Wisconsin Tornado and Severe Weather Awareness

Severe Thunderstorms

At any given moment, there are thousands of thunderstorms occurring worldwide.  Most of these storms are beneficial, bringing needed rainfall.  A small percentage of the storms become severe.  Although the area stretching from Texas to Minnesota has the greatest known occurrences of U.S. severe thunderstorms, no place in the U.S. is immune to the threat of severe weather. 

Although severe thunderstorms can be fairly small, averaging around 10 to 15 miles in diameter, and have an average lifetime of 20 to 30 minutes, they can cause a tremendous amount of damage.  Some supercell thunderstorms can have a lifespan of several hours. 

Severe thunderstorms are defined as having one or more of the following:

  • Wind gusts of 58 mph or higher
  • Hail of 1 inch or greater
  • Tornado
  • Flash Flood

Severe thunderstorms also typically contain dangerous cloud to ground lightning.

WISCONSIN SEES AN AVERAGE OF 30 TO 40 DAYS A YEAR WITH THUNDERSTORMS.
HERE/S THE BREAKDOWN ON SHORT-LIVED SEVERE WEATHER EVENTS IN
WISCONSIN...FOR THE PERIOD OF 1982-2009
***54 PERCENT OF ALL SEVERE EVENTS IN THE STATE ARE
      STRAIGHT LINE WIND EVENTS /WIND SPEEDS 58 MPH OR HIGHER/

   ***34 PERCENT ARE HAIL EVENTS WITH HAIL-STONES THAT ARE AT
      LEAST 1 INCH IN DIAMETER

   ***6 PERCENT ARE TORNADO EVENTS

   ***6 PERCENT ARE FLASH FLOODS.

HERE ARE SOME MORE INTERESTING FACTS ABOUT SEVERE THUNDERSTORMS IN
THE STATE OF WISCONSIN...

...HAIL CAN OCCUR IN ANY COUNTY HOWEVER THE SOUTHERN HALF OF
   WISCONSIN HAS A GREATER NUMBER OF RECORDED HAIL EVENTS.

...EACH SUMMER THERE ARE ABOUT 15 SEVERE THUNDERSTORMS IN WISCONSIN
   WHICH PRODUCE HAIL 1.5 INCHES IN DIAMETER OR LARGER.

...SEVERE THUNDERSTORMS CAN OCCUR AT ANY TIME OF THE DAY AND AT ANY
   TIME OF THE YEAR.  THE PEAK SEASON FOR SEVERE THUNDERSTORMS IS
   BETWEEN APRIL AND AUGUST AND MOST LIKELY TO OCCUR IN THE LATE
   AFTERNOON OR EVENING HOURS.

...ON SUNDAY, MAY 31, 1998, HURRICANE-FORCE WINDS IN EXCESS OF 100 MPH
   RAKED SEVERAL COUNTIES IN SOUTH CENTRAL AND SOUTHEAST WISCONSIN.
   A PEAK GUST OF 128 MPH WAS MEASURED IN SOUTHERN DODGE COUNTY. ONE
   PERSON IN SOUTHERN WASHINGTON COUNTY WAS CRUSHED TO DEATH WHILE
   SLEEPING DURING THE POWERFUL STORM WHEN A TREE FELL ON THEIR 
   HOME.  HURRICANE WINDS START AT 74 MPH. 

...FROM 1970 TO 2012...WISCONSIN HAS HAD 25 DAYS WITH DOCUMENTED
   STRAIGHT-LINE THUNDERSTORM DOWN-BURST WINDS OF 100 MPH OR HIGHER.

...ON JULY 4TH, 1977...A POWERFUL THUNDERSTORM SYSTEM GENERATED 
   WIND GUSTS OF OVER 100...WITH SOME GUSTS ESTIMATED AS HIGH AS 150
   TO 155 MPH OVER NORTHERN WISCONSIN. SEVERE TREE DAMAGE OCCURRED 
   OVER A DISTANCE OF 166 MILES. 

...SEVERE THUNDERSTORM WATCH AND WARNINGS...
IT IS IMPORTANT TO KNOW THE DIFFERENCE BETWEEN A SEVERE THUNDERSTORM
WATCH AND A WARNING.  WHEN A SEVERE THUNDERSTORM WATCH IS ISSUED...IT
MEANS THAT SEVERE THUNDERSTORMS ARE POSSIBLE.  WHEN A SEVERE
THUNDERSTORM WARNING IS ISSUED...IT MEANS THAT SEVERE THUNDERSTORMS
ARE IMMINENT OR OCCURRING IN YOUR AREA.

ALWAYS MAKE SURE THAT YOU KNOW THE NAME OF THE COUNTY IN WHICH YOU
RESIDE. WATCHES AND WARNINGS ARE DEFINED ON A COUNTY BASIS. IF SEVERE
THUNDERSTORMS ARE A POSSIBILITY IN YOUR AREA...MONITOR A NOAA WEATHER
RADIO ALL-HAZARDS...LOCAL TV OR RADIO STATIONS FOR THE LATEST SEVERE 
THUNDERSTORM WATCHES AND WARNINGS FOR YOUR AREA.

IF A WARNING IS ISSUED YOU NEED TO TAKE ACTION TO PROTECT YOURSELF.
MOVE TO A STURDY BUILDING AND DO NOT STAND NEAR WINDOWS.  DO NOT USE
TELEPHONES UNLESS IN AN EMERGENCY UNTIL THE STORM HAS PASSED YOUR
AREA.  ALWAYS REMEMBER THAT THUNDERSTORMS CAN AND DO PRODUCE
TORNADOES WITH LITTLE OR NO ADVANCE WARNING.

FOR ADDITIONAL SEVERE WEATHER INFORMATION AND UP TO DATE FORECASTS
AND WARNINGS PLEASE VISIT OUR WEB SITE AT:

http://weather.gov/mkx

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