MILWAUKEE -- Don't be alarmed when you hear the loud wail of tornado sirens at 1:45 p.m. Thursday. It's just a test.

The annual testing is part of Tornado and Severe Weather Awareness Week in Wisconsin.

Wisconsin averages about 23 tornadoes annually. Testing allows law enforcement, businesses, residents and schools to practice their emergency plans in case a tornado hits.

The National Weather Service will issue a Mock Tornado Watch at 1 p.m.

A tornado watch means conditions are favorable for tornadoes to occur in the area where the watch has been issued. It does not mean a tornado is on the ground, but the public should be prepared in case conditions change.

A Mock Tornado Warning will be issued at 1:45 p.m.

A tornado warning means a tornado has been detected and you should quickly move to a shelter or designated place of safety.

The drill ends at 2 p.m. 

Debunking Myths

The National Weather Service cites several myths about tornadoes, including a few you may have heard in our area. Officials say don't be fooled by the following statements on tornadoes:

Myth - Lakes protect nearby areas from tornadoes.

Fact - Lake Michigan is not the Milwaukee area's secret weapon against tornadoes. The National Weather Service says cold water and cool air on top of the lake can provide a stable environment, but a thunderstorm producing a tornado moving toward a cold lake has something much larger driving it than the cold water can slow down or inhibit. 

Typical lake breezes along the Lake Michigan shore only affect a small portion of the lower atmosphere.  Warm and unstable air above this lake breeze could very well sustain a thunderstorm's strength.

For example on March 8, 2000, Milwaukee County experienced its earliest tornado on record at a time when Lake Michigan is climatologically coldest.  On August 8, 2011, a weak tornado developed on Lake Monona in Madison.  It stayed over the lake as a waterspout and did not cause damage. This weak waterspout was associated with a rain-shower and  there were no thunderstorms in the area.

Myth - Big cities and tall buildings are protected from tornadoes.

Fact - Many large cities in the U.S. have been directly hit by tornadoes in recent years, including Miami, Salt Lake City, Birmingham, Oklahoma City, Houston, Fort Worth, Nashville and Joplin, MO. 

Also, remember that tornadoes are typically 5 to 10 miles tall.  A group of buildings with individual heights of 500 to 1000 feet can not deflect or destroy a tornado.

Even the U.S. Bank Center, Milwaukee's tallest skyscraper at 601 feet, can't protect the city from a tornado. 

Myth - Seek shelter under an overpass if you are outside when a tornado strikes.

Fact - This may sound like a good idea, but the National Weather Service says it can cause more harm than good. 

Deadly flying debris can still be blasted into the spaces between bridge and grade, and impaled in any people hiding there.

Even if you hold on as tight as you can to the girders (if they exist), people may be blown out from under the bridge and into the open, possibly into the tornado itself. Chances for survival are slim. Remember the flying cow in the 1996 movie Twister?

Worse, the bridge itself could just collapse onto people underneath. The structural integrity of many bridges during a tornado is unknown--even for those which may look sturdy.