The violent tornado that struck Tuscaloosa, Alabama, on April 27, 2011, has been given a preliminary designation of at least EF4, and possibly EF5 by the National Weather Service, with funnel wind speeds of at least 165 mph (265kph), although other sources place the wind speeds well above 200 mph (322 kph). The damage path is estimated at approximately 80 miles (129km) long and 1.5 miles (2.4km) across at its widest point. The tornado, which moved through at 55 mph (88kph), was produced by a supercell thunderstorm that began in Newton County, Mississippi, and dissipated in Macon County, North Carolina.
The death toll from all the tornadoes that ripped through Arkansas, Mississippi, Alabama, Tennessee, Georgia, North Carolina, and Virginia from April 25 through April 28 exceeds 350, with hundreds more reported missing. More than 10,000 homes are reported destroyed, leaving thousands of people homeless. Federal and State emergency services are moving to find shelter for those in need while homes are being rebuilt. Rebuilding costs could exceed US$10 billion, according to one estimate.
EF refers to the Enhanced Fujita Scale, a method of rating tornado strength. According to this scale, an EF4 tornado will have wind speeds of between 207 and 260 mph (333-418kph). Damage to structures in the tornado path will be severe. Houses will be leveled or blown away, cars thrown, debris missiles flying at high speeds, and high rise structures toppled. Actually, the 165 mph funnel speed reported by the National Weather Service for the Tuscaloosa tornado indicates an EF3, rather than an EF4, but it has been reported as an EF4, possibly based on severity of the damage.
This 2011 series of tornadoes is the second most destructive in U.S. history, in terms of lives lost. The deadliest U.S. tornado occurred in March, 1925. Called the Tri-State tornado, this storm carved a 200-mile (322km) path of death and destruction across Missouri, Illinois, and Indiana, taking over 700 lives. The annual average number of tornadoes in the U.S. over the past three years was 1,376. The preliminary count in 2011 as of April 30 is 1,013, with several months left in the tornado season.
Meteorologists now have ways of measuring the energy within a storm system and can predict the high probability of a tornado and the probable area affected. Based on this information, the National Weather Service can issue tornado watches and warnings, but they still cannot predict exactly when and where the tornado will hit. It is up to those in the general warning area to take the necessary precautions. In Tuscaloosa many people did take the right protective steps, but the tornado was so powerful, it took the lives of some who had taken refuge in places that would ordinarily be considered safe.
Tornadoes are spawned when warm, moist air from the Gulf of Mexico flows north in early spring into the Midwestern and Southeastern United States. This blanket of warm, humid air rises and mingles with layers of cooler air coming in from Canada or the Pacific Ocean. The rising warm air condenses when it meets the cool air if enough moisture is present, and cumulus clouds are formed. The rising convection currents tend to create energy and instability within the cumulus formation. In some cases, the energy moves vertically down from the base of the cumuliform cloud to the ground in the form of a spinning vortex or funnel cloud. Exactly why some cumuliform clouds become rain, hail, or thunderstorms, and others become tornadoes seems to depend on the amount of energy developed within the cloud. When the energy level inside a cloud reaches a certain point and a strong rotating updraft (mesocyclone) develops, the storm formation is called a supercell. It is from supercells that violent tornadoes are produced.
Although the National Weather Service can issue tornado warnings for general areas, there is no way to predict the final path of the funnel cloud, and therefore it is hard for people living the area to move out of the tornado’s path ahead of time. In some cases, it is possible to judge the tornado’s path by watching it move once it appears on the horizon. But tornadoes can travel at up to 70 mph (112kph), so moving clear in the few minutes available is often not possible. The best thing to do for most people is to move quickly into a previously prepared safe and secure place. Basements and cellars, and prefrably under a sturdy piece of furniture such as a work bench, are considered best. If a house does not have a cellar or basement, it is recommended that you move to a small room in the middle of the house such as a closet or bathroom.
Churches and other local organizations were the first to respond with aid to people who lost their homes. The American Red Cross and other disaster relief organizations are accepting donations to special tornado relief funds to provide long-term food and shelter to those in need until the insurance companies pay claims and state and federal emergency aid comes through. Many millions throughout the United States and the world share the pain of those who suffered losses in these storms. It is fervently hoped that healing comes in time, and that people are back in their rebuilt homes and life returns to normal soon.
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