Tornadoes are one of the most powerful forces of nature, and are more common here in the U.S. than anywhere else in the world. You should always have a plan in place to ensure your family's safety during a tornado warning.
It's a sound many of us have heard too many times living in Iowa...outdoor warning sirens, alerting us that severe weather is barreling in.
Not every severe thunderstorm produces a tornado. The right atmospheric ingredients must be present.
Most commonly in Iowa and the Midwest, a tornado will form in a supercell thunderstorm, which is a thunderstorm with a constant rotating updraft. These develop in areas with sufficient moisture, instability lift, and important for a tornado -- shear.
Shear is the difference in wind speed and or wind direction with height.
Speed shear near the ground creates a horizontal spin in the air. Warm, moist air feeding into the storm, known as an updraft, is sometimes strong enough to lift the horizontal rotating column of air into the supercell.
If there is a drastic change in the wind direction with height, known as directional shear, the air begins to tilt vertically and rotate as rain and hail
Cooled air from the back side of the storm sinks to the ground, creating additional spin leading to a wall cloud, which is a rotating, lowering cloud from the parent storm. Eventually, that wall cloud forms a funnel cloud and when that touches the ground, it's officially a tornado.
A tornado watch means conditions are favorable for a tornado to develop. A tornado warning is issued when a tornado has been detected by Doppler Radar, or has been spotted by a trained storm spotter.
Once a tornado warning is issued, it's time to take shelter. No place outside is safe. Find the nearest indoor shelter.
Put as many walls between yourself and the outside as possible. If a basement isn't an option, an interior room such as a closet or bathroom is your best bet.
Take something to cover your head from possible flying debris. The best place to be during a tornado or severe weather is in the basement.
Make sure you know where to go whether you're at the grocery store, at school or at work. Many public places will have a designated severe weather shelter area.
In Iowa, the prime months for tornadoes are April through August. Since 1980, Iowa has averaged approximately 49 tornadoes per year, with one occurring every month except January.
Tornadoes can occur at any time of day. While most occur during the late afternoon or evening, they can occur at night and even in the wee hours of the morning.
It is nearly impossible to get an exact measurement of the winds inside a tornado, so meteorologists use the Enhanced Fujita scale to rate tornadoes. The ratings comes after the tornado, when surveyors look at the damage and estimate how strong the winds were. They range from EF-0 to EF-5. The last EF-5 tornado in Iowa was the Parkersburg-New Hartford-Dunkerton tornado on May 25, 2008.
Once a tornado warning is issued for any of the 21 counties in the KWWL viewing area, we will be first on the air on channel 7, the CW 7.2 and ME-TV 7.3, bringing you continuous updates and potentially life-saving information.