The Enhanced Fujita Scale is used to assign tornadoes a rating based on estimated wind speeds and damage.
The EF Scale became operational on Feb. 1, 2007. It was revised from the original Fujita Scale, developed in 1971 by Tetsuya Fujita, to better reflect wind speed with damage observed in tornado surveys.
Deadly Severe Weather Facts & Safety Tips:
While lulls in tropical activity in the Atlantic will continue, a rapid end to the hurricane season in September does not always occur during an El Nino.
After heat has dominated headlines this summer, cool air has finally taken control of the northern half of Europe with no signs of departing anytime soon.
Steering winds could take Ignacio, as a remnant storm, into the southeastern arm of Alaska or British Columbia during the middle days of next week.
While Tropical Storm Kevin will stay well away from Mexico, its moisture will still lead to an increase in showers and thunderstorms from Baja California to the Four Corners region of the United States.
A stormy weather pattern will prevail through September across much of southern South America.
Downpours will spread from Italy to Ukraine to start the weekend before cooler air works southward and eventually sweeps the heat wave away from the Balkan Peninsula.
Washington, DC (1939)
"Once in a hundred-year rainstorm" 4.40 inches in 2 hours at the Washington Zoo.
Minneapolis, MN (1941)
Tornado - 5 dead - $450,000 damage.
Greatest natural disaster for Arizona. Rains in central Arizona caused rivers to rise 5-10 feet per hour, sweeping cars and buildings 30-40 feet downstream. Twenty-three lives were claimed by the floodwaters. This rain came from Tropical Storm Norma.