Alabama's tornado-free April 2012

Average tornadoes from Mar-May in Alabama. 2011 greatly skews the most recent 20-year average.

Last week, chatter began to arise about the fact that Alabama was in the midst of a tornado-free April. Well, it’s official now.

Compared to the 109 tornadoes in 2011, any number for this April would likely have seemed low, but zero?! Unheard of? No, not quite. We noted last week that the “[l]ast time was 2004. It’s happened 11 times since 1950 (thru 2011).”

So, a bit less than 20% of all years since modern records began in 1950 have featured no verified April tornadoes in Alabama. Perhaps partly why, while facing an impressive number of extreme tornadoes and major tornado outbreaks, it is not often considered part of the classic Tornado Alley.

Even discounting the absurd amount of tornadoes in 2011, April can bring Alabama quite a number of them. It’s in the heart of the spring peak of the season for the state, which is more year-round than many locations in the U.S.

The 1991-2010 average for Alabama tornadoes in April is 8.6. With that as a reference, 2011 was 12.6x the “normal.” A longer-term (1950-2011) average comes out to 6.6. However, it’s likely the early period in particular featured under-measurement of tornado activity.

Nonetheless, despite three occurrences of zero tornadoes between 2000 and 2012, recent Aprils at least appear to have been more active than in predecessor decades. Of the top-12 years for April tornadoes in Alabama since 1950, eight of them have happened since (and including) 2000.

Briefly back to the “Tornado Alley” issue (also slightly touched upon here) and why Alabama is often left out: Oklahoma, which sees its tornado numbers peak in May compared to Alabama in April, has witnessed only one May without a tornado since 1950.

Oklahoma averages 27.6 tornadoes in May. Considerably higher than Alabama at peak season. But the year with the most — 90 tornadoes in May 2010 — still produced fewer than seen in Alabama during April 2011. It was a crazy April for sure.

As we’ll see in May analyses to come, Alabama quickly falls out of the top states impacted by tornadoes as we head through the month, and the rest of the warm season, before rising toward a secondary peak in November.

In that light, we must remember that a number of tornadoes impacted the state prior to April, and that a monthly snapshot only tells part of a tale for the season.

Note: Mississippi also finished April 2012 with zero tornadoes.