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Unformatted text preview: Tornado Climatology Basics Tornadoes have occurred in every state but are more frequent in the plains/Mississippi Valley Tornadoes most frequent in afternoon (3-7 pm) Tornadoes can occur every month of the year in the USA but More than 50% of annual occurrences are in April, May and June here in the USA About 75% of annual occurrences are March through July May tends to have the greatest number of tornadoes here in the USA with an average of 5 a day April tends to have the strongest or violent tornadoes Average tornado movement SW to the NE Average tornado forward speed is 30 mph Toward the end of their lifetime, some tornadoes make abrupt right/left turns On average here in the US, there are about 1300 tornadoes a year On average, of those 1300 o 80% are weak (wind < 110 mph) o 19% are strong (wind 110-200 mph) o 1% are violent (wind > 200 mph) The Worst Tornado Outbreaks in US History April 3-4 1974 (WORST) 16 hour period (began at 9:30 AM April 3, ended predawn April 4) Tornado Development...
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- Spring '08