Tornadoes · United States · Oregon · 1997

F0 tornado, Keizer, Oregon, May 31, 1997

This F0 tornado ran 1.5 miles across Marion County on May 31, 1997, touching down at 11:10 AM PDT and reaching 50 yards wide. It killed nobody, and did $10,000 of property damage.

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
May 31, 1997
Touchdown
11:10 AM PDT (18:10 UTC)
Path length
1.5 miles (2.4 km)
Path width
50 yards (46 m)
Deaths
0
Injuries
0
Property damage
$10,000
County
Marion County
Touchdown point
44.980, -123.020
Lift-off point
44.980, -122.980
Record number
374

What the Weather Service recorded

A tornado touched down near Chemawa Road and Highway 99 near Keizer at 1010 AM. Several people reported seeing the tornado on the ground for about 2 minutes. Three 30-40 foot tall trees were uprooted and a barn was damaged.

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.

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 05:57 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.

Salem/Mcnary, OR (KSLE), 12:00Z

6.2 hours before the tornado, 7 km from the path. May 31, 1997.

Skew-T log-pSkew-T log-p diagram, Salem/Mcnary, OR at 12:00Z on 1997-05-31Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 295 joules per kilogram, CIN -9, lifted condensation level 635 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, Salem/Mcnary, OR at 12:00Z on 1997-05-31The 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 65 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
295 J/kg
Mixed-layer CIN
-9 J/kg
Surface CAPE
171 J/kg
Mixed-layer LCL
635 m above ground
0-6 km bulk shear
61 kt
0-1 km bulk shear
20 kt
0-1 km storm-relative helicity
65 m²/s²
0-3 km storm-relative helicity
126 m²/s²
Significant tornado parameter
0.2
Supercell composite
0.9
0-3 km lapse rate
5.7 K/km

Open this sounding in Storm Lab

Salem/Mcnary, OR (KSLE), 00:00Z

5.8 hours after it, 7 km from the path. June 1, 1997.

Skew-T log-pSkew-T log-p diagram, Salem/Mcnary, OR at 00:00Z on 1997-06-01Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 170 joules per kilogram, CIN -2, lifted condensation level 773 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, Salem/Mcnary, OR at 00:00Z on 1997-06-01The 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 -27 square meters per square second, 0 to 6 km bulk shear 31 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
170 J/kg
Mixed-layer CIN
-2 J/kg
Surface CAPE
439 J/kg
Mixed-layer LCL
773 m above ground
0-6 km bulk shear
31 kt
0-1 km bulk shear
9 kt
0-1 km storm-relative helicity
-27 m²/s²
0-3 km storm-relative helicity
27 m²/s²
Significant tornado parameter
-0.0
Supercell composite
-0.1
0-3 km lapse rate
6.9 K/km

Open this sounding in Storm Lab

The surface observations

Salem/Mcnary (SLE), 8 km from the path, in the two hours either side.

Time (UTC)Temp (°F)Dew point (°F)WindGust (kt)Pressure (mb)Weather
16:20 UTC64.462.6180° 15 kt211011.5+RA BR
16:32 UTC62.660.8210° 10 kt1011.5+RA BR
16:56 UTC6260180° 3 kt1011.5-RA
17:05 UTC62.660.8240° 10 kt1011.9RA BR
17:17 UTC60.859220° 7 kt1011.9+RA BR
17:38 UTC60.859240° 4 kt1011.9+RA BR
17:48 UTC60.859240° 7 kt1012.2RA BR
17:56 UTC6160240° 5 kt1012.2+RA BR
18:03 UTC60.859290° 3 kt1012.2+RA BR
18:16 UTC60.859360° 5 kt1012.2RA BR
18:23 UTC60.859320° 6 kt1012.2RA BR
18:30 UTC5959300° 5 kt1012.2RA BR
18:56 UTC60590° 0 kt1012.9-RA BR
19:13 UTC60.859180° 4 kt1013.5RA
19:56 UTC6359180° 9 kt1013.9

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

The radar

The Portland,OR radar (KRTX), 82 km away, was scanning. The volume nearest the touchdown began at 18:10 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 1997 tornado in OregonEvery tornado in Oregon since 1950Warnings in force in Oregon nowThe forecast where you are

The other tornadoes of May 31, 1997

10 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
May 312:40 AM CDTF0Kimble, TX0.113
May 3112:40 PM PDTF1Lincoln, WA12.050$300,000
May 311:45 PM PDTF1Spokane, WA5.050$350,000
May 312:05 PM PDTF2Kootenai, ID5.050$50,000
May 312:10 PM PDTF0Nez Perce, ID0.123
May 315:30 PM EDTF0Broward, FL0.123
May 313:15 PM PDTF1Pierce, WA0.510$150,000
May 314:55 PM MDTF0Bannock, ID0.120
May 315:05 PM MDTF1Jefferson, ID4.0200
May 315:45 PM PDTF0Clark, WA0.520$10,000

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.