St. Patricks Day 2015 Sun Prairie Tornado


7 Minutes

Time It Formed

4:59 PM (CST)

Time It Dissipated

5:06 PM (CST)

Fujita Scale Rating


Maximum Winds

115 mph

Path Length

9 miles

Maximum Width

45-65 yards

Place(s) impacted

Sun Prarie, Wisconsin

Damage Caused

$1,100,000 (2014 USD)

Fatalities Caused

One (1)

The St. Patricks Day 2015 Sun Prarie Tornado was a Rare Anticyclonic EF2 tornado that caused unexpectedly impacted Sun Prarie, Wisconsin on March 17th, 2015.


Tornado 454

The Tornado at peak intensity.

it had been a quiet start to the Week for Meteorologists, barely any storms were active across the US, and those that were active, only a few barely became severe in Oregon and Washington States, but no tornadoes were reported from them.

Until About 11:45 AM on St. Patricks Day, When Local Meteorologists began to monitor a new area of Weak Severe Storms moving North-West from Chicago, Illinois.

And about half an hour or so after the storm complex formed, a weak Funnel was Reported on the Beaches of Lake Michigan. The First reported one in Three Days.

Afterwards, some of the storms weakened, with some storms staying the same and one particular cell slowly organizing and strengthening.

The Event

  • Map of the Day's Greatest Severe Risk
  • The Storm as it unexpectedly gained Severe Characteristics
  • The Storm repeatedly varied between an LP and HP Cell
  • The Set up during St. Patricks Day
  • A Gustnado spawned by the storm
  • Two and a Half Inch Hail from the Storm
  • Sirens sounded after Spotters observed Rotation on the Storm
  • The Storm from another Perspective
  • A Radar image of the Storm
  • Strong Anticyclonic Rotation (Pre-EF2)
  • The Tornado as it Formed
  • The Common Risk Area in March for Tornadoes
  • An EF0 SSE of Madison, Spawned by the same Cell
  • The Tornado as an EF1, entering Sun Prairie
  • The Tornado at its strongest (A Weak EF2)
  • Minor Damage caused by the Tornado
  • The Tornado While a Strong EF1, as seen by another chaser
  • A Trailer Destroyed by the Anticyclonic EF2
  • Another Wrecked Trailer
  • Damage caused to a house by the Tornado
  • 2 inch hail reported in Madison
  • Some flooding along the Illinois/Wisconsin border

At 3:00 PM, whilst most of the storms in the Complex had either Weakened or Dissipated, One continued North-West, barely maintaining strength and structural integrity.

And this cell briefly produced a Weak EF0 Tornado East-Southeast of Madison, Wisconsin at about 3:11 PM.

The Storm briefly weakened before Re-strengthening as it began to Enter Sun Prairie, Wisconsin at 4:00 PM, and Spotters began to report an area of Anticyclonic Rotation on the Storm.

And for the next Twenty Minutes to half hour, the storm produced intermittent funnels, before they stopped again.

Finally at just before 5:00 PM, spotters witnessed the Formation of an Anticyclonic Tornado. The was the first time since 2014 that an Anticylonic tornado had formed anywhere in the US.

The Tornado tore through small neighborhoods, causing some damage as it did, and Killing One when it caused destruction in a trailer park.


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