The EF4 tornado that struck Fairdale, IL on April 9, 2015. An historic weather event for northern Illinois.
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A tornado is a vortex or powerful whirling wind, often visible as a funnel-shaped cloud hanging from the base of a thunderstorm. In some places such storms are referred to as cyclones.
The tornado that struck Joplin, Missouri, holds the dubious distinction as the costliest single tornado in American history, generating over $2 billion in insurance claims. The massive tornado was classified an EF-5 on the Enhanced Fujita Scale, and the devastating winds exceeded 200 mph. With approximately 160 human casualties, it is also the deadliest American tornado on record since 1947.
Unfortunately, many casualties might have been avoided. A post-tornado survey conducted by the National Weather Service revealed that most people did not heed the tornado warnings and take cover, assuming they were false alarms. The National Weather Service is working to improve the tornado warning communication process.
Thirteen of the Joplin tornado survivors were diagnosed with a deadly fungal infection known as mucormycosis. This type of infection can be contracted during natural disasters, when victims have open wounds that are contaminated with dirt and decaying vegetation.
It can be very violent and destructive as it moves across land in a fairly narrow path, usually a few hundred yards in width. Wind speeds are most often too strong to measure with instruments and are often estimated from the damages they cause. Winds have been estimated to exceed 350 miles per hour (563 kph). Very steep pressure gradients are also associated with tornados and contribute to their destructiveness. Sudden changes in atmospheric pressure taking place as the storm passes sometimes cause walls and roofs of buildings to explode or collapse.
Tornadoes most frequently occur in the United States in the central plains where maritime polar and maritime tropical air masses often meet, producing highly unstable atmospheric conditions conducive to the development of severe thunderstorms. Most tornados occur between noon and sunset, when late afternoon heating contributes to atmospheric instability.
In addition to clashes between warm and cold fronts, tornadoes are often spawned by hurricanes and tropical storms. Global warming is expected to increase sea surface temperatures in the tropical regions of the world, which will increase the amount of energy in the oceans available for such storms. The result of this process could be an increase in the annual frequency of hurricanes, and an increase in their intensity (wind speed), with a consequential increase in both the number and strength of tornadoes they create. The process of tornado formation is, however, extremely complicated, so the influence of warmer ocean temperatures could be countered by the typical factors that disrupt formation and result in no net gain in frequency.