Tornadoes · United States · North Dakota · 2005

F1 tornado, Horace, North Dakota, September 5, 2005

This F1 tornado ran 1.5 miles across Cass County on September 5, 2005, touching down at 8:00 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 5, 2005
Touchdown
8:00 PM CDT (01:00 UTC)
Path length
1.5 miles (2.4 km)
Path width
100 yards (91 m)
Deaths
0
Injuries
0
County
Cass County
Touchdown point
46.750, -96.820
Lift-off point
46.750, -96.780
Record number
1166

What the Weather Service recorded

After strong winds and heavy rain hit a farmstead, a tornado followed closely behind. The tornado tracked intermittently along a 4 mile path. A 30 foot concrete silo was lifted and blown onto a machine shed. Concrete pieces spread in a 60 degree arc 40 to 50 feet from the foundation. One-half of the machine shed was demolished by silo debris. Numerous trees were also snapped off. A window was blown in and siding was ripped off the house. The peak wind speeds were estimated at 120 mph.

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.

Issued (UTC)ExpiredProductOffice
09:21 UTC09:45 UTCSevere Thunderstorm WarningFGF
20:45 UTC05:00 UTCSevere Thunderstorm WarningWNS
00:11 UTC00:56 UTCTornado WarningFGF

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, with a 0.02 chance of a tornado within 25 miles. The outlook in force was issued at 00:59 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.

Aberdeen, SD (KABR), 00:00Z

1.0 hours before the tornado, 240 km from the path. September 6, 2005.

Skew-T log-pSkew-T log-p diagram, Aberdeen, SD at 00:00Z on 2005-09-06Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 239 joules per kilogram, CIN -42, lifted condensation level 1970 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, Aberdeen, SD at 00:00Z on 2005-09-06The 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 -24 square meters per square second, 0 to 6 km bulk shear 30 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
239 J/kg
Mixed-layer CIN
-42 J/kg
Surface CAPE
262 J/kg
Mixed-layer LCL
1970 m above ground
0-6 km bulk shear
30 kt
0-1 km bulk shear
21 kt
0-1 km storm-relative helicity
-24 m²/s²
0-3 km storm-relative helicity
-14 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
6.8 K/km

Open this sounding in Storm Lab

Aberdeen, SD (KABR), 12:00Z

11.0 hours after it, 240 km from the path. September 6, 2005.

Skew-T log-pSkew-T log-p diagram, Aberdeen, SD at 12:00Z on 2005-09-06Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 0 joules per kilogram, CIN -67162, lifted condensation level 1291 meters above ground. Wind barbs in knots down the right edge.LCL10008507005003002001001 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, Aberdeen, SD at 12:00Z on 2005-09-06The 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 1 square meters per square second, 0 to 6 km bulk shear 37 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
0 J/kg
Mixed-layer CIN
-67162 J/kg
Surface CAPE
0 J/kg
Mixed-layer LCL
1291 m above ground
0-6 km bulk shear
37 kt
0-1 km bulk shear
5 kt
0-1 km storm-relative helicity
1 m²/s²
0-3 km storm-relative helicity
38 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
4.1 K/km

Open this sounding in Storm Lab

The radar

The Fargo/Grand Forks radar (KMVX), 95 km away, was scanning. The volume nearest the touchdown began at 01:00 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
00:10 UTCHAIL 13 Nnw EmbdenCass, ND
00:15 UTCHAIL 0.881 S CasseltonCass, NDPENNY TO NICKEL SIZED HAIL THROUGH 718 PM AT I-94 AND HWY 18 INTERSECTION.
00:30 UTCFUNNEL CLOUDWest FargoCass, ND
00:30 UTCTSTM WND DMG3 S MapletonCass, NDABOUT 5 INCH DIAMETER TREE SNAPPED OFF.
00:35 UTCFUNNEL CLOUD2 Sw West FargoCass, NDFUNNEL SIGHTED OFF WEST END OF EAGLE RUN SUBDIVISION.
00:40 UTCTSTM WND DMGFargoCass, ND40 BY 160 FOOT TENT FELLED BY THUNDERSTORM WINDS. 4 INCH POSTS WERE SHEARED. CONCESSION STAND DEMOLISHED.
00:43 UTCTSTM WND GST 804 S HoraceCass, NDTREES UPROOTED AND ANTENAE BLOWN OFF HOUSE ROOF.
00:45 UTCTSTM WND DMG4 Sse HoraceCass, NDNUMEROUS BRANCHES BROKEN OFF. LARGE STEEL GRAIN BIN DENTED IN. MOBILE HOME PARKED PARALLEL TO WIND WAS LIFTED SLIGHTLY AND ROCKED QUITE VIOLENTLY.
00:45 UTCTSTM WND DMGFargoCass, ND40 BY 160 FOOT TENT FELLED BY THUNDERSTORM WINDS. 4 INCH POSTS WERE SHEARED.
00:45 UTCTORNADO6 Sse HoraceCass, ND30 FOOT CONCRETE SILO LIFTED ONTO MACHINE SHED, WINDOWS BLOWN OUT AND SIDING RIPPED FROM HOUSE
00:48 UTCTSTM WND DMG4 Se HoraceCass, NDNUMEROUS TREES BROKEN DOWN ALONG WILD RICE RIVER.
00:50 UTCTSTM WND GST 654 E LeonardCass, NDLARGE BRANCHES BLOWN DOWN.
00:50 UTCTORNADO 24 Sse HoraceCass, NDTORNADO FOLLOWED CLOSELY AFTER STRONG WINDS AND HEAVY RAIN HIT THE FARMSTED. TORNADO TRACKED INTERMITTENTLY FOR ABOUT 4 MILES TO 2 NORTH OF HICKSON BY 802 PM. 30 FOOT CONCRETE SILO LIFTED AND BLOWN ONTO MACHINE SHED. CON
00:55 UTCTSTM WND DMGHicksonCass, NDEVERGREEN TREES TIPPED OR UPROOTED.
01:00 UTCTORNADO 11 W Wild RiceCass, NDTORNADO TRACKED FROM NEAR THE WILD RICE RIVER FOR ABOUT ONE AND ONE-HALF MILES TO THE RED RIVER ABOUT 1 ENE WILD RICE BY 804 PM. TORNADO CONTINUED INTO CLAY COUNTY OF MINNESOTA ABOUT 2 NW RUSTAD. SIGNAGE AND FENCING WERE
01:10 UTCHAIL 0.752 S AbercrombieRichland, ND

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

This ground now

The live radar over the trackEvery 2005 tornado in North DakotaEvery tornado in North Dakota since 1950Warnings in force in North Dakota nowThe forecast where you are

The other tornadoes of September 5, 2005

3 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
September 57:50 PM CDTF2Cass, ND4.0200
September 58:04 PM CDTF1Clay, MN2.5100
September 57:26 PM MDTF0Wallace, KS1.025

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.