Although we are approaching the start of May, which is the peak month for thunderstorm development, the 2014 thunderstorm season has been off to a historically slow start. One advantage to this inactivity is that the insurance industry benefits from low thunderstorm losses not seen since 2004. In fact, the insurance industry has reported only $780 million of wind and thunderstorm event losses over three events (with two events yet to be estimated), according to Property Claims Service (PCS). This is far below the $4.6 billion in wind and thunderstorm event losses that have occurred on average over the last 10 years.
Not including the tornadoes that have occurred over the last few days as designated in PCS Event #40, the Storm Prediction Center has recorded 109 tornadoes as of April 24 for the 2014 calendar year which, according to BMS’ in-house tornado database from the Storm Prediction Center, indicates that this year is the slowest start to a tornado season in the 62 years of recorded data. Although the recent outbreak of tornadoes will add to the tornado count, the official count will still be in record-low territory. Harold Brooks at the National Severe Storms Laboratory, who has examined nearly 100 years of past tornado records, states that he is “challenged” to find a year that started with less tornado activity than 2014. Of the nearly 100 tornadoes reported this year, only 20 of them had been rated EF1 or higher, with the first EF3 or higher rated tornadoes only recently being recorded with this latest outbreak. This breaks a streak of 159 days, which currently stands as the fourth-longest streak on record between major tornadoes.
Despite the massive tornado that carved a swath of damage across Moore, OK during the 2013 tornado season, overall tornado statistics show that the U.S. has been in a tornado drought since the second half of 2012, with a record low number of tornadoes in 2013. Part of the explanation for the drought in intense tornadoes that has occurred since October 2013 is the persistent dip in the jet stream over the eastern half of the nation. This has unlocked the floodgates for arctic air, essentially shutting down the instability that is needed to develop explosive thunderstorms, which are often fueled by heat and moisture from the Gulf of Mexico.
The long-term forecast suggests much of the same cold will continue across the North Central Plains into the East Coast through the start of May, which should aid in putting a lid on thunderstorm development. But an extremely quiet start to the tornado season guarantees nothing about its future course, since May and June, which average 116 and 60 tornadoes, respectively (based on records from 2003 – 2013 of EF1-rated tornadoes or greater), are usually the two busiest tornado months of the year in the U.S. Despite the historically slow start, when looking at the tornado data recorded since 1953, 37 of the 62 years, or 59%, have started with below-average tornado counts of EF1 or greater. Of the 37 years that started below average, 6 years, or 16%, ended up having an above-average tornado season, The most recent years with slow starts but above-average tornado activity are 2010 and 2004, which resulted in $12.7 billion and $3.5 billion, respectively, in wind and thunderstorm event losses, according to PCS. As we saw with the recent PCS #40 declaration, there will be tornado outbreaks that cause billions of dollars in damages, but a major year like 2011 or 2008 could almost be ruled out and this recent trend should make one rethink the claims of the “new normal” back in 2011.