000
April 87:47 PM EDTF1Allendale, SC9.050$30,000
April 87:00 PM CDTF1Osage, MO8.0200$1.0 million
April 87:15 PM CDTF0Webster, MO0.10$20,000
April 87:34 PM CDTF2Pike, MO to IL27.3120$150,000
April 87:35 PM CDTF0Henderson, IL20.010
April 88:10 PM CDTF1Scott, IL4.0120$100,000
April 88:27 PM CDTF1Morgan, IL9.5200
April 88:45 PM CDTF1Morgan, IL9.333316$1.8 million
April 810:18 PM CDTF1Madison, IL1.001
April 810:35 PM CDTF1Piatt, IL3.510013$150,000
April 811:32 PM CDTF0Cumberland, IL0.30$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.