Tornadoes · United States · Minnesota · 1999

F0 tornado, Waterville to Warsaw, Minnesota, August 9, 1999

From Waterville to Warsaw, this F0 tornado ran 0.8 miles across Rice and Le Sueur counties on August 9, 1999, touching down at 7:38 PM CDT. 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
August 9, 1999
Touchdown
7:38 PM CDT (00:38 UTC)
Path length
0.8 miles (1.3 km)
Path width
0 yards (0 m)
Deaths
0
Injuries
0
Counties
Rice and Le Sueur counties
Touchdown point
44.250, -93.520
Lift-off point
44.280, -93.520
Record number
835

What the Weather Service recorded

Multiple vortex tornado crossed open fields and continued into Rice County.

Multiple vortex tornado crossed open fields. Continuation of tornado from Le Sueur County.

Few trees down. Tornado continued into Rice County and Camp Omega.

Trees down in Camp Omega. Continuation of tornado from Le Sueur County.

Few trees felled. Tornado cut swath through bean field.

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

The warnings

31 minutes of warning. NWS MPX issued a tornado warning for this county at 00:07 UTC, 31 minutes before the tornado touched down, in force until 00:40 UTC.

Issued (UTC)ExpiredProductOffice
00:07 UTC00:40 UTCTornado WarningMPX
00:37 UTC01:15 UTCTornado WarningMPX

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 19:52 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.

Minneapolis, MN (KMPX), 00:00Z

0.6 hours before the tornado, 65 km from the path. August 10, 1999.

Skew-T log-pSkew-T log-p diagram, Minneapolis, MN at 00:00Z on 1999-08-10Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 1808 joules per kilogram, CIN -66, lifted condensation level 733 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, Minneapolis, MN at 00:00Z on 1999-08-10The 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 291 square meters per square second, 0 to 6 km bulk shear 46 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
1808 J/kg
Mixed-layer CIN
-66 J/kg
Surface CAPE
1085 J/kg
Mixed-layer LCL
733 m above ground
0-6 km bulk shear
46 kt
0-1 km bulk shear
33 kt
0-1 km storm-relative helicity
291 m²/s²
0-3 km storm-relative helicity
301 m²/s²
Significant tornado parameter
2.4
Supercell composite
13.0
0-3 km lapse rate
4.3 K/km

Open this sounding in Storm Lab

Minneapolis, MN (KMPX), 12:00Z

11.4 hours after it, 65 km from the path. August 10, 1999.

Skew-T log-pSkew-T log-p diagram, Minneapolis, MN at 12:00Z on 1999-08-10Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 1 joules per kilogram, CIN -113, lifted condensation level 1108 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, Minneapolis, MN at 12:00Z on 1999-08-10The 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 60 square meters per square second, 0 to 6 km bulk shear 38 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
1 J/kg
Mixed-layer CIN
-113 J/kg
Surface CAPE
0 J/kg
Mixed-layer LCL
1108 m above ground
0-6 km bulk shear
38 kt
0-1 km bulk shear
18 kt
0-1 km storm-relative helicity
60 m²/s²
0-3 km storm-relative helicity
102 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
3.9 K/km

Open this sounding in Storm Lab

This ground now

The live radar over the trackEvery 1999 tornado in MinnesotaEvery tornado in Minnesota since 1950Warnings in force in Minnesota nowThe forecast where you are

The other tornadoes of August 9, 1999

11 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
August 95:55 PM CDTF1Stearns, MN0.30
August 96:34 PM CDTF1Nicollet, MN0.80
August 96:37 PM CDTF1Le Sueur, MN9.050$610,000
August 97:08 PM CDTF0Goodhue, MN0.10
August 97:34 PM CDTF0Rice, MN2.50
August 97:46 PM CDTF0Rice, MN1.050
August 98:41 PM CDTF0Faribault, MN0.10
August 98:43 PM CDTF0Dodge, MN1.050
August 98:47 PM CDTF0Faribault, MN0.10
August 99:02 PM CDTF2Winnebago, IA11.540$150,000
August 910:01 PM CDTF0Cerro Gordo, IA0.10

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.