Thunderstorms & Tornadoes

BY: Emily Fuller & Angel Bryant

What meteorological events can cause thunderstorms?

Heating of the Earth's land surface often causes thermals, or parcels of warm air, to rise to the level of condensation. If the thermals contain sufficient moisture and the atmosphere is conditionally unstable, towering cumulus clouds may form. Under suitable conditions the cumulus towers may merge to form cumulonimbus clouds, which have an anvil-shaped top. Cumulonimbus clouds produce thunderstorms.

What atmospheric conditions favor the development of tornados?

Strong whirlwind of dust from the ground surface; appearance of a short funnel growing from the storm cloud above it. The funnel then becomes more organized and descends further from the cloud, sometimes touching the ground. (The winds forming the funnel generally move counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere, but exceptions are observed.) The funnel as a whole commonly moves forward slowly but can travel at speeds greater than 30 m (100 ft) per second.

What is the classification system used for tornadoes?

The Fujita-Pearson scale, shortened to the F-scale. The F-scale categorized a tornado by the damage inflicted on structures, then assigned a wind speed from a range of speeds thought to be associated with the type of damage. The original scale was divided into 13 categories, F-0 to F-12, indicating increasing amounts of damage. It was designed to align with the Beaufort scale of wind velocity and the Mach measure of relative speed. Only the first six categories, F0 to F5, were expected to be used, since they covered all conceivable levels of structural damage.

Where in the US do most tornadoes commonly occur and when?

Tornado Alley:  Missouri, Kansas, Tennessee, and Oklahoma, Texas, Nebraska, Colorado, and Iowa. Tornadoes are commonly spotted throughout the months of March, April, May, June.

How do tornadoes cause damage?

Enhanced Fujita Scale, also known as the EF Scale, is based on wind speed and damage. The higher the rating, the greater the damage. EF-0 is ranked causing the least damage, as EF-5 is ranked causing the most damage. EF-1 causes damage to roof shingles, and can bend flag poles, and EF-5 can do things such as uproot trees, and lift up mobile homes. 


Cotton, William R. "Thunderstorm." Grolier Multimedia Encyclopedia. Grolier Online, 2013. Web. 10 Jan. 2013.                                                                                       

Griffiths, John F. "Tornado." Grolier Multimedia Encyclopedia. Grolier Online, 2013. Web. 10 Jan. 2013.