National Weather Service United States Department of Commerce

 

Location: East side of Madison

Date: 10/7/17

Rating: EF-0

Estimated Peak Wind Speed: 70-80 mph

Path Length: 4.2 miles

Path Width: 50-100 yards

Start Time: 4:59 PM CDT

End Time: 5:06 PM CDT

Fatalities: 0

Injuries: 0

 

Tornadoes in Wisconsin in October aren't common, but not unprecedented.  Late Saturday (October 7, 2017) afternoon, a line of showers developed along a frontal boundary pushing northeast through southern Wisconsin.  See the surface weather analysis map below (click to enlarge)

These showers weren't big/tall enough to produce lightning, but there was enough shear (changing wind directions and wind speeds) and instability, coupled with a very moist atmosphere, to cause many of the showers to rotate.  The shower that moved through the east side of Madison was strong enough to produce a tornado along East Washington Ave, tracking northeast to the Interstate 39/90.

This is preliminary and subject to change once the area is surveyed. 

 

Below are a series of radar images (4 panel) that begin at around 4:58 pm and end around 5:12 pm in the Sun Prairie area.  The top left quadrant is reflectivity, top right is velocity, bottom left is reflectivity and bottom right is Correlation Coefficient (CC).  CC is is a dual-pol product that allows us to see if debris is being lofted into the storm from a tornado.  You'll see at around 5:02 there is a good CC signature of the debris (mostly leaves).  

Tornado genesis around 4:58 PM (click to enlarge):

At 5:02 PM:

At 5:06 PM:

At 5:11 PM:

All of this information is preliminary and subject to change as our survey crew assesses the damage, path, strength and timing.

We have received reports of several trees down, some trees on homes, and damage to a few businesses. 

The pictures below are from John Marion and provided to us by Milwaukee SKYWARN:

 

 
 

 

 

Pictures below are from our NWS Storm Survey

 

 

 

 

Below are pictures of thunderstorm wind damage in Pardeeville from storm spotter David Casper:

 

 


Davis