Lilapsophobics Beware: Tornado Maximum Is Here


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Tornado probability in the US by month. Courtesy of NOAA

Tornado probability in the US by month. Courtesy of NOAA

Lilapsophobia: Fear of tornadoes or hurricanes. The fear is justified, especially for tornadoes, in which winds can exceed three hundred miles per hour, destroying everything in their paths.

More Tornadoes In The American Midwest And Plains Than Anywhere Else

The United States’ heartland is the most tornado-prone area in the world. It’s not an accident. The conditions that lead to the highest probability of tornado formation occur east of the Rocky mountains, with the exact location of maximum frequency changing with the seasons.

When warm, humid air streams north at the surface from the Gulf of Mexico, the stage is set and one actor is in position; the second actor is a dry west wind at jet stream level. When dry air lies on top of humid air, conditional instability is the result. When the curtain rises on conditional instability, the lifting of a column of air will result in violent up and downdrafts. If the vertical wind shear (change of wind direction with height) is appropriate, rotating cells can form and become tornadoes.

Tornado Frequency In US Peaks The Second Week Of June

Daytime solar heating of the ground can also cause updrafts that can lead to tornadoes, so it is not surprising that tornado activity peaks in the middle of June, close to the solstice. However, tornado frequency varies with the season — not only in the number of tornadoes but also their location.

Overall, more tornadoes affect Texas than any other state. But this is rather misleading, as statistics often are. A better measure of tornado frequency is the number of tornadoes per unit of area. By this metric, Kansas and Florida lead the pack, and Texas is an also-ran. But here again, the numbers mislead: Florida tornadoes are normally minimal — EF0 on the Enhanced Fujita scale with top wind gusts of 85 miles per hour — while those in Kansas are often more powerful, even up to EF5 (wind gusts at least 200 miles per hour).

Finally, even this doesn’t tell the whole story. Kansas leads in tornadoes overall, but the location with the highest probability of a tornado is in northeast Colorado. Colorado rates low in terms of statewide frequency because the western part of the state rarely gets any tornadoes.

Number of tornadoes thus far in 2014 compared to average. Graph courtesy of NOAA

Number of tornadoes thus far in 2014 compared to average. Graph courtesy of NOAA

Tornado Distribution By Season

Tornado frequency generally follows the extent to which the humid air is able to move north.

  • Winter: Tornadoes are generally confined to the southern states from Texas to Georgia.
  • Spring: Activity shifts north to the central plains, midwest, and Carolinas.
  • Summer: Tornadoes occur most commonly in the northern plains, upper midwest, and mid-Atlantic states.
  • Fall: Activity retreats to the Gulf and south Atlantic coasts.

Tornado Numbers For 2014

Despite the recent outbreaks Aardvark, Beaver, and Cougar, 2014 is well below normal in the number of tornadoes reported. The winter saw almost no tornadoes, as the polar vortex kept sending cold air masses very far south, containing the warm air in the Gulf of Mexico. This same kind of pattern — an exuberant jet stream displaced to the south of its normal position, but only as far as the middle of the country — is favorable for more tornado outbreaks, and 2014 may yet prove to be a high-tornado-frequency year.

Surviving A Tornado

The best place to be during a tornado is in an underground safe room, preferably not near anything that could fall on the door and block your egress once the storm is over. However, safe rooms can be built in the basement or even on ground level in a home. Safe rooms have saved lives when tornadoes have struck in recent years.

Lilapsophobics are justified in their fear of tornadoes, but adequate preparation could save them if what they fear becomes a reality.

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