Roosevelt Severe & Unusual Weather: tornado record off to slow start

Tuesday, April 22, 2014

tornado record off to slow start

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Tornadoes by the Numbers

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Despite recent tornadoes in Missouri, Texas, Mississippi and North Carolina, among other states, we have set a new record for a lack of stronger tornadoes-to-date in 2014.

Latest first F/EF3+ tornadoes since 1950

List of previous latest first F/EF3+ tornadoes on record dating to 1950. (Data: Univ. of Alabama-Huntsville)

ENLARGE

Through April 21, not one tornado of EF3 intensity or stronger has been observed anywhere in the U.S., the latest wait for the first such tornado in any year on record dating to 1950, according to theUniversity of Alabama-Huntsville.

March 31, 2002 was the previous record latest date of the season's first F3 or EF3 tornado. The Enhanced-Fujita scale replaced the original Fujita Scale on Feb. 1, 2007.

The last U.S. tornado of EF3 intensity or stronger was during the Nov. 17, 2013 outbreak in the Midwest, making this a five-month stretch without one.

According to statistics compiled by severe weather expert, Dr. Greg Forbes (Twitter | Facebook), the period from January through March averaged between eight and nine tornadoes of F/EF3+ intensity in the period 1950-2012.

While we have had several episodes of severe thunderstorms in 2014, we've been fortunate enough to avoid the volatile combination of low-level wind shear (rapidly changing wind direction and speed with height) and strong instability (very warm and humid air near the surface topped by cold, dry air aloft) known to spawn large, destructive tornado outbreaks.

As you can see in the pie chart below, while stronger tornadoes (EF3+) are more rare, they make up a large majority of tornado fatalities each year.

Create Infographics

Average monthly U.S. tornado count from 1984-2013. Note the sharp increase from March into April.

ENLARGE GRAPH

We hope this good fortune continues. However, climatology says it will not.

April and May lead with 10-11 F/EF3+ tornadoes each month, on average, according to Dr. Forbes.

Keep in mind while current tornado counts in 2014 are roughly 71 percent below the average-to-date, destructive outbreaks do occur in years with fewer overall tornado counts.

Both 2012 and 2013 featured at least 400 fewer U.S. tornadoes than the 10-year average. Despite fewer tornadoes, destructive twisters still occurred:

Mar. 2-3, 2012: EF4 in Henryville, Ind.; EF3 in West Liberty, Ky.
May 15, 2013: EF4 in Granbury, Texas
May 19-20, 2013: EF5 in Moore, Okla.
May 31, 2013: EF3 in El Reno, Okla.
Nov, 17, 2013: EF4 in Washington, Ill.

Develop or refresh your plan in case a tornado or severe thunderstorm warning is issued for your area. Download The Weather Channel app for your smartphone or tablet, and sign up for severe weather alerts sent to you via text message or email.

(FORECAST: Severe Weather Tracker)

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Damaged cars at Sikes Senter Mall in Wichita Falls, Texas on Apr. 11, 1979. (Photo credit: Don Burgess/NSSL/Inst. for Disaster Research at Texas Tech Univ.)