Tornadoes · United States · North Dakota · 2006

F2 tornado, Underwood, North Dakota, August 24, 2006

Name: F2 tornado, Underwood, North Dakota, August 24, 2006
Start: 2006-08-24T18:55:00.000Z
Location: Underwood, North Dakota

This F2 tornado ran 2.0 miles across McLean County on August 24, 2006, touching down at 1:55 PM CDT and reaching 90 yards wide. It killed nobody, and did $200,000 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.

F040 to 72 mph
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 mphthis tornado
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: F2
Date: August 24, 2006
Touchdown: 1:55 PM CDT (18:55 UTC)
Path length: 2.0 miles (3.2 km)
Path width: 90 yards (82 m)
Deaths: 0
Injuries: 0
Property damage: $200,000
County: McLean County
Touchdown point: 47.350, -101.300
Lift-off point: 47.370, -101.270
Record number: 823

What the Weather Service recorded

This low end F2 tornado, on the order of 120 mph, produced considerable damage to a farm house and outbuildings 9 miles southwest of Underwood. The attached garage was completely torn from the two story house, and the roofing materials were also torn away, leaving the trusses visible. One detached shop, garden shed, and well house were destroyed. Items from the property were found 1/2 mile away. Nearby power lines were down. National Weather Service personnel conducted storm surveys of the area on two different days.

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

The warnings

15 minutes of warning. NWS BIS issued a tornado warning for this county at 18:40 UTC, 15 minutes before the tornado touched down, in force until 19:15 UTC.

The county was under a severe thunderstorm watch, issued at 16:52 UTC and running to 20:40 UTC.

Issued (UTC)	Expired	Product	Office
09:42 UTC	16:52 UTC	Severe Thunderstorm Watch	BIS
12:31 UTC	13:30 UTC	Severe Thunderstorm Warning	BIS
13:27 UTC	14:30 UTC	Severe Thunderstorm Warning	BIS
14:00 UTC	21:00 UTC	Flash Flood Watch	BIS
14:31 UTC	15:30 UTC	Severe Thunderstorm Warning	BIS
15:13 UTC	16:00 UTC	Tornado Warning	BIS
16:00 UTC	16:45 UTC	Severe Thunderstorm Warning	BIS
16:52 UTC	20:40 UTC	Severe Thunderstorm Watch	BIS
17:13 UTC	18:15 UTC	Severe Thunderstorm Warning	BIS
18:01 UTC	18:45 UTC	Severe Thunderstorm Warning	BIS
18:40 UTC	19:15 UTC	Tornado Warning	BIS
18:48 UTC	19:45 UTC	Severe Thunderstorm Warning	BIS
19:13 UTC	19:45 UTC	Tornado Warning	BIS
19:17 UTC	20:15 UTC	Severe Thunderstorm Warning	BIS
19:46 UTC	20:15 UTC	Tornado Warning	BIS

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 16:33 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 Bismarck, ND wrote its last area forecast discussion before the tornado touched down at Aug 24, 9:08 AM CDT, 4 hours 47 minutes earlier.

Area forecast discussion, Aug 24, 9:08 AM CDT, 4 hours 47 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
908 AM CDT THU AUG 24 2006

.UPDATE...
BASED ON A QUICK LOOK AT QPF PROGS AND CURRENT RADAR TRENDS HAVE
POSTED A FLASH FLOOD WATCH FOR TODAY IN THE NORTHWEST AND CENTRAL.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH UNTIL 4 PM CDT /3 PM MDT/ THIS AFTERNOON FOR
NDZ001-NDZ002-NDZ003-NDZ004-NDZ005-NDZ009-NDZ010-NDZ011-NDZ012-
NDZ013-NDZ017-NDZ018-NDZ019-NDZ020-NDZ021-NDZ022-NDZ023-NDZ025-
NDZ034-NDZ035-NDZ036-NDZ037-NDZ047-NDZ048-NDZ050-NDZ051.

&&

LEBLANG

Hazardous weather outlook, Aug 24, 4:22 AM CDT, 9 hours 33 minutes before

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE BISMARCK ND
422 AM CDT THU AUG 24 2006

NDZ001>005-009>013-017>023-025-031>037-040>048-050-051-250930-
DIVIDE-BURKE-RENVILLE-BOTTINEAU-ROLETTE-WILLIAMS-MOUNTRAIL-WARD-
MCHENRY-PIERCE-MCKENZIE-DUNN-MERCER-OLIVER-MCLEAN-SHERIDAN-WELLS-
FOSTER-GOLDEN VALLEY-BILLINGS-STARK-MORTON-BURLEIGH-KIDDER-
STUTSMAN-SLOPE-HETTINGER-GRANT-BOWMAN-ADAMS-SIOUX-EMMONS-LOGAN-
LA MOURE-MCINTOSH-DICKEY-
422 AM CDT THU AUG 24 2006 /322 AM MDT THU AUG 24 2006/

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTH CENTRAL
NORTH DAKOTA...NORTHWEST NORTH DAKOTA...SOUTH CENTRAL NORTH
DAKOTA...SOUTHEAST NORTH DAKOTA AND SOUTHWEST NORTH DAKOTA.

.DAY ONE...TODAY AND TONIGHT

THUNDERSTORMS WILL SPREAD FROM WESTERN INTO CENTRAL NORTH DAKOTA
TODAY...THEN END FROM THE WEST TONIGHT. SOME OF THE THUNDERSTORMS
COULD BE SEVERE WITH HEAVY RAIN.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED TODAY AND EARLY TONIGHT.

In the hours before

Local storm report, Aug 24, 12:52 PM CDT, 1 hour 3 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BISMARCK ND
1252 PM CDT THU AUG 24 2006

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

1235 PM     HAIL             RICHARDTON              46.88N 102.32W
08/24/2006  E0.75 INCH       STARK              ND   TRAINED SPOTTER

            SOME PEA SIZE HAIL AS WELL.

&&

VJENSEN

Local storm report, Aug 24, 1:14 PM CDT, 41 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BISMARCK ND
114 PM CDT THU AUG 24 2006

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

1252 PM     HAIL             1 SE LINCOLN            46.75N 100.69W
08/24/2006  E0.75 INCH       BURLEIGH           ND   TRAINED SPOTTER

            MOSTLY PEA SIZE HAIL

&&

VJENSEN

Local storm report, Aug 24, 1:16 PM CDT, 39 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BISMARCK ND
116 PM CDT THU AUG 24 2006

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

0105 PM     HAIL             LINCOLN                 46.77N 100.70W
08/24/2006  E0.88 INCH       BURLEIGH           ND   NWS EMPLOYEE

            HARLYN WETZEL CALLED IN THE REPORT

&&

VJENSEN

Local storm report, Aug 24, 1:19 PM CDT, 36 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BISMARCK ND
119 PM CDT THU AUG 24 2006

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

1150 AM     HAIL             LINCOLN                 46.77N 100.70W
08/24/2006  E1.25 INCH       BURLEIGH           ND   BROADCAST MEDIA

            MANY STONES WERE PEA TO MARBLE SIZE WITH A FEW STONES OF
            QUARTER AND HALF DOLLAR SIZE. REPORTED BY HUTCH JOHNSON
            OF KXMB-TV

&&

VJENSEN

Local storm report, Aug 24, 1:35 PM CDT, 20 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BISMARCK ND
135 PM CDT THU AUG 24 2006

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

1030 AM     HAIL             3 SE STANTON            47.29N 101.34W
08/24/2006  E4.00 INCH       MERCER             ND   PUBLIC

            SEVERE SIZE HAIL LASTED UNTIL 1100 AM CDT. LARGEST STONES
            GRAPEFRUIT SIZE. MANY VEHICLES DESTROYED. BUILDING
            SEVERELY DAMAGED. REPORT FROM GREAT RIVER ENERGY PLANT.

&&
LATE REPORT. NOTIFIED THROUGH LOCAL MEDIA. FOLLOW UP CALLS PLACED TO
GREAT RIVER ENERGY PLANT.

VJENSEN

Local storm report, Aug 24, 1:39 PM CDT, 16 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BISMARCK ND
139 PM CDT THU AUG 24 2006

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

0139 PM     FUNNEL CLOUD     12 NW GARRISON          47.78N 101.61W
08/24/2006                   MCLEAN             ND   LAW ENFORCEMENT

&&

VJENSEN

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.

Bismarck Municip, ND (KBIS), 12:00Z

6.9 hours before the tornado, 79 km from the path. August 24, 2006.

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: 2789 J/kg
Mixed-layer CIN: -137 J/kg
Surface CAPE: 1684 J/kg
Mixed-layer LCL: 568 m above ground
0-6 km bulk shear: 19 kt
0-1 km bulk shear: 22 kt
0-1 km storm-relative helicity: 55 m²/s²
0-3 km storm-relative helicity: 208 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 1.0
0-3 km lapse rate: 4.3 K/km

Open this sounding in Storm Lab

Bismarck Municip, ND (KBIS), 00:00Z

5.1 hours after it, 79 km from the path. August 25, 2006.

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

Mixed-layer CAPE: 0 J/kg
Mixed-layer CIN: -80787 J/kg
Surface CAPE: 187 J/kg
Mixed-layer LCL: 1048 m above ground
0-6 km bulk shear: 38 kt
0-1 km bulk shear: 17 kt
0-1 km storm-relative helicity: -43 m²/s²
0-3 km storm-relative helicity: -1 m²/s²
Significant tornado parameter: 0.0
Supercell composite: -0.0
0-3 km lapse rate: 6.0 K/km

Open this sounding in Storm Lab

The radar

The Bismarck radar (KBIS), 77 km away, was scanning. The volume nearest the touchdown began at 18:53 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)	Report	Where	County	Remark
15:58 UTC	HAIL 0.75	2 W Underwood	Mclean, ND	HAIL WAS ONGOING AND FALLING LIGHTLY
16:00 UTC	HAIL 1.75	1 E Hensler	Oliver, ND	SEVERE SIZE HAIL LASTED UNTIL 1115 AM CDT.
16:25 UTC	HAIL 0.75	Washburn	Mclean, ND	HAIL OCCURRING STILL AT 1127 AM CDT.
16:25 UTC	HAIL 1	Washburn	Mclean, ND	SEVERE SIZE HAIL 1125 AM CDT TO 1135 AM CDT...LARGEST STONES QUARTER SIZE. INFORMATION FROM WASHBURN WARNING POINT.
18:30 UTC	TSTM WND GST 60	10 N Zap	Mercer, ND	LASTED ABOUT 10 MINUTES
18:39 UTC	FUNNEL CLOUD	12 Nw Garrison	Mclean, ND
18:40 UTC	TSTM WND GST 70	Riverdale	Mclean, ND	BRANCHES BROKEN
18:45 UTC	FLASH FLOOD	Beulah	Mercer, ND	FLASH FLOODING OF LOW LYING AREAS WAS OBSERVED FROM BEULAH TO HAZEN. UNTIL 300 PM CDT. COUNTY ROADS FLOODED.
18:55 UTC	FLOOD	Beulah	Mercer, ND	FLOODING OF LOW LYING AREAS HAS BEEN REPORTED FROM BEULAH TO HAZEN
18:55 UTC	FLASH FLOOD	E Beulah	Mercer, ND	FLOODING RAINS FROM THUNDERSTORMS HAVE BEEN REPORTED IN LOW LYING AREAS FROM BEULAH TO HAZEN
19:05 UTC	TSTM WND GST 60	Washburn	Mclean, ND
19:10 UTC	TSTM WND GST 60	Garrison	Mclean, ND
19:12 UTC	HAIL 1	3 W Underwood	Mclean, ND	65 MPH WINDS ALSO REPORTED
19:20 UTC	TSTM WND DMG	5 Nw Washburn	Mclean, ND	FALKIRK NORTH DAKOTA. WIND ESTIMATED 90 MPH. SEVERE DAMAGE TO THE ELEVATOR AND VEHICLES. SEVERE WIND UNTIL 235 PM CDT. LATE REPORT.
19:20 UTC	TSTM WND GST 65	Underwood	Mclean, ND	REPORTED WINDS WERE ONGOING AT 222 PM CDT
19:28 UTC	TSTM WND GST 64	1 E Coleharbor	Mclean, ND	DAVIS WIND RECORDER.

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

This ground now

The live radar over the track Every 2006 tornado in North Dakota Every tornado in North Dakota since 1950 Warnings in force in North Dakota now The forecast where you are

The other tornadoes of August 24, 2006

14 more were confirmed in the United States that day.

Date	Time	Rating	Where	Path (mi)	Width (yd)	Deaths	Injuries	Damage
August 24	1:01 PM CDT	F0	Morton, ND	0.8	50			$40,000
August 24	4:00 PM EDT	F0	Martin, FL	0.3	30			$20,000
August 24	3:03 PM CDT	F0	Kidder, ND	1.0	40
August 24	4:40 PM CDT	F1	Sully, SD	5.0	600
August 24	5:03 PM CDT	F3	McPherson, SD	14.0	300		1
August 24	5:08 PM CDT	F0	Brown, MN	0.5	30		2	$200,000
August 24	5:13 PM CDT	F0	Hyde, SD	0.5	20
August 24	5:30 PM CDT	F3	Nicollet, MN	33.0	880	1	37	$24 million
August 24	5:33 PM CDT	F0	Hyde, SD	0.5	20
August 24	6:07 PM CDT	F2	Hand, SD	5.0	300
August 24	6:28 PM CDT	F3	Hand, SD	24.5	500		2	$15 million
August 24	7:18 PM CDT	F2	Beadle, SD	7.0	300			$2.0 million
August 24	7:23 PM CDT	F0	Beadle, SD	0.1	50
August 24	7:56 PM CDT	F0	Kingsbury, SD	0.1	50

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.