A tornado is defined as a violently rotating column of air that is in contact with the ground. if the circulation is not on the ground, then it is defined as a funnel cloud.
Wind speeds in tornadoes can range from 65 miles per hour to 318 miles per hour, the highest tornado wind speed ever recorded. Tornadoes come in different sizes, from narrow rope-like swirls to large wedge-like funnels. In Alabama, tornadoes are often rain-wrapped and hidden or obscured by terrain. This makes them more dangerous.
Tornadoes typically develop when the right atmospheric ingredients come together, including warm, moist, unstable air near the surface; cooler, dry air aloft; and strong, atmospheric winds, increasing with height. All thunderstorms can produce tornadoes, but they are most likely to develop within supercells.
April 27th 2011
Courtesy: Huntsville NWS
In Alabama, most tornadoes occur during two peak severe weather seasons. The spring severe weather season spans March, April, and May. The fall severe weather season includes November and early December. Tornadoes typically develop during the warmest part of the day, but are possible any hour of the day or night, and during any month of the year.
What to do when you hear a tornado siren?
If you are in your home:
Go to a pre-determined shelter, such as a basement. Get under something sturdy like a heavy table, if available. Protect yourself from flying debris with pillows, heavy coats, blankets, or quilts. Use bicycle or motorcycle helmets to protect your head. If an underground shelter is not available, go to a small interior room, such as a closet, bathroom, or interior hallway, on the lowest level. Put as many walls between you and the outside as possible. Stay away from windows and doors.
If you are in a mobile home:
Leave well in advance of approaching severe weather and go to a strong building. If there is not one nearby, take shelter in the most interior room that has no windows, such as a interior bathroom or closet.
If you are caught in your vehicle or outside:
Get out and into a sturdy shelter. If one is not available nearby, get to a low spot and cover your head from flying debris. Do not take cover under an overpass as this does not provide adequate shelter during a tornado and can actually cause increased wind speeds due to a tunneling effect.
If you are in a public building, such as a hospital, school, mall, etc:
Go to the best available, pre-designated, protective area. Basements are best, but interior locations on the lowest level also offer protection. Stay away from windows and rooms with expansive roofs.