March 2013 Tornadoes: Fewest in Decades

The persistent, stubborn March cold in the Plains, South and East has had at least one benefit.  

March 2013 is poised to be one of the least tornadic Marches in the U.S. in decades.

In preliminary data through March 31, only 16 tornadoes have been tallied across the nation in March 2013, according to Severe Weather Expert, Dr. Greg Forbes (Facebook | Twitter).

If this preliminary total holds up, this would be thelowest March U.S. tornado count in 35 years, since only 17 tornadoes were counted in March 1978.  The last March with a lower U.S. tornado tally was 1969, with only 8 U.S. tornadoes. 

March 2012 couldn't have been more different, nearly doubling the monthly average with 154 tornadoes, punctuated by the Mar. 2-3 outbreak, heavily damaging the towns of W. Liberty, Ky.and Henryville, Ind., among others.

(MORE:  Mar. 2-3, 2012 outbreak recap) 

This low count in March 2013 is particularly impressive given today's technology, such as Doppler radar, smartphones and social media, as well as a more expansive spotter network. 

Weak tornadoes are much less likely to go undetected today compared to past years. This contributes to rising tornado counts compared to past decades, a concept called "tornado inflation".

Incidentally, a quiet March often doesn't portend a quiet April or May.

Only 75 March tornadoes, slightly below the 10-year average of 98 tornadoes, touched down in March 2011.  Then, all hell broke loose in April 2011, with a monthly record 758 U.S. tornadoes.

Why the "tornadic break" in March 2013?  The answer lies in the dominant jet stream pattern.

Put simply, the jet stream has most often featured a prominent dip, or trough, in the East and a general northward bend, or ridge, in the West.  For severe weather outbreaks this time of year, you need the opposite:  a jet stream trough swinging out of the West into the Plains and South.

Near the surface, reinforcing cold fronts into the Midwest and South have kept warm and humid air from establishing itself and/or moving too far north in the few cases when a jet stream disturbance has managed to push into the Midwest and South.