2007_08_26_NorthwoodTornado

Select Tornadoes:

2 Weak Tornadoes - Union/Hoople ND Cavalier, Pembina, and Walsh Counties Date 26 August 2007 Time (Local) 6:55 - 7:07 pm CDT and 7:20 - 7:30 pm CDT  EF Rating EF0 and EF1 Est. Peak Winds 70 mph and 90 mph Path Length 5.0 miles and 5.5 miles Max Width 30 yds and 100 yds Injuries/Deaths 0 deaths or injuries Summary: In far northeast ND... an early evening supercell spawned 2 consecutive weak tornadoes which tracked eastward across far southeast Cavalier County into far southwest Pembina County, and from southwest Pembina County into northcentral Walsh County. Tornadic storms continued forming and tracking eastward into far northwest MN. Early Tornado Warnings issued by WFO Grand Forks Tornado Warnings as issued for the first two tornadic storms, in far northeast ND.

Tornado #1 viewed west of Gardar ND, photo courtesy if J. Johansen. Tornado #1 track passing just north of Union, ending west of Gardar ND.  Tornado #2 viewed from Park River ND, photo courtesy of B. Nelson. Tornado #2 track ending just west of Hoople ND.

2 Weak Tornadoes - near Napoleon ND Logan County Date 26 August 2007 Time (Local) 8:05 - 8:20 pm CDT and 8:35 - 8:40 pm CDT EF Rating Both rated EF0 Est. Peak Winds 70 to 75 mph Path Length 6.2 miles and 0.5 miles Max Width 75 yds and 30 yds Injuries/Deaths 0 deaths or injuries  Summary: In south-central ND...one supercell produced two distinct tornadoes, each of which touched down briefly and intermittently, damaging trees and straw bales. This supercell also produced quite a bit of very large hail (3 inch diameter) across the area. Tornado Warnings issued by WFO Bismarck Tornado Warnings as issued by WFO BIS for the supercells firing in far southern ND.

Tornado #5 viewed north of Napoleon ND, photo courtesy of R. Rattei. Tornado #6 northeast of Napoleon ND, photo courtesy of R. Rattei. Large hail which fell near Napoleon ND, photo courtesy of R. Rattei. Tracks for Tornado #5 and #6 near Napoleon ND.

Severe (EF3) Tornado - Rugh Lake ND Nelson County Date 26 August 2007 Time (Local) 8:04 - 8:16 pm CDT EF Rating EF3 Est. Peak Winds 150 mph Path Length 6.0 miles Max Width 580 yds Injuries/Deaths 0 deaths or injuries Summary: In east-central ND... this first supercell, and the first tornado it produced (Tornado #4 of 11), lifted northeastward from southeast Nelson County into southwest Grand Forks County. This supercell then passed to the north of Northwood and produced a second distinct tornado (Tor #9 of 11) south of Merrifield, or just southwest of the city of Grand Forks, between 9:15 and 9:30 pm CDT. Rugh Lake Tornado Video This video, by NWS Cooperative Observer Larry Lokken, shows the development of the Rugh Lake Tornado. Note the multiple vortices evident near the base of the mature tornado (~1 minute mark).

One farmstead where sheds, barns, and grain bins were all destroyed. This farmstead had been hit by a tornado 2 years earlier which had severely damaged the farmhouse.  The Rugh Lake Tornado killed 5 buffalo that had been out grazing, and annihilated adjacent pasture and corn fields.  Tornado #4 beginning east of Rugh Lake and tracking to the NNE for roughly 6 miles... just across the Grand Forks County line.  Tornado Warnings as issued by WFO FGF for supercells which produced at least 4 tornadoes, including the Rugh Lake EF3 and the Northwood EF4 Tornado.

Devastating (EF4) Tornado - Northwood ND Grand Forks County Date 26 Aug 2007 Time (Local) 8:42 to 8:54 pm CDT EF Rating EF4 Est. Peak Winds 170 mph Path Length 5 miles Max Width 1400 yds Injuries/Deaths 1 death, 18 injuries Summary: One of the several supercells which formed and tracked from east-central ND into northwest MN produced this tornado, number 7 of the 11 which occurred across the two states. These storms also produced the three strongest tornadoes of the day, including the EF3 Rugh Lake and EF4 Northwood Tornadoes.  All Tornado Warnings issued across ND and MN for this Episode A total of 13 Tornado Warnings were issued during this episode. A total of 11 distinct tornadoes were documented in all but 2 of these polygons. Many additional areas received Severe Thunderstorm Warnings for large hail and damaging wind.

Of the three supercells evident here at 01:11z (8:11 pm CDT), Cell A was dissipating and did not produce a tornado, Cell B was producing the Rugh Lake Tornado, and Cell C was intensifying before it eventually formed the Northwood Tornado. This image captured by storm chasers shows one of the brief vortex tubes or funnels which formed around 8:27 pm CDT, in the very unstable airmass bordering Nelson, Grand Forks, and Steele Counties. Photo courtesy of A. Kennedy. Eventually a much stronger funnel and subsequent tornado formed WSW of Northwood and tracked up through the community, lasting for a total of about 12 minutes. As with most tornadoes, not all areas in it's path were subjected to the same intensity or duration of winds.   This image captured by storm chasers, located ESE of Northwood near Hwy 18, shows the updraft area (back end) of the storm with a largely rain wrapped tornado as its lifting away from the community. Photo courtesy of A. Kennedy.

The Enhanced Fujita (EF) Scale classifies tornadoes into the following categories:

EF0 Weak 65-85 mph	EF1 Moderate 86-110 mph	EF2 Significant 111-135 mph	EF3 Severe 136-165 mph	EF4 Extreme 166-200 mph	EF5 Catastrophic 200+ mph

In Depth: Northwood ND Tornado rated EF4
 

The NOAA/NWS Grand Forks Storm Damage Assessment Team rated the large mulit-vortex tornado which struck Northwood North Dakota on Sunday August 26, between 8:45 and 8:50 pm, as an EF4 on the Enhanced Fujita (EF) Scale. Damage in the northeastern corner of the community indicated top wind speeds of up to 170 mph, which is in the lower end of the EF4 scale.
 

Nearly all of the community of Northwood was impacted by the tornado which reached an impressive width of about eight tenths of a mile as it pushed through town. Total length of the tornado was estimated to be about 5 miles, beginning 2 miles west southwest of town, and extending 2 miles east-northeast of town.

The main residential areas and business areas of the town received widespread EF2 to EF3 damage, with peak winds of 120-150 mph. The most intense damage was evident in the northeast corner of town where open space allowed an especially strong suction vortex to scour to ground level, flattening fields and wrapping or carrying debris and heavy projectiles in wide arching patterns.

In the northeast part of town, the Agvise Laboratories and Gabriel Construction buildings were a total loss. Cars, trucks, semi tractors and trailers became projectiles and were carried one half mile or more into corn and bean fields which were also scoured to the ground.

Sadly, the Northwood Tornado did result in one fatality and some 18 injuries.  

Is this Common?  Previous to this event, the most recent EF4 tornado in North Dakota had been the July 18th, 2004, tornado which struck the far southwest corner of Barnes County, near the towns of Marion and Litchville.

Since this event (through Aug 2017), there have been four more EF4 rated tornadoes in the local warning area, including 3 on June 17, 2010 [near Wadena MN, Almora-Bluffton MN, and Mayville-Holmes ND], and 1 on Aug 7, 2010 (near Tyler ND to Doran MN).  Plus there have been 2 more in SD and 1 more in southern MN. 

A average sized county in the eastern Dakotas or western Minnesota will have, on average, one tornado per county per year. Most of these will be weak, of the EF0 to EF1 range, though this same area can expect to see at least one EF3 or stronger tornado each year. 

Isn't this late for such a Strong Tornado?  It is common to have strong (EF2/EF3) tornadoes in late August, even into September and October, in North Dakota and northern Minnesota.  Multiple late season tornadoes struck near Bismarck back on November 1st of 2000, but they were weak (EF0/EF1).  However, the Northwood tornado is the latest in the convective season that a tornado of EF4 intensity has struck anywhere in either North or South Dakota.  Previous to this event, the latest EF4 tornado was near Medina ND, on August 11, 2002.  The latest a devastating (EF4) or higher tornado has struck anywhere the tri-state area was in Olmstead County MN (near Rochester), back on September 16th, 1962.   

Are all Strong to Devastating Tornadoes also Killer Tornadoes?  Any tornado could be a killer tornado, depending on what people are able to use for shelter! The most tornado fatalities ever to occur in our eastern North Dakota warning area, and in the State of North Dakota as a whole, were the 12 deaths attributed to the Fargo June 20, 1957, tornado.  More recently there was 1 death in Cavalier County ND in 1966.  In northwest Minnesota,  2 fatalities occurred in Polk County in 1975 and 1 fatality occurred in 1978, and Ottertail County had 1 tornado fatality in 1987.  Most recently, there were three fatalities which occurred in Minnesota during the 17 June 2010 Tornado Outbreak, 1 near Mentor (Polk County), 1 near Almora (Ottertail County), and 1 near Conger (Freeborn County).  The most tornado fatalities to occur in our northwest Minnesota warning area, second highest for the state of Minnesota as a whole, were the 57 fatalities attributed to the tornado which struck Fergus Falls MN (in Ottertail County) back on June 22, 1919.

Check additional tabs for a detailed look at the Northwood Tornado track, related damage photos, related radar imagery, and a summary of area storm reports. 

For more information please contact the NOAA/NWS Grand Forks ND, at 701-772-0720.

Track Segments and Damage Photos:

Segment 1: Touchdown-airport-edge of town

Track and debris scatter pattern as tornado approaches town from the southwest.	Aerial image of the airport showing damaged structures.  (photo: GF County EM)	Early damage as tornado enters town, removing trees, garages, and sections of homes. (photo: NWS survey)	Numerous free standing and attached garages were completely torn away. Failure of an attached garage will often lead to more extreme home damage. (photo: NWS survey)

Segment 2: Expansion over the center of town

The tornado track widened considerably as it moved over the townsite. Within the affected area, damage varied considerably due to exposure to variations in intensity and duration of the sub-vortices.	The New FireStation, which had hosted a SkyWarn Spotter Class about one year earlier, was completely destroyed.  (photo: GF County EM)	Damage at this apartment shows the progression from EF2 to EF3, as the roof is completely removed and exterior wall start to collapse.  (photo: GF County EM)	At the grain elevator, large metal bins were crushed, the upper section of the elevator was torn off, and full grain cars were tumbled over.  (photo: GF County EM)

Segment 3: Drilling into the northeast corner

At the northeast corner of town, rough debris trajectories indicated a strengthening suction vortex an higher scale damage than adjacent areas.	The Agvise Laborory facility, including two-story offices, adjacent labs and detached storage structures was completely demolished. (photo: GF County EM)	The Gabriel Construction facility had one structure completely removed and the other severely damaged. Trees were sheared off and heavy equipment was tossed around.  (photo: GF County EM)	Numerous vehicles which were stored in buildings near Agvise Lab were thrown or tumbled downstream a half mile or more... after their storage structure was demolished.  (photo: NWS survey)

Radar Depictions:

KMVX 0.5 degree Base Reflectivity and Base Velocity images

Dual Ref-Vel image at 840 pm CDT, touchdown southwest of town.	Dual Ref-Vel image at 845 pm CDT, intensify through the airport.	Dual Ref-Vel image at 849 pm CDT, debris ball evident over town.	Dual Ref-Vel image at 853 pm CDT, peak velocity NE of town.

KMVX Velocity Cross-Sections showing descending Rear Flank Downdraft

Vel cross-section at 840 pm CDT, bright green descending RFD (Rear Flank Downdraft), bright red shows inflow and updraft.	Vel cross-section at 845 pm CDT, RFD still increasing, dull green shows FFD (Forward Flank Downdraft).	Vel cross-section at 849 pm CDT, multiple RFD plumes descend, multiple tornado vortices.	Vel cross-section at 853 pm CDT, RFD corresponding to maximum near surface peak velocity couplet.

Storm Reports

For a listing of the Preliminary Storm Reports collected from August 26, 2007, check out the listing compiled by the NWS Storm Prediction Center at: http://www.spc.noaa.gov/climo/reports/070826_rpts.html.