UPDATE: Severe Weather's Coming to Ames Sooner or Later. Do You Know What to Do?

People might have ignored today's tornado warning siren, but it's nothing to dismiss.

Tornadoes have already killed 55 people so far this year in the United States.

Most Iowans know that a tornado is a rapidly rotating column of air in contact with the ground. But recognizing one isn't so easy. A visible cloud is not always seen.

Some tornadoes may not appear to extend to the ground but still cause considerable damage, and others may be obscured by rain.

Tornadoes can take on various shapes and sizes, and most produce winds less than 120 mph, but a few are capable of producing winds more than 200 mph.

Predicting what a tornado is going to do is difficult as some tornadoes are very small and last for only a minute or so, while others can be a mile wide or larger and stay on the ground for more than an hour.

In 2011 Iowa saw a total of 50 tornadoes. Of these tornadoes, 20 were rated EF0; 19 were rated EF1; 7 were rated EF2; 3 were rated EF3 and 1 was rated EF4 in Pocahontas County on April 9. In Iowa, 16 people were injured by tornadoes, but luckily no deaths were reported. For some interesting information on the frequency of tornadoes in Iowa, see the climate section of the National Weather Service website at www.weather.gov/desmoines.

Read on to learn the different between a watch and a warning and what to do in the event of a tornado. 

The National Weather Service, in conjunction with area police and fire departments, are testing your weather mettle this week with a statewide tornado drill on Wednesday at 10 a.m.

The drill will proceed as follows:

10:00 a.m.: Tornado watch (drill) given over NOAA Weather Radio. 
 
10:15 a.m.: Tornado warning (drill) given over NOAA Weather Radio and outdoor warning siren activation.
 
10:30 a.m.: End of drill.

In the event of an actual severe weather emergency, the drill will be postponed until 10 a.m. Thursday, April 5.

Can't remember the difference between a watch and a warning? Thanks to the National Weather Service, we have you covered:

Watch: A National Weather Service product indicating that a particular hazard is possible, i.e., that conditions are more favorable than usual for its occurrence. A watch is a recommendation for planning, preparation, and increased awareness (i.e., to be alert for changing weather, listen for further information, and think about what to do if the danger materializes).

Warning: A product issued by National Weather Service local offices indicating that a particular weather hazard is either imminent or has been reported. A warning indicates the need to take action to protect life and property. The type of hazard is reflected in the type of warning (i.e., tornado warning, blizzard warning, etc.).

Don't know what to do in the event of severe weather? Here's the skinny on tornado safety:

In a house with a basement: Avoid windows. Get in the basement and under some kind of sturdy protection (heavy table or work bench), or cover yourself with a mattress or sleeping bag. Know where very heavy objects rest on the floor above (pianos, refrigerators, waterbeds, etc.) and do not go under them. They may fall down through a weakened floor and crush you. Head protection, such as a helmet, can offer some protection also.

In a house with no basement, a dorm, or an apartment: Avoid windows. Go to the lowest floor, small center room (like a bathroom or closet), under a stairwell, or in an interior hallway with no windows. Crouch as low as possible to the floor, facing down; and cover your head with your hands. A bath tub may offer a shell of partial protection. Even in an interior room, you should cover yourself with some sort of thick padding (mattress, blankets, etc.), to protect against falling debris in case the roof and ceiling fail. A helmet can offer some protection against head injury.

In an office building, hospital, nursing home or skyscraper: Go directly to an enclosed, windowless area in the center of the building -- away from glass and on the lowest floor possible. Then, crouch down and cover your head. Interior stairwells are usually good places to take shelter, and if not crowded, allow you to get to a lower level quickly. Stay off the elevators; you could be trapped in them if the power is lost.

In a mobile home: Get out! Even if your home is tied down, it is not as safe as an underground shelter or permanent, sturdy building. Go to one of those shelters, or to a nearby permanent structure, using your tornado evacuation plan. Most tornadoes can destroy even tied-down mobile homes; and it is best not to play the low odds that yours will make it. This mobile-home safety video from the State of Missouri may be useful in developing your plan.

At school: Follow the drill! Go to the interior hall or room in an orderly way as you are told. Crouch low, head down, and protect the back of your head with your arms. Stay away from windows and large open rooms like gyms and auditoriums.

In a car or truck: Vehicles are extremely risky in a tornado. There is no safe option when caught in a tornado in a car, just slightly less-dangerous ones. If the tornado is visible, far away, and the traffic is light, you may be able to drive out of its path by moving at right angles to the tornado. Seek shelter in a sturdy building, or runderground if possible. If you are caught by extreme winds or flying debris, park the car as quickly and safely as possible -- out of the traffic lanes. Stay in the car with the seat belt on. Put your head down below the windows; cover your head with your hands and a blanket, coat, or other cushion if possible. If you can safely get noticeably lower than the level of the roadway,leave your car and lie in that area, covering your head with your hands. Avoid seeking shelter under bridges, which can create deadly traffic hazards while offering little protection against flying debris.

In the open outdoors: If possible, seek shelter in a sturdy building. If not, lie flat and face-down on low ground, protecting the back of your head with your arms. Get as far away from trees and cars as you can; they may be blown onto you in a tornado.

In a shopping mall or large store: Do not panic. Watch for others. Move as quickly as possible to an interior bathroom, storage room or other small enclosed area, away from windows.

In a church or theater: Do not panic. If possible, move quickly but orderly to an interior bathroom or hallway, away from windows. Crouch face-down and protect your head with your arms. If there is no time to do that, get under the seats or pews, protecting your head with your arms or hands.