Eleven tornadoes moved through parts of North Dakota, South Dakota, and Minnesota on August 26, 2007. Four of these came from two merged supercells in North Dakota. Three were significant (EF2+), the only strong tornadoes of the day. This summary documents those three and focuses on the community of Northwood and their experience with a devastating EF4. This was the first F/EF4 in North Dakota since the July 18, 2004, Marion event, and the last until June 17, 2010.

An enormous thanks to the Warning Coordination Meteorologist of the National Weather Service in Grand Forks, Greg Gust. Greg warned, surveyed, and rated all of the tornadoes in this summary, and knows more about them than anyone else. He collected and provided me with all the detailed information he could find, and much of what is in this summary is sourced from him. Greg also appeared on a Tornado Talk podcast on the Northwood tornado shown below. Thank you as well to all of the NWS staff involved in the surveying.

A GIF showing the evolution of the two merging thunderstorms that would produce the strongest tornadoes of the outbreak. Click on image to play (Greg Gust/NWS).
A wide view of the three significant tornado swaths.

Rugh Lake, ND

SPC Stats

Path length: 6 miles

Width:  580 yards

Fatalities:  0

Injuries:  0

Rating:  EF3

County:  Nelson, Grand Forks

The first tornado of the day began about six miles to the north-northeast of Aneta, in Nelson County. It tracked to the north-northeast at an average speed of about 33 mph – somewhat fast for strong tornadoes in the High Plains. Within two miles, the tornado reached its peak intensity of EF3 with a maximum width of 710 yards (or about 2/5ths of a mile). Numerous trees were snapped or uprooted. A swathing combine was completely dismantled, and several empty metal grain bins were torn from their anchors. The grain bins were so cleanly demolished they were reported as “missing.” A garage and outbuildings at three farmsteads were swept away. Gravel roads were deeply scarred by debris, and some scouring of surface vegetation occurred. Five buffalo were violently killed by the tornado, the carcasses strewn across torn-up fields. Video taken nearby showed evidence of tightly clustered suction vortices embedded within the main funnel. After crossing into Grand Forks County where a second combine was lofted and destroyed, the tornado abruptly dissipated. It ended a mere twelve minutes after formation with a path six and a half miles long. Peak winds were estimated at 150 mph.

There is a curious story about the home with the garage swept away. That same home had been hit by a tornado three years earlier and rendered uninhabitable. The family who lived there moved to a very unfortunate location. That location was Northwood. 

Tornado Path

Click map to enlarge

SPC coordinates:  Start: 47.76 / -97.93   End:  47.48 / -97.84

Corrected coordinates based on Greg Gust’s maps:  Start: 47.760048 / -97.938426   End:  47.843547 / -97.875802

Note:  Exact tornado path may not be straight and/or continuous.

Images of Damage

Minor ground scarring early on in the tornado track. A piece of a combine can be seen in the distance (Greg Gust/NWS).
A garage that was destroyed (Greg Gust/NWS).
Bin pads left by the tornado (Greg Gust/NWS).
Where the tornado crossed a road, with a dead buffalo in the distance (Greg Gust/NWS).
Dead buffalo along the tornado’s track (Greg Gust/NWS).
The tornadic polygon overlaid on Landsat satellite imagery taken ten days later shows the scarring of the landscape.

Video

Northwood, ND

SPC Stats

Path length: 5 miles

Width:  1400 yards

Fatalities:  1

Injuries:  18

Rating:  EF4

County: Grand Forks

The most powerful tornado of the day formed three miles to the west-southwest of Northwood in Grand Forks County at 8:42 p.m. CDT. While initially weak and narrow, the tornado began to grow and intensify as it crossed the Goose River, where a 200 yard wide stretch of downed trees was left. The tornado was 550 yards (about a third of a mile) wide when it struck the Northwood airport. Here, a plane hangar was removed at EF1 intensity and small airplanes were destroyed. Three-quarters of a mile further northeast the tornado would enter Northwood. It was already 900 yards (a half-mile) wide and would continue to grow.

Northwood mayor Rick Johnson had been more worried about hail damage to the cars at his dealership than the tornado. After moving his cars into an indoor shelter he headed home for what should have been the night. He had been home no more than 30 seconds before hearing a loud rumble, with tree branches beginning to blow about.

Dave Korsmo was also aware of the impending severe weather and went to check on his mom and dad. He had just gotten into their house when they received the tornado warning alerts. He gathered everyone into the home’s basement area just before the tornado struck.

Several neighborhoods on the southwestern side of the town sustained up to EF2 damage with roofs torn off and trees snapped or uprooted. The tornado would keep a gradual northeastward curving track and continued to strengthen, making a direct strike on the Northwood Public School. That structure sustained irreparable EF3 damage and was later torn down. Surveyor Greg Gust noted that the damage indicated a clear multi-vortex pattern, with separate streaks of intense damage embedded within a vast swath of lighter damage.

The tornado then tore through the business district. Large retail and even brick buildings were severely damaged or destroyed. This included the local health center, a bank, a supermarket, and a new fire station. A large wooden grain elevator belonging to Northwood Equity Elevator sustained severe damage. This is what Greg Gust told me when I asked about the damage to this structure and surrounding areas: “The wooden grain elevator, top portions torn off. From the wood frame boot shelter at the very top, down maybe 20 feet into the 2×6 (six inch solid walls) flat nailed and interlaced storage portion. A grain car full of wheat was parked on the tracks nearby and thrown some 40 feet westward… No DI (Damage Indicators, used to rate tornadoes on the EF scale) really spoke to these issues. A well built wooden grain elevator is incredibly tough.”

A final neighborhood was struck as the tornado moved through the northeastern portion of Northwood. Sadly, the tornado turned deadly here. 57-year-old Larry Weisz was killed when he was pinned between a tree and the base of a mobile home. Damage appeared to be more consistently stronger as the tornado left the residential outskirts, with a shelterbelt sustaining severe denuding and minor debarking of trees.

The now rain-wrapped tornado continued to intensify as it traveled another half of a mile beyond the outskirts of the town proper. There, it reached a maximum width of 1400 yards (4/5ths of a mile). EF4 damage was noted in this area to multiple structures, caused by a particularly intense subvortex. Most of the building which housed the agricultural company Agvise Laboratories was leveled to the ground. It was well constructed, Greg describing it as the equivalent of a two-story office building with part consisting of larger bay laboratory areas. Two well constructed MBS (Metal Building System) buildings belonging to Gabriel Construction were located in this area. The first was severely damaged and partially destroyed. The second was completely leveled and mostly swept from the slab. The trees surrounding the second MBS were also removed. Because of the contextual damage to this building, it was rated EF4 rather than a typical maximum rating of high-end EF3. Nearby low lying shrubbery was denuded and partially debarked, and steel beams from the building were twisted and tossed. Massive metal tanks from this company were picked up and hurled; one traveled a mile, the other one and a half miles. Gravel trucks at the business were swept away and mangled, one being tossed hundreds of yards across the highway. 18 cars had been parked in Rick Johnson’s adjacent car dealership parking lot; many were damaged beyond recognition. Some had even been thrown a half mile or more into fields. Either a small sugar beet or soybean field immediately north of Gabriel Construction was thoroughly scoured to only soil.

The damage to strong, fully mature corn from this tornado was highly impressive. To the northwest of Gabriel Construction on the other side of the road was a cornfield. Here, fully mature corn plants were stripped and snapped several inches above the roots and flattened into the soil. Any pieces of corn that could be found had been husked by the extreme winds and often sliced into chunks. Photographs indicate there was at least one smaller area where corn was scoured until very little but the ground was left.

Greg Gust at the NWS directed ambulances dispatched from Grand Forks out of the way of the storm as they almost drove into the path of the tornado. Fortunately, the extreme intensity would not last for long. Curving abruptly to the east-southeast, the tornado dramatically weakened, dissipating only two and a half miles to the east-northeast of the town at 8:54 pm CDT. It had existed for only twelve minutes with a path length roughly six miles long and an average forward speed of 30 mph.

Back in Northwood, mayor Rick Johnson got in his car and turned the corner onto Main Street. He was stunned by his first look at what had happened to his town. Rick made his way to city hall to get a handle on what had happened. Within about an hour search and rescue began. The house Dave Korsmo had sheltered in sustained little more than broken windows, but many were not so lucky. In the town of roughly 950 people, 431 out of 460 homes had been impacted by the tornado. 57 of those were destroyed. Just one day before school started the town’s grade school had been destroyed. Advance warning of the tornado had kept the human toll quite low for such an event. Nevertheless, one had been killed, 18 more injured, and 60-62 million dollars in damage done. In the end, 2600 truckloads of debris would be removed to the town landfill.

Northwood made a full recovery. The National Guard arrived in town 15 hours after the event and left five days later. The largest employers of the town whose buildings were destroyed all decided to stay and rebuild. This was a blessing for Northwood, as people needed the income from those jobs more than ever. Over the following summer, Greg aided the Northeast Human Services Group in conducting several meetings to help kids openly discuss their feelings, thoughts, and fears after the disruption and trauma the event had caused. Lessons learned from the debris removal process at Northwood by the North Dakota State Department of Health and Division of Waste Management has led to changed guidelines to help assisting communities in disaster recovery.

Tornado Path

SPC coordinates:  Start: 47.72 / -97.61   End:  47.74 / -97.53     

Corrected coordinates based on Greg Gust’s maps:  Start: 47.715263 / -97.625278   End:  47.741877 / -97.515825     

Note:  Exact tornado path may not be straight and/or continuous.

Photos

A GIF created from radar images of the Northwood tornado provided by Greg (Greg Gust/NWS).
A GIF of the life cycle of the Northwood tornado in 3D velocity created from images provided by Greg (Greg Gust/NWS).
Debris trajectories in the area of the airport as mapped by Greg (Greg Gust/NWS).
Debris trajectories in the area northeast of Northwood as mapped by Greg (Greg Gust/NWS).
A slabbed hangar at the Northwood Airport (Greg Gust/NWS).
An aerial view of damage to the airport (Greg Gust/NWS).
Housing damage in southwestern portions of Northwood (Greg Gust/NWS).
Damage to Northwood’s grade school (Greg Gust/NWS).
A wide view of damage to and around the school (Greg Gust/NWS).
An aerial view of damage in the center of town (Greg Gust/NWS).
A collapsed building in downtown (Greg Gust/NWS).
An aerial view of damage along the railroad (Greg Gust/NWS).
Damage to the grain elevator (Greg Gust/NWS).
An aerial view of damage to the grain elevator (Greg Gust/NWS).
An aerial view of severe damage to an apartment (Greg Gust/NWS).
An aerial view of residential damage in the northeastern portions of town (Greg Gust/NWS).
An aerial view of damage at a trailer court. This is where the fatality occurred (Greg Gust/NWS).
Damage to a shelterbelt as the tornado exited the town proper (Greg Gust/NWS).
An aerial view of damage to Agvise Laboratories (Greg Gust/NWS).
The front sign of Agvise Laboratories was left seemingly intact just outside the worst damage swath (Greg Gust/NWS).
Extreme damage to Agvise Laboratories (Greg Gust/NWS).
A metal-frame building that was slabbed near Agvise Laboratories (Greg Gust/NWS).
A bent anchor on the slab of a metal-frame building (Greg Gust/NWS).
An aerial view of the damage to Gabriel Construction. One MBS was left severely damaged; just above it is the foundation where another once stood (Greg Gust/NWS).
Damage to Gabriel Construction (Greg Gust/NWS).
Damage to Gabriel Construction (Greg Gust/NWS).
Damage to Gabriel Construction (Greg Gust/NWS).
Damage to Gabriel Construction (Greg Gust/NWS).
A gravel truck that was destroyed at Gabriel Construction (Greg Gust/NWS).
A massive metal tank hurled one mile from Gabriel Construction (Greg Gust/NWS).
A massive metal tank hurled a mile and a half from Gabriel Construction (Greg Gust/NWS).
Low lying vegetation adjacent to the swept away building at Gabriel Construction was denuded and partially debarked. In the background cars from Rick Johnson’s dealership were hurled into a field and severely mangled. The field they are lying in was scoured of either sugar beet or soybean (Greg Gust/NWS).
Mangled cars from the car dealership. The one closest to the camera was once a Toyota Tacoma. The field they are lying in used to be sugar beet or soybean, which was entirely removed (Greg Gust/NWS).
Fully mature corn snapped off several inches above the roots and flattened into the soil in a circular pattern. More cars thrown from the dealership can be seen in the background (Greg Gust/NWS).
Two vehicle frames that were smashed together (Greg Gust/NWS).
A severely mangled car in a shredded cornfield. Pieces of stalks or even their leaves appear to be embedded in portions of the vehicle (Greg Gust/NWS).
The tornadic polygon overlaid on Landsat satellite imagery taken ten days later shows the scarring of the landscape.
An image showing the mostly rain-wrapped tornado dissipating after striking Northwood. Taken by Aaron Kennedy (Greg Gust/NWS).

Photos via Flickr

Crumpled
Corn Field

Video via Greg Gust

Youtube Videos

Newspaper Clippings

Eldred, ND/MN

SPC Stats

Path length: 6 miles

Width:  580 yards

Fatalities:  0

Injuries:  0

Rating:  EF2

County:  Grand Forks (ND), Polk (MN)

The last significant tornado of the day began roughly seven miles to the east-northeast of Reynolds in Grand Forks County. It immediately produced EF1 damage within a couple hundred yards of the starting point. An antique wind charger mill was wrecked and some trees were downed. After tracking for two and a half miles, the tornado crossed the Red River into Polk County, MN.

Immediately after crossing the river, the tornado intensified to EF2 intensity, which it would hold as two farmsteads were impacted. Power poles were snapped and a communications tower was brought down. Damage also included the destruction of both a steel pole shed and a wooden quonset. Significant tree damage was noted along the track. Two and a half miles after crossing the river, the tornado made a sudden northward turn. Curving further around to the west, a farm was struck at EF1 intensity. The tornado dissipated soon after with a path length slightly over six miles. Only two damage photographs remain both of which are shown below.

Tornado Path

Click map to enlarge

SPC coordinates:  Start: 47.72 / -96.96   End:  47.72 / -96.86      

Corrected coordinates based on Greg Gust’s maps:  Start: 47.696543 / -96.963699   End:  47.715521 / -96.873494      

Note:  Exact tornado path may not be straight and/or continuous.

Damage Photographs

An antique wind charger mill that was bent and collapsed by the tornado in Grand Forks County (Greg Gust/NWS).
Minor tree and roof damage in Grand Forks County (Greg Gust/NWS).

Discrepancies:

We gathered information for this event from the SPC & NCDC Databases, the August 2007 Storm Data Publication, The NWS Grand Forks event page, and personal communications with the WCM from NWS FGF, Greg Gust, and found the following differences:

Rugh Lake Tornado

Path Length:

– The SPC and NCDC coordinates do not align with the verifiable tornado polygon created by Greg Gust. Their coordinates are 720 yards too far east at the start, and 1.68 miles too far to the east-southeast at the end.  
– The Nelson/Olmsted County border coordinates in the NCDC database entries are 0.8 miles northwest/southeast of each other. 
– The path length from the SPC, SDP, NCDC, and NWS Grand Forks is 6 miles. The centerline of the tornadic polygon created by Greg Gust measures 6.53 miles.  

Width:

– The SPC, SDP, NCDC, and NWS Grand Forks maximum width is 580 yards. Measuring the tornado polygon created by Greg Gust shows a maximum width of 710 yards, which is more reasonable relative to the scouring swath visible on Landsat satellite data. 

Northwood Tornado

Path Length:

– The SPC, SDP, NCDC, and NWS Grand Forks coordinates do not align with the verifiable tornado polygon created by Greg Gust. Their starting point is 1380 yards too far to the east-northeast and ending point 1200 yards too far to the west-southwest.
– The path length from the SPC, SDP, NCDC, and NWS Grand Forks is 5 miles. The centerline of the tornadic polygon created by Greg Gust measures 5.96 miles. 

Eldred Tornado

Path Length:

– The SPC and NCDC coordinates do not align with the verifiable tornado polygon created by Greg Gust. Their starting point is 1.65 miles too far to the north and ending 1250 yards too far to the east-northeast. 
– The state border coordinates between North Dakota and Minnesota are somehow 1.4 miles north/south of each other. In addition, neither are along the damage path. 
– The path length from the SPC, SDP, NCDC, and NWS Grand Forks is 5 miles. The centerline of the tornadic polygon created by Greg Gust measures 6.22 miles. 

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