Tornadoes · United States · Minnesota · 2006

F0 tornado, Mountain Lake, Minnesota, August 1, 2006

This F0 tornado ran 0.1 miles across Cottonwood County on August 1, 2006, touching down at 6:54 PM 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 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 1, 2006
Touchdown
6:54 PM CDT (23:54 UTC)
Path length
0.1 miles (0.2 km)
Path width
50 yards (46 m)
Deaths
0
Injuries
0
County
Cottonwood County
Touchdown point
43.900, -94.880
Lift-off point
43.900, -94.880
Record number
780

What the Weather Service recorded

A brief tornado caused no reported damage.

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

The warnings

No tornado warning for this county appears in the archive as in force at the moment the tornado touched down. One was issued for the county at another hour that day.

The county was under a severe thunderstorm watch, issued at 22:00 UTC and running to 05:00 UTC.

Issued (UTC)ExpiredProductOffice
20:24 UTC08:00 UTCFlash Flood WatchFSD
22:00 UTC05:00 UTCSevere Thunderstorm WatchFSD
23:52 UTC00:15 UTCSevere Thunderstorm WarningFSD
00:28 UTC00:44 UTCTornado WarningFSD

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 General Thunderstorms Risk. The outlook in force was issued at 19:28 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), 12:00Z

11.9 hours before the tornado, 147 km from the path. August 1, 2006.

Skew-T log-pSkew-T log-p diagram, Minneapolis, MN at 12:00Z on 2006-08-01Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 799 joules per kilogram, CIN -65, lifted condensation level 665 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 2006-08-01The 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 51 square meters per square second, 0 to 6 km bulk shear 15 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
799 J/kg
Mixed-layer CIN
-65 J/kg
Surface CAPE
349 J/kg
Mixed-layer LCL
665 m above ground
0-6 km bulk shear
15 kt
0-1 km bulk shear
15 kt
0-1 km storm-relative helicity
51 m²/s²
0-3 km storm-relative helicity
53 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
4.6 K/km

Open this sounding in Storm Lab

Minneapolis, MN (KMPX), 00:00Z

0.1 hours after it, 147 km from the path. August 2, 2006.

Skew-T log-pSkew-T log-p diagram, Minneapolis, MN at 00:00Z on 2006-08-02Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 778 joules per kilogram, CIN 0, lifted condensation level 476 meters above ground. Wind barbs in knots down the right edge.LCLEL10008507005003002001001 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 2006-08-02The 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 215 square meters per square second, 0 to 6 km bulk shear 38 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
778 J/kg
Mixed-layer CIN
0 J/kg
Surface CAPE
1230 J/kg
Mixed-layer LCL
476 m above ground
0-6 km bulk shear
38 kt
0-1 km bulk shear
27 kt
0-1 km storm-relative helicity
215 m²/s²
0-3 km storm-relative helicity
479 m²/s²
Significant tornado parameter
1.1
Supercell composite
7.9
0-3 km lapse rate
5.4 K/km

Open this sounding in Storm Lab

The radar

The Minneapolis radar (KMPX), 148 km away, was scanning. The volume nearest the touchdown began at 23:51 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.

What was reported nearby

Local storm reports within 60 km of the path, in the three hours either side.

Time (UTC)ReportWhereCountyRemark
23:54 UTCTORNADO3 Se Mountain LakeCottonwood, MNBRIEF TOUCHDOWN OF F0 TORNADO
00:19 UTCTORNADO2 Sw ButterfieldWatonwan, MNIN PROGRESS AT 719 PM SOUTHWEST OF BUTTERFIELD. TORNADO ROPED OUT AT 722 PM. TORNADO HAD DEBRIS FIELD AS IT DISSIPATED. CHASER NOTED ANOTHER TORNADO APPEARED IMMINENT TO DEVELOP.
00:19 UTCTORNADO3 S ButterfieldWatonwan, MNIN PROGRESS...BETWEEN BUTTERFIELD AND ODIN.
00:35 UTCTSTM WND GST 706 Ese Round LakeJackson, MNLARGE TREE DOWN IN YARD
00:43 UTCTORNADO3 S ButterfieldWatonwan, MNSTRUCTURAL DAMAGE REPORTED AT FARM HOUSE. CALLED IN AT 743 PM. UNKNOWN IF IT WAS THE SAME TORNADO AS PREVIOUSLY REPORTED. NO INJURIES.
00:44 UTCTORNADO1 N South BranchWatonwan, MNNEW TORNADO ON GROUND WITH DEBRIS NEAR COUNTY ROADS 27 AND 10. APPEARS TO BE MOVING EAST-SOUTHEAST.
00:47 UTCFUNNEL CLOUD1 N OdinWatonwan, MNFUNNEL APPEARS LIKE IT WILL SOON REACH THE GROUND.
00:48 UTCTORNADO4 S St JamesWatonwan, MNSTRUCTURAL DAMAGE REPORTED AT FARM HOUSE. UNCERTAIN IF THIS WAS THE SAME TORNADO AS PREVIOUSLY REPORTED. DAMAGE CALLED IN AT 748 PM. NO INJURIES.
01:00 UTCTSTM WND GST 85JacksonJackson, MN8 INCH DIAMETER TREES DOWN
01:00 UTCTSTM WND GST 85JacksonJackson, MN
01:05 UTCTSTM WND DMGDunnellMartin, MNTREES DOWN. CORN FLATTENED.
01:35 UTCTSTM WND DMGFairmontMartin, MNTREE DOWN. KSUM ON WEST SIDE OF TOWN MEASURED 54 MPH. PONDING OF WATER IN SOME INTERSECTIONS.

From the Iowa Environmental Mesonet's archive of National Weather Service local storm reports.

This ground now

The live radar over the trackEvery 2006 tornado in MinnesotaEvery tornado in Minnesota since 1950Warnings in force in Minnesota nowThe forecast where you are

The other tornadoes of August 1, 2006

3 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
August 17:14 PM CDTF3Watonwan, MN1.5440$2.0 million
August 17:33 PM CDTF1Watonwan, MN3.0100$500,000
August 17:44 PM CDTF1Watonwan, MN1.050$500,000

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.