Tornadoes · United States · Minnesota · 2004

F0 tornado, Brown County, Minnesota, April 18, 2004

This F0 tornado ran 0.1 miles across Brown County on April 18, 2004, touching down at 5:35 PM CDT and reaching 15 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 18, 2004
Touchdown
5:35 PM CDT (22:35 UTC)
Path length
0.1 miles (0.2 km)
Path width
15 yards (14 m)
Deaths
0
Injuries
0
County
Brown County
Touchdown point
44.430, -94.830
Lift-off point
44.430, -94.830
Record number
851

The warnings

1 minute of warning. NWS MPX issued a tornado warning for this county at 22:34 UTC, 1 minute before the tornado touched down, in force until 23:00 UTC.

Issued (UTC)ExpiredProductOffice
22:18 UTC23:00 UTCSevere Thunderstorm WarningMPX
22:34 UTC23:00 UTCTornado WarningMPX
22:59 UTC00:00 UTCSevere Thunderstorm WarningMPX
23:02 UTC23:45 UTCTornado WarningMPX
23:45 UTC00:30 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, with a 0.05 chance of a tornado within 25 miles. The outlook in force was issued at 20:00 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

10.6 hours before the tornado, 108 km from the path. April 18, 2004.

Skew-T log-pSkew-T log-p diagram, Minneapolis, MN at 12:00Z on 2004-04-18Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 680 joules per kilogram, CIN -274, lifted condensation level 697 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 2004-04-18The 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 361 square meters per square second, 0 to 6 km bulk shear 61 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
680 J/kg
Mixed-layer CIN
-274 J/kg
Surface CAPE
0 J/kg
Mixed-layer LCL
697 m above ground
0-6 km bulk shear
61 kt
0-1 km bulk shear
38 kt
0-1 km storm-relative helicity
361 m²/s²
0-3 km storm-relative helicity
401 m²/s²
Significant tornado parameter
0.0
Supercell composite
4.3
0-3 km lapse rate
4.1 K/km

Open this sounding in Storm Lab

Minneapolis, MN (KMPX), 00:00Z

1.4 hours after it, 108 km from the path. April 19, 2004.

Skew-T log-pSkew-T log-p diagram, Minneapolis, MN at 00:00Z on 2004-04-19Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 671 joules per kilogram, CIN -31, lifted condensation level 2341 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 2004-04-19The 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 244 square meters per square second, 0 to 6 km bulk shear 39 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
671 J/kg
Mixed-layer CIN
-31 J/kg
Surface CAPE
648 J/kg
Mixed-layer LCL
2341 m above ground
0-6 km bulk shear
39 kt
0-1 km bulk shear
34 kt
0-1 km storm-relative helicity
244 m²/s²
0-3 km storm-relative helicity
328 m²/s²
Significant tornado parameter
0.0
Supercell composite
4.7
0-3 km lapse rate
8.6 K/km

Open this sounding in Storm Lab

What was reported nearby

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

Time (UTC)ReportWhereCountyRemark
22:27 UTCHAIL 0.88MorganRedwood, MN
22:30 UTCTORNADO6 N EvanBrown, MNMETEOROLOGIST SPOTTED SMALL TORNADO NORTH OF EVAN THAT LASTED ABOUT ONE MINUTE.
22:55 UTCTSTM WND DMGStewartMcleod, MNCORN BINS BLOWN OVER.
23:17 UTCTSTM WND GST 75StordenCottonwood, MN
23:17 UTCHAIL 1StordenCottonwood, MN
23:38 UTCFUNNEL CLOUD5 W SpringfieldBrown, MN
23:40 UTCTSTM WND DMGFairfaxRenville, MNFEW TREES DOWN.
23:55 UTCTSTM WND GST 63St JamesWatonwan, MN

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

This ground now

The live radar over the trackEvery 2004 tornado in MinnesotaEvery tornado in Minnesota since 1950Warnings in force in Minnesota nowThe forecast where you are

The other tornadoes of April 18, 2004

13 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
April 181:43 PM EDTF0Cayuga, NY1.075$100,000
April 184:52 PM CDTF0Turner, SD0.150
April 184:58 PM CDTF1Lyon, IA4.0100$50,000
April 185:05 PM CDTF0Union, SD4.0100$10,000
April 185:15 PM CDTF0Sioux, IA0.150
April 185:20 PM CDTF1Nobles, MN0.5100$500,000
April 185:25 PM CDTF0Pierce, NE0.540
April 185:25 PM CDTF0Burnett, WI1.030
April 185:30 PM CDTF0Burnett, WI3.030
April 185:40 PM CDTF0Pierce, NE6.050
April 186:03 PM CDTF0Redwood, MN1.550
April 186:29 PM CDTF1Redwood, MN7.050
April 188:02 PM CDTF0Woodbury, IA0.150

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.