June 6, 2006 Tornadoes Across South Central Wisconsin


A broken line of thunderstorms, with embedded supercells, moved east-southeast across Wisconsin during the evening hours of June 6, 2006. These thunderstorms were associated with a cold front that trailed from a low pressure system that move east across the area just north of Lake Superior. Three tornadoes spun up in the County Warning Area of the Milwaukee/Sullivan NWS office: two F0's in Iowa County and one F1 in Columbia County. The Columbia County tornado moved through the northeast corner of Sauk County northeast of Baraboo (along the Wisconsin River).  

Spotter reports and pictures indicated that the cloud bases were low.  In addition, there was very low development of cloud material (condensation) associated with the rotating wall cloud features. At times, multiple vortices were noted with the tornadoes in both Columbia and Iowa County.

Damage pictures from Columbia county.

         


Columbia/Sauk County tornado - spun up 3.0 miles east of Wisconsin Dells at 654 pm. It moved southeast to a point 1.0 miles southwest of Dekorra, where it ended about 740 pm.  It moved through northeast corner of Sauk County northeast of Baraboo, just south of the Wisconsin River.  Maximum damage width was about 200 yards. Path length was about 16.8 miles, with about 1.6 miles of that in Sauk County.  In Columbia County, about 20 homes were damaged, 12 barns or pole sheds/detached garages were damaged or destroyed, 6 mobile trailers were destroyed, and perhaps another 15 mobile trailers were damaged. Property damage was estimated at about $900,000 and clean-up costs about $100,000, for a total of about $1 million. In Sauk County, one home had minor roof damage due to a toppled tree, and other minor tree damage was noted along the river.



Columbia county chase photos courtesy of Doug Raflik:

         



Plot of tornadoes in Columbia and Iowa County
Plot of Tornadoes


Damage Pictures From Iowa County

     


Iowa County - brief F0 tornado on and near the Wisconsin River where State Highway 23 crosses. Only minor tree damage noted. It spun up about 653 pm and moved slowly for about 2 or 3 minutes.  It sucked water up out of the Wisconsin River. A longer-lived F0 tornado spun up 5.6 miles north-northwest of Ridgeway at 714 pm and dissipated 3.3 miles north-northeast of Ridgeway at 725 pm.  The path length was about 2.7 miles, and only minor tree damage was noted.  Another brief F0 tornado spun up about 1.5 miles west of Barneveld at 733 pm.  It damaged one home, tore up some trees, and moved some farm equipment around, before crossing State Highway 18/151 and dissipating.

Iowa county chase photos:

     






Reflectivity Loop (650kb)

Storm Relative Velociy Loop (700kb)


More meteorological discussion:

After a round of scattered morning showers and thunderstorms along with some low to mid-level clouds, the sky over western Wisconsin cleared up along and just ahead of the approaching cold front.  This allowed for daytime heating to generate sufficient atmospheric buoyancy and lift that resulted in impressive thunderstorm growth between 5 and 6 pm along the cold front.  In addition, south to southwest winds of 10 to 15 mph at the surface became westerly at 30 to 40 mph at the 18,000 foot level.  This vertical wind shear and the tendency for the stronger storms to move right of the mean storm motion resulted in rotating updrafts/supercells.  Afternoon maximum temperatures were in the 75 to 80 range with surface dewpoints in the lower to mid 60s. 

Interestingly, the sequence of events on June 6th - a morning round of showers and thunderstorms and clouds...followed by early afternoon sunshine and heating and a late afternoon/evening tornado outbreak - was very similar to the situation in two other Wisconsin tornado outbreaks.  The same sequence of event occurred on July 18, 1996 (Oakfield F5 and a total of 12 tornadoes), and August 18, 2005 (Stoughton F3 and a total of 27 tornadoes).  Of course, other factors come into play, such as vertical wind shear.


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