AccuWeather: How rare were the April 3 Dallas tornadoes?

By Meghan Evans Meteorologist

STATE COLLEGE, Pa. — meteorologists watched with dismay as two tornadoes developed on the ground simultaneously, one hitting the highly-populated Fort Worth, Texas, area and the other hitting the Dallas area.

I have never seen two tornadoes hit two large metropolitan areas at the same time before,” Expert Senior Meteorologist Henry Margusity said, based on his 29 years of forecasting experience.

While it is quite rare for tornadoes to hit two major metropolitan areas at the same time, people have been asking: how rare is it for a tornado to hit Dallas?

Simply put, it is rather rare for tornadoes to hit cities, since cities cover such a small area of the country. However, the number of times twisters have touched down in Dallas and Tarrant counties may be surprising.

According to the National Weather Service: “Over the last 60 years (since 1952), a total of 172 tornadoes have been reported in either Tarrant or Dallas counties, Texas. Of these, 42 have been rated at least an EF2 (wind speeds over 110 mph). The strongest, rated EF4, hit Dallas on April 25, 1994, killing three people and injuring 48. Neither county has ever reported an EF5-rated tornado. There have been five killer tornadoes that have claimed 17 lives over the past 60 years in these two counties.”

April is the most likely month for a tornado strike in Dallas, and May is the second-most likely month.

Most likely cities in the U.S. to get hit by tornadoes

Based on historical records, Dallas is not the most likely city to get hit by tornadoes in the U.S., but it is high on the list.

The most likely place to get hit by a tornado, based on the historical records of major cities, is probably Oklahoma City,” according to Harold Brooks, research meteorologist at NOAA’s National Severe Storms Laboratory in Norman, Okla. “That’s near the center location of the most likely place to have tornadoes to occur.

There’s a long history of tornadoes occurring in the metropolitan area,” Brooks added. “You need to look at some other places that are probably relatively close to that: Kansas City, Dallas, perhaps going east toward Jackson and Birmingham, Miss., are probably relatively close to those records.”

The region of the country referred to as “Tornado Alley” extends from Texas through the Plains, where tornadoes most frequently develop in the U.S. This is because dry air sweeps eastward from the Rockies, while deep moisture surges out of the Gulf of Mexico. The clashing of air masses becomes the battleground for severe weather.

A secondary zone noted for frequent tornado touchdowns is “Dixie Alley,” which stretches from the Gulf States to the Ohio Valley. The proximity to the Gulf of Mexico and, thus, the ability to tap into Gulf moisture, helps severe thunderstorms breed in “Dixie Alley.”

If we look historically, probably the city that has the biggest track record of having major tornadoes is St. Louis,” Brooks said. “The 1896 tornado, the 1927 tornadoes are adjusted for wealth of the country, are the two most damaging tornadoes in U.S. history. And then after that there’s still three other violent tornadoes in 1959 and in 1967 and then in 2011. So, St. Louis has the longest history of having those tornadoes, even though they don’t have perhaps as great of a chance of happening.”

Posted April 5, 2012

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