October 26, 2010 - Record Low Pressure, Tornado, Severe Winds

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.

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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.  

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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

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

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

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: w-mkx.webmaster@noaa.gov

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

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