Tornadoes · United States · Minnesota · 2004

F0 tornado, Glyndon to Rollag, Minnesota, July 12, 2004

Name: F0 tornado, Glyndon to Rollag, Minnesota, July 12, 2004
Start: 2004-07-13T03:32:00.000Z
Location: Glyndon to Rollag, Minnesota

From Glyndon to Rollag, this F0 tornado ran 0.5 miles across Clay County on July 12, 2004, touching down at 10:32 PM CDT and reaching 25 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.

F040 to 72 mphthis tornado
Light damage. Surface peeled off some roofs, gutters and siding damaged, branches broken, shallow-rooted trees pushed over.
F173 to 112 mph
Moderate damage. Roofs badly stripped, mobile homes overturned or badly damaged, exterior doors lost, windows broken.
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.
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.
F4207 to 260 mph
Devastating damage. Well-built houses leveled, structures with weak foundations moved some distance, cars thrown and large missiles generated.
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.
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: July 12, 2004
Touchdown: 10:32 PM CDT (03:32 UTC)
Path length: 0.5 miles (0.8 km)
Path width: 25 yards (23 m)
Deaths: 0
Injuries: 0
County: Clay County
Touchdown point: 46.900, -96.580
Lift-off point: 46.900, -96.580
Record number: 1435

What the Weather Service recorded

A tornado briefly tracked through a wheat field.

Several buildings were damaged at the Western Minnesota Steam Threshers Reunion grounds near Rollag. Some antique farm machinery inside the buildings was also damaged.

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

The forecast that day

The Storm Prediction Center had this point in a Slight Risk. The outlook in force was issued at 02:10 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.

What forecasters said that day

The local office's own words before the tornado touched down, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Grand Forks, ND wrote its last area forecast discussion before the tornado touched down at Jul 12, 8:40 PM CDT, 1 hour 52 minutes earlier.

Area forecast discussion, Jul 12, 8:40 PM CDT, 1 hour 52 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EASTERN ND/GRAND FORKS ND
840 PM CDT MON JUL 12 2004

.UPDATED DISCUSSION...

UPDATED ONCE MORE...BASED ON RADAR AND NEW SWODY1...ADDED ISOLATED
THUNDERSTORMS TO MUCH OF MN CWA AS WELL AND MENTIONED PSBL SEVERE
DUE TO CURRENT STORM STRENGTH NEAR JAMESTOWN.
------------------------------------------------------------
.PREVIOUS DISCUSSION...

UPDATED FCST TO MENTION ISOLATED THUNDERSTORMS IN SE ND UNTIL
MIDNIGHT.  WESTERLY SFC FLOW OVER ENTIRE FCST AREA...BUT BEEN
WATCHING WELL DEFINED DEW PT BOUNDARY OVER SE HALF OF NORTH DAKOTA
THIS EVENING.  50 DEW PTS AT DVL/BIS TO 65-70 AT FAR-JMS TO LOWER
70S IN NE SD. 01Z OBS EVEN SHOWING SOME BACKING OF THE WINDS MORE
TOWARD TTHE SOUTH AT SISSETON AND WHEATON WITH DEW PTS CLIMBING TO
THE LOWER 70S.  SO ENOUGH HEATING AND MOISTURE FOR ISOLD THUNDER
THIS EVENING. CAPES NR 4000 J/KG  WILL HAVE TO SEE HOW MUCH
DEVELOPMENT OCCURS...BUT POTENTIAL IS THERE FOR A FEW HOURS OF
STRONG OR SEVERE...SOME STRONG.  FREEZING LEVELS AROUND 12500 FT
AGL...LOWER THAN LAST NIGHT.

ALSO SCT STORMS IN MANITOBA CLOSER TO ANOTHER DEW POINT FRONT MOVING
SOUTH AND EAST AROUND CANADIAN UPPER LOW.  ONE SUPERCELL MOVING
TOWARD NORTHWEST ANGLE MN HAS WEAKENED A BIT.

&&

.FGF WATCHES/WARNINGS/ADVISORIES...

ND...NONE.
MN...NONE.

&&

RIDDLE

Hazardous weather outlook, Jul 12, 8:30 PM CDT, 2 hours 2 minutes before

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE EASTERN ND/GRAND FORKS
830 PM CDT MON JUL 12 2004

MNZ001>009-013>017-022>024-027>032-040-NDZ006>008-014>016-024-
026>030-038-039-049-052>054-130400-
BARNES-BENSON-CASS-CAVALIER-CLAY-EAST BECKER-EAST MARSHALL-
EAST OTTER TAIL-EAST POLK-EASTERN WALSH COUNTY-EDDY-GRAND FORKS-
GRANT-GRIGGS-HUBBARD-KITTSON-LAKE OF THE WOODS-MAHNOMEN-NELSON-
NORMAN-NORTH BELTRAMI-NORTH CLEARWATER-PEMBINA-PENNINGTON-RAMSEY-
RANSOM-RED LAKE-RICHLAND-ROSEAU-SARGENT-SOUTH BELTRAMI-
SOUTH CLEARWATER-STEELE-TOWNER-TRAILL-WADENA-WEST BECKER-
WEST MARSHALL-WEST OTTER TAIL-WEST POLK-WESTERN WALSH COUNTY-WILKIN-
830 PM CDT MON JUL 12 2004

...SEVERE THUNDERSTORMS POSSIBLE OVER SOUTHEAST NORTH DAKOTA AND
WEST CENTRAL MINNESOTA UNTIL MIDNIGHT...

THIS HAZARDOUS WEATHER OUTLOOK IS FOR EASTERN NORTH DAKOTA...WEST
CENTRAL AND NORTHWEST MINNESOTA.

.DAY ONE...TONIGHT
ISOLATED TO SCATTERED SEVERE THUNDERSTORMS ARE POSSIBLE OVER
SOUTHEAST NORTH DAKOTA AND WEST CENTRAL MINNESOTA UNTIL
MIDNIGHT...MAINLY EAST OF A ROSEAU TO MAYVILLE TO JAMESTOWN LINE.
LARGE HAIL AND DAMAGING WINDS ARE POSSIBLE. AN UPPER LEVEL LOW OVER
CANADA WILL MOVE EAST THIS EVENING.  JET ENERGY ON THE SOUTHERN SIDE
OF THE SYSTEM WILL CAUSE UPWARD MOTION OVER THE REGION.  A DEW POINT
FRONT SEPARATING 50 DEW PTS AT DEVILS LAKE AND BISMARCK TO AROUND 70
IN FARGO AND FERGUS FALLS WILL BE THE TRIGGER FOR THE STORMS TO FORM.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

THERE IS A CHANCE OF THUNDERSTORMS FOR NORTHWEST MINNESOTA STARTING
WEDNESDAY NIGHT AND THEN SPREADING INTO EASTERN NORTH DAKOTA BY
FRIDAY NIGHT.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE REQUIRED THIS EVENING.

FOR ADDITIONAL WEATHER INFORMATION, CHECK OUR WEB SITE AT
HTTP://WWW.CRH.NOAA.GOV/FGF/INDEX.HTML (ALL LOWER CASE)

RIDDLE

In the hours before

Local storm report, Jul 12, 10:08 PM CDT, 24 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE EASTERN ND/GRAND FORKS
1008 PM CDT MON JUL 12 2004

..TIME...   ...EVENT...     ...CITY LOCATION...      ...LAT.LON...
..DATE...   ....MAG....     ..COUNTY LOCATION...ST.. ...SOURCE....
            ..REMARKS..

1000 PM     HAIL             3 W HARWOOD             46.98N 96.94W
07/12/2004  1.75 INCH        CASS               ND   TRAINED SPOTTER

1005 PM     HAIL             1 N HARWOOD             46.99N 96.88W
07/12/2004  1.75 INCH        CASS               ND   TRAINED SPOTTER

1007 PM     HAIL             1 E HARWOOD             46.98N 96.86W
07/12/2004  1.75 INCH        CASS               ND   TRAINED SPOTTER

&&

DTR

Local storm report, Jul 12, 10:20 PM CDT, 12 minutes before

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Local storm report, Jul 12, 10:22 PM CDT, 10 minutes before

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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

3.5 hours before the tornado, 263 km from the path. July 13, 2004.

Skew-T log-p

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.

Hodograph

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: 1108 J/kg
Mixed-layer CIN: -111 J/kg
Surface CAPE: 4032 J/kg
Mixed-layer LCL: 1722 m above ground
0-6 km bulk shear: 45 kt
0-1 km bulk shear: 10 kt
0-1 km storm-relative helicity: 19 m²/s²
0-3 km storm-relative helicity: 60 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 2.7
0-3 km lapse rate: 6.6 K/km

Open this sounding in Storm Lab

The surface observations

Moorhead Municipal (JKJ), 9 km from the path, in the two hours either side.

Time (UTC)	Temp (°F)	Dew point (°F)	Wind	Gust (kt)	Pressure (mb)	Weather
00:00 UTC

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

The radar

The Fargo/Grand Forks radar (KMVX), 90 km away, was scanning. The volume nearest the touchdown began at 03:33 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 track Every 2004 tornado in Minnesota Every tornado in Minnesota since 1950 Warnings in force in Minnesota now The forecast where you are

The other tornadoes of July 12, 2004

13 more were confirmed in the United States that day.

Date	Time	Rating	Where	Path (mi)	Width (yd)	Injuries	Damage
July 12	1:28 PM EDT	F1	Cecil, MD	0.5	100
July 12	1:30 PM EDT	F1	Cecil, MD	0.8	200
July 12	4:10 PM EDT	F0	Kent, DE	0.5	100
July 12	7:10 PM CDT	F2	Wheeler, NE	1.5	40		$130,000
July 12	7:30 PM CDT	F1	Wheeler, NE	1.5	20	2	$170,000
July 12	7:35 PM CDT	F2	Wheeler, NE	1.0	40		$90,000
July 12	7:39 PM CDT	F0	Garfield, NE	1.0	20		$1,000
July 12	8:59 PM CDT	F0	Howard, NE	0.1	25		$70,000
July 12	10:52 PM CDT	F1	Clay, MN	10.0	50		$100,000
July 12	11:13 PM CDT	F0	Becker, MN	0.5	25
July 12	11:15 PM CDT	F1	Otter Tail, MN	5.0	50		$400,000
July 12	11:30 PM CDT	F1	Otter Tail, MN	14.0	50		$600,000
July 12	12:05 AM CDT	F0	Otter Tail, MN	0.5	25

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.