NWS Twin Cities Home Page » Historical Severe Weather Events » Sept. 21, 2005 North Metro Wind/Tornado Event
Storm Summary - September 21, 2005
Severe Thunderstorms produced a considerable amount of damage across central and east central Minnesota and west central Wisconsin during the evening hours on September 22.
Numerous reports of damaging winds, large hail, flash flooding and tornadoes were received at the National Weather Service in Chanhassen. A list of all storm reports received is available on our Local Storm Report.
Tornado Damage Survey Results
...Results from the Damage Survey for Tornadoes and Severe Thunderstorms in the Northern Twin Cities Metro Area on September 21st, 2005...
Storm damage was surveyed across portions of the northern metro for 2 consecutive days. On the first day, it was confirmed that 2 tornadoes and widespread downburst damage hit Andover, Coon Rapids and Blaine in Anoka County. The survey on the second day covered northern Hennepin and southern Anoka Counties. The storms moved east-southeast. The vast majority of damage in northern Hennepin County was due to downburst winds, mostly from the rear flank downdraft swinging around the south and west sides of the mesocyclone. A small and very brief F-0 tornado was also discovered to have touched down in the far northeast corner of Brooklyn Park, but the tornado damage paled in comparison to the damage caused by the downburst. The downburst winds were stronger and more widespread than the winds of the F-0 tornado. In fact, the downburst produced F-1 damage across much of northern Hennepin County, with a few roofs blown off in Brooklyn Park. Thousands of trees were toppled or snapped. The tornado did not cross the Mississippi River.
The storm moved from northern Hennepin County into southern Anoka County. Fridley was especially hard hit. The character of the storm also changed. There was some sporadic downburst damage in southern Fridley from the rear flank downdraft, but the mesocyclone itself (the center of the rotating storm) began producing damage on all sides. Perhaps the hardest hit area was the area between Fridley High School and University Avenue. Numerous trees were knocked down in all directions, with many landing on houses and vehicles.
One eyewitness described that trees were first knocked down toward the south. The intense wind continued but began changing directions. Then, what seemed like 3 or 4 minutes later, trees were being knocked down toward the northeast. The intense wind continued, still gradually changing direction. Finally, what seemed like several minutes later, trees were once again knocked down toward the south. This account is consistent with a mesocyclone moving overhead. There was very little major wind damage to any of the houses. Instead, the damage to houses was typically caused by falling trees. This suggests that winds were probably from 60 to 70 mph, but that winds were sustained for several minutes. One interesting noteis that the trees seemed to fall down in slow motion.
Furthermore, there was no indication of any distinct or concentrated damage path of particularly intense damage. Instead, the varying directions of toppled trees was exhibited over a diameter of 1 to 2 miles.
The rotating storm moved into Ramsey County. Numerous trees in New Brighton (just north of I-694 and Silver Lake Road) showed the same type of broad rotation damage pattern as in Fridley. Many trees were downed from New Brighton into Shoreview.
...Summary of Damage Surveys in Blaine and Andover...
The NWS storm survey team determined that a tornado touched down in the extreme eastern part of Coon Rapids... then moved into Blaine before dissipating just west of the National Sports Center. It was on the ground for 2 miles, tracking to the east-southeast. The tornado was rated an F-2 and had a maximum width of 50 yards.
The vast majority of damage in Andover was due to rear flank downdraft winds rotating around a mesocyclone. In fact, the downburst produced F-1 damage in Andover, across a large area. A tornado did touch down in Andover, but was rated only a F-0 and produced damage only over a small area. The Andover tornado had a maximum width of 25 yards and a path length of 0.3 mile.The tornado touchdown was just west of the intersection of 142nd Avenue NW and 143rd Avenuse NW.
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 Radar reflectivity image from 7:07 PM CDT on September 21, 2005. A brief F-0 tornado touched down in Brooklyn Park two minutes after this picture. Most damage in Hennepin County, however, was due to downburst winds. (Click for a larger image) |
 Radar reflectivity image from 7:16 PM CDT on September 21, 2005. A brief F-0 tornado was just touching down in Andover, and an F-2 tornado was about to touch down in Coon Rapids and move into Blaine. Most damage in Anoka County, however, was not tornadic. (Click for a larger image) |
 Radar reflectivity image from 7:24 PM CDT on September 21, 2005. The damage in Ramsey County was not tornadic. (Click for a larger image). |
The following images show where severe thunderstorms occurred (click on the images for a larger view):
 Summary of all severe thunderstorm reports from 9/21/05 |
 Preliminary tornado reports from 9/21/05 |
 Summary of large hail reports from 9/21/05 |
 Flash Flood reports from 9/21/05 |
 Summary of wind damage reports from 9/21/05 |
In addition to the severe weather reports, many locations received substantial amounts of rain. Many streets and underpasses in the northern Twin Cities metro area were flooded for a time Wednesday night. The following image is a storm total precipitation estimate from our radar in Chanhassen. The values in yellow are estimates of greater than 2.5 inches of rain, and the areas in orange may have received in excess of 3 inches of rain on Wednesday evening. Click on the image for a larger view.
Storm Damage Pictures
Here is a sampling of storm damage pictures sent in to the National Weather Service. More will be added in the coming days. Thanks to everyone who sent in photos. (Click on the images for a larger picture).
 Damage photo from south of Madison School in Blaine - by Rich Gudmunsen |
 Damage photo from south of Madison School in Blaine - by Rich Gudmunsen |
 Damage photo from south of Madison School in Blaine - by Rich Gudmunsen |
 Damage photo from south of Madison School in Blaine - by Rich Gudmunsen |
 Storm Approaching Brooklyn Park - by Scott Dier |
 Storm Approaching Brooklyn Park - by Scott Dier |
 2 foot diameter tree blown over in Rice Lake, WI - by Dirk Miller |
 Storm Damage in Andover - by S. Sullivan |
 Storm damage on 138th Avenue in Andover MN - by NWS Storm Survey Team |
 Storm damage on 104th Ct in Blaine, MN - by NWS Storm Survey Team |
 Storm damage on 104th Ct in Blaine, MN - by NWS Storm Survey Team |
 Storm Damage on East River Rd in Fridley, MN - by NWS Storm Survey Team |
 Tornado in Blaine, photographed from approximately 1/4 mile west of the National Sports Center. The tornado dissipated as it reached the photographer's location - photo by Brad Peterson |
 Photo taken in northeastern Brooklyn Park shortly before a tornado touchdown - Photo by Chandler Heath |
