Tornadoes · United States · Minnesota · 1997

F1 tornado, Camp Ripley Jct, Minnesota, September 18, 1997

This F1 tornado ran 1.5 miles across Morrison County on September 18, 1997, touching down at 5:25 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
September 18, 1997
Touchdown
5:25 PM CDT (22:25 UTC)
Path length
1.5 miles (2.4 km)
Path width
100 yards (91 m)
Deaths
0
Injuries
0
County
Morrison County
Touchdown point
46.070, -94.330
Lift-off point
46.080, -94.320
Record number
1047

The warnings

1 minute of warning. NWS MPX issued a tornado warning for this county at 22:24 UTC, 1 minute before the tornado touched down, in force until 23:15 UTC.

Issued (UTC)ExpiredProductOffice
22:13 UTC22:45 UTCSevere Thunderstorm WarningMPX
22:24 UTC23:15 UTCTornado WarningMPX
23:08 UTC00:00 UTCTornado WarningMPX
23:34 UTC00:15 UTCTornado WarningMPX
00:08 UTC00:45 UTCTornado WarningMPX
00:43 UTC01:30 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 Slight Risk. The outlook in force was issued at 05:58 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.

Minneapolis, MN (KMPX), 12:00Z

10.4 hours before the tornado, 147 km from the path. September 18, 1997.

Skew-T log-pSkew-T log-p diagram, Minneapolis, MN at 12:00Z on 1997-09-18Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 228 joules per kilogram, CIN -404, lifted condensation level 1391 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 1997-09-18The 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 477 square meters per square second, 0 to 6 km bulk shear 42 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
228 J/kg
Mixed-layer CIN
-404 J/kg
Surface CAPE
0 J/kg
Mixed-layer LCL
1391 m above ground
0-6 km bulk shear
42 kt
0-1 km bulk shear
44 kt
0-1 km storm-relative helicity
477 m²/s²
0-3 km storm-relative helicity
490 m²/s²
Significant tornado parameter
0.0
Supercell composite
1.3
0-3 km lapse rate
4.0 K/km

Open this sounding in Storm Lab

Minneapolis, MN (KMPX), 00:00Z

1.6 hours after it, 147 km from the path. September 19, 1997.

Skew-T log-pSkew-T log-p diagram, Minneapolis, MN at 00:00Z on 1997-09-19Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 1943 joules per kilogram, CIN -114, lifted condensation level 867 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 1997-09-19The 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 298 square meters per square second, 0 to 6 km bulk shear 63 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
1943 J/kg
Mixed-layer CIN
-114 J/kg
Surface CAPE
2702 J/kg
Mixed-layer LCL
867 m above ground
0-6 km bulk shear
63 kt
0-1 km bulk shear
31 kt
0-1 km storm-relative helicity
298 m²/s²
0-3 km storm-relative helicity
399 m²/s²
Significant tornado parameter
2.1
Supercell composite
8.4
0-3 km lapse rate
5.8 K/km

Open this sounding in Storm Lab

The surface observations

Little Falls (LXL), 14 km from the path, in the two hours either side.

Time (UTC)Temp (°F)Dew point (°F)WindGust (kt)Pressure (mb)Weather
20:35 UTC78.871.6130° 7 kt1000.3
20:55 UTC80.673.4120° 9 kt999.7
21:15 UTC80.671.6170° 10 kt999.7
21:35 UTC80.671.6170° 12 kt999.7
21:55 UTC80.673.4160° 9 kt999
22:15 UTC80.673.4150° 14 kt998TS
22:35 UTC80.673.4190° 15 kt998.3VCTS
22:55 UTC80.671.6190° 14 kt999
23:15 UTC78.871.6200° 10 kt999
23:35 UTC78.873.4180° 7 kt998.6
23:55 UTC7773.4180° 6 kt999VCTS
00:15 UTC73.473.410° 11 kt998.3TS

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

This ground now

The live radar over the trackEvery 1997 tornado in MinnesotaEvery tornado in Minnesota since 1950Warnings in force in Minnesota nowThe forecast where you are

The other tornadoes of September 18, 1997

6 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
September 189:15 AM PDTF0Tillamook, OR0.510
September 189:30 AM PDTF0Tillamook, OR0.510
September 186:15 PM CDTF3Morrison, MN17.080011$1.7 million
September 186:48 PM CDTF1Mille Lacs, MN2.0500
September 187:03 PM CDTF2Kanabec, MN17.0450
September 187:30 PM CDTF2Morrison, MN8.0300

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.