National Weather Service United States Department of Commerce

Historical Low Pressure System Generates A Tornado,
Severe Winds and Record Low Pressure For Wisconsin

October 26, 2010

A record breaking low pressure system tracked northeast from the Central Plains on Monday, October 25, 2010, then moved across Minnesota through Tuesday, October 26. This system broke the record for the lowest sea level pressure measured in Wisconsin. This occurred at Superior, in far northwest Wisconsin, measuring 961.3 millibars (28.39") at 11:15 AM CDT on the 26th. The previous lowest sea level pressure recorded in Wisconsin was 963.4 millibars (28.45") at Green Bay on April 3 of 1982.



surface low animation
click for larger image loop
Satellite depiction of Low pressure system
click for larger image

The image above and to the right is a satellite image from NOAA-NASA GOES Project at 4:32 PM CDT on October 26. The MODIS true-color images from NASA's "Blue Marble" global map are used as a background, projected as though viewed from the GOES satellite location. Semi-transparent layers of GOES infrared and visible images are enhanced and layered on top of that color background.  NASA has a page dedicated to this storm.  



Did this storm break a national low pressure record? No.  Bigfork, Minnesota recorded the lowest pressure in the U.S. for this particular storm.  Bigfork had a minimum sea level pressure of 955.2 millibars (28.21") at 5:13 PM CDT. This set a new record low sea level pressure for Minnesota.  However, this turns out to be the second lowest sea level pressure for a non-tropical (extratropical) low pressure system in the Continental United States.  The National Climatic Data Center determined that the lowest CONUS, land-based, non-tropical, sea level pressure that can be confirmed is 955.0mb (28.20").  This occurred twice in United States history. The first time was on January 3, 1913 at Canton, NY.  The second was on March 7, 1932 at Block Island, Rhode Island.  These were verified by the NCDC using archived climate data publications.  Many storms have been discussed as potential record holders for the lowest recorded sea level pressure in a non-tropical storm at a land-based observing station in the Continental United States (CONUS). The lowest that has been mentioned was 951.6 millibars at Bridgehampton, NY on March 3, 1914. However, this value cannot be confirmed by records held at the National Climatic Data Center (NCDC).

For more details, please see the excellent write-up the NWS Duluth, MN office completed for this impressive Storm.



Tornado in Racine County

EF1 Tornado (Enhanced Fujita Scale) from just south of the Kenosha/Racine County line near Somers to near Graceland Cemetery in the city of Racine. 

  • Tornado path was 6.35 miles in length 
  • Max width 75 yards
  • Winds around 105 MPH
  • Started at 7:47 AM, about 1.8 miles NNE of Somers and traveled 0.43 miles to the Racine/Kenosha county border.
  • Ended at 7:53 AM, about 2.2 miles W of Downtown Racine after traveling 5.92 miles through Racine County.

A thunderstorm along a cold front spawned a fast moving and short-lived tornado Tuesday morning from Somers in Kenosha County to Graceland Cemetery in the city of Racine. Strong low level wind shear was the major ingredient for the threat of tornadoes Tuesday morning. The tornado caused numerous uprooted trees, numerous snapped and downed power poles, roof damage to the Case and old Sapko buildings. Several doors were blown off the Case building. Several parked tractor trailers tipped over, a barn was blown off its foundation, and a 6 car garage was destroyed. Other minor structural damage occurred throughout the path of the tornado. The path of damage became more sporadic and less severe after the tornado passed the Case building, dissipating near Graceland Cemetery.  

image of the tornado path
click for a larger image
loop of doppler radar imagery
click for a larger image

The image on the left is a plot of tornado path and the associated damage locations.  On the right, is the radar loop from the Terminal Doppler radar (TMKE) showing an up close look at the storm that produced the tornado. The entire life cycle of the thunderstorm was about 6 minutes and the rotation spun up quickly and dissipated quickly. By the time the tornado showed up on radar (rotation in the velocity data), the tornado was already on the ground. 

Storm Damage Survey Photos: (click on pictures for a larger image)

First sign of tornado damage at a farm near County Road KR and County Road EA in Kenosha County

garage destroyed   part of garage damaged nearby vehicle  

parked tractor trailer overturned  parked tractor trailer overturned


Tornado damage to the old Sapko industrial building near the intersection of Hwy 11 and Oakes Rd in Mt Pleasant (Racine County)

old Sapko building   damage to the loading area on southwest side of bldg   damage to HVAC units on top of Sapko bldg

A house and barn sustained tornado damage along Hwy 11 near Oakes Rd. 

house on Hwy 11 and Oakes sustained roof damage   barn blown off its foundation  

barn blown off foundation   trees snapped and uprooted near Hwy 11 and Oakes Rd

The Case manufacturing plant in Mt Pleasant (Hwy 11 and Oakes Rd) sustained damage to several garage doors and the roof.  It also overturned a parked semi trailer.

power lines down along Hwy 11 near Case   roof damage from inside Case plant  

roof damage at Case plant   tractor trailer overturned at Case plant

The tornado weakened shortly after it hit the Case plant, but continued to produce more sporadic damage to trees and power poles along its track into Racine.  It appeared to have dissipated near the Graceland Cemetery in Racine. 

If you have any damage photos and wouldn't mind having them displayed on our website, please send them to us at:



Severe, Non-thunderstorm Winds

The intensity of this historic low pressure system created a very tight pressure gradient across much of the Upper Midwest and the Great Lakes.  The pressure gradient is the change in pressure across a region. In this case, from the low center over Minnesota to the high pressure axis located over the southern tier of the United States.  The air flows from high pressure to low pressure and the tighter the pressure gradient, the stronger the wind.  It should be noted that although the low pressure system for the October 26th storm was deeper/stronger than the low pressure system from the comparable, but weaker storm on November 10, 1998, the winds during the November 10th storm were stronger.  This was due to a much stronger high pressure system to the south that set up an even stronger pressure gradient across our area, despite the weaker low pressure system.

After a cold front swept through the area during the early morning hours on Tuesday, October 26th, winds begain to increase very rapidly out of the southwest.  What was unusual about this storm was it slow movement and persistent strength.  By the next day, Wednesday, October 27, the low had weakened only slightly while drifting slowly north into Canada, and the high pressure to the south increased in strength.  This resulted in a very tight pressure gradient over the region for another day, generating strong and damaging winds on Wednesday. 

Below is a list and graphic of the strongest winds recorded during the day on Tuesday, October 26, 2010  

Kenosha Airport** 68 mph**
Sheboygan (C-man station) 68 mph
Pardeeville 61 mph (estimated)
Milwaukee Airport 61 mph
Sheboygan Airport 59 mph
Elkhorn ( Walworth County) 59 mph
Milwaukee (C-man station) 59 mph
Lodi (Columbia County) 58 mph
Random Lake (Sheboygan County) 57 mph
Shorewood Hills (Dane County) 57 mph
Governor Dodge St Park (Iowa County) 56 mph
Darlington (Lafayette County) 55 mph
Monroe Airport 55 mph
Fort Atkinson (Jefferson County) 55 mph
Elm Grove (Waukesha County) 55 mph
West Bend (Washington County) 55 mph
Mineral Point Airport 54 mph
Racine 54 mph
Kenosha (C-man station) 54 mph
Knowles (5 mi west) (Dodge County)  53 mph (estimated)
Fond du Lac Airport 53 mph
Princeton (Green Lake County) 53 mph
Cedarburg (Ozaukee County) 51 mph
Janesville Airport  51 mph
Lone Rock Airport 51 mph

 **Kenosha 68 mph wind gust occurred with a thunderstorm early in the morning - a 56 mph gust was reported later in the day

plot of highest winds 


Below is a list and a graphic of the strongest winds recorded on Wednesday, October 27, 2010



63 mph
Brown Deer (Milwaukee County) 63 mph
Berlin (Green Lake County) 62 mph
Bear Valley (Washington County) 62 mph
Sheboygan 62 mph
Knowles (5 mi west) (Dodge County) 61 mph (estimated)
Monroe Airport (Green County) 61 mph
Milwaukee Airport 61 mph
Waterford (Racine County) 61 mph
Germantown (Washington County) 61 mph
Sheboygan Airport 60 mph
Slinger(Washington County) 60 mph
Byron (Fond du Lac County) 60 mph
Baraboo (Sauk County) 60 mph
Lodi (Columbia County) 59 mph
Racine Airport 59 mph
Elkhorn (Walworth County) 59 mph
Cedarburg (Ozaukee County) 59 mph
Kenosha Airport 58 mph
Jackson (Washington County) 58 mph
Juneau (Dodge County) 58 mph
Mineral Point (Iowa County) 56 mph
Brookfield (Waukesha County) 56 mph
Milwaukee Timmerman Airport 55 mph
Packwaukee (Marquette County) 55 mph
Shorewood Hills (Dane County) 55 mph
West Bend (Washington County) 55 mph