Understanding Tornadoes

a cumulonimbus cloud

So what exactly is a tornado? A tornado is "a violently rotating column of air, pendant from a cumulonimbus cloud and nearly always visible as a "funnel" cloud." On a local scale, a tornado is the most destructive of atmospheric phenomenon.

A tornado has five stages that it will undergo during its life cycle:

  1. A rotating column of air will form within a cumulonimbus cloud and extend toward the ground. This can be seen as a rotating funnel that dropping out of the bottom of the cloud towards the ground. Until the rotating funnel reaches the ground, it is called a "funnel cloud."
  2. When the rotating column of air reaches the ground, it is now called a "tornado." The funnel can be seen touching the ground, and sometimes dust and debris can be seen swirling about on the ground before the tornado actually touches down.
  3. Once the tornado reaches "maturity," it is almost always vertical and touching the ground. At this point, anything the tornado encounters is severely damaged or destroyed.
  4. During the "shrinking stage," the funnel will become narrow and less vertical. In this stage, the damage path becomes smaller.
  5. When a tornado reaches the "decaying stage," the funnel is stretched into a rope shape. The visible portion becomes contorted and finally dissipates. This stage is also called the "rope stage."

The severity of a tornado is ranked by the following Fujita Scale:

Category Sustained Winds Damage
F-0 40 - 72 mph Chimney damage, tree branches broken
F-1 73 - 112 mph Mobile homes pushed off their foundations or overturned
F-2 113 - 157 mph Considerable damage. Mobile homes demolished. Trees uprooted
F-3 158 - 205 mph Roofs and walls torn down. Trains overturned. Cars thrown.
F-4 206 - 260 mph Well constructed walls leveled
F-5 261 - 318 mph Homes lifted off foundations and carried considerable distances. Autos thrown as far as 100 meters.

Tornado Watches and Warnings


People often misunderstand the difference between a tornado watch and a tornado warning. When a tornado watch is issued it means that the atmospheric conditions are capable of producing a tornado. A tornado warning is issued when a tornado has been detected or actually spotted by someone on the ground. So, when you hear of a tornado watch being issued, you should pay close attention to weather updates and the weather conditions in your area (and plan accordingly). You should always seek proper shelter when a tornado warning is issued for your area.

Also, you'll notice that watches are usually issued across very broad areas. Warnings are usually localized in a single county or a cluster of neighboring counties.

Surviving a Tornado

Knowing what to do during a tornado and having a plan of action is key to your survival. However, you should note that your plan will vary according to your surrounding and the availability of a proper shelter.

Houses (with foundations)

You and your family should have a room or area within your home designated as a tornado shelter. A basement will offer the most protection. If your home does not have a basement, a bathroom or closet on the bottom floor of your home is the best place to go. If possible, choose a bathroom or closet that is located towards the center of your home. Place a cushion of some sort over you and your family for extra protection.

Mobile Homes
mobile home destroyed Mobile Homes offer terrible protection from tornadoes. Straps or any other sort tie-downs are no match for the extremely high winds associated with tornadoes. If you live in a mobile home, your plan should include leaving your mobile home to seek shelter elsewhere. Many mobile home communities offer recreational buildings or laundry rooms that can serve as a more suitable shelter. As a last resort, lie down in a ditch or low spot in the land. Yes, being in a ditch is safer that staying in a mobile home.

The high winds associated with a tornado can toss even the biggest truck like a tin can. Therefore, do not seek shelter in an automobile. Also, do not try to out-run a tornado. Go inside a nearby sturdy building or, as a last result, lie down in a ditch or other low spot in the ground.

Videos seen on television have made taking shelter beneath an overpass a popular thing to do during a tornado. You should know that overpasses are not an ideal shelter and can actually increase the probability that you will be injured. This is because the already excessive winds can be further accelerated beneath the overpass.

Hotels, Shopping Centers, and Office Buildings
Take shelter in an interior hallway on a lower floor. A closet, bathroom, or other small room with short, stout walls will offer some protection from collapse and flying debris. Otherwise, get under a piece of heavy furniture and stay away from windows. Many tornado deaths are due to the collapse of a wide spanning walls. A corner area, away from windows, is more safe than the middle of a wide spanned wall.

Out in Open Land
When you see severe weather approaching, you should seek inside shelter immediately. If no shelter is available, lie down in a ditch or depression in the ground and cover your head and neck. Be aware that you are also exposed to falling trees/limbs, lightning, and flash floods.

All public schools have reliable ways to monitor tornado watches and warnings, and each school has a designated emergency plan that will lead pupils and faculty to designated safe areas. Teachers should lead students out of gyms, auditoriums and portable classrooms to interior rooms and hallways on ground level floors. Students should stay away from glass, both in windows and doors. They should crouch down and seek shelter under a classroom desk, if possible. Otherwise, they should make themselves as small as possible, being sure to cover the head.

Theaters, Auditoriums, and Warehouses
Move into a small interior room such as a closet or bathroom. Otherwise, you should evacuate the building and search for more suitable shelter, if time allows.