US Tornado Update–April 2013
By Paul Homewood
On average, April is expected to be the third busiest month for tornadoes in the US, the busiest months being May and June. On a YTD basis, about a quarter of all tornadoes occur by the end of April. So the tornado count from NOAA at this stage of the year gives a first real glimpse at how the annual trend is developing.
It is therefore pleasing to be able to report that, so far, tornado numbers are extremely low.
There have been 233 preliminary tornado reports up to 30th April, the lowest number in the 2005-13 period, and less than half the average of 557 for 2005-12.
On average, about 85% of preliminary reports end up being confirmed, after non tornado events and duplicates are sifted out. Of those remaining, about 40% are EF1 or stronger. (For long term climatological comparisons, EF0 tornadoes need to be excluded, because Doppler and other improvements in observation nowadays spot many of these events that would have been missed as recently as two decades ago – for more on this, check out NOAA here.)
So the projected figure for EF1+ tornadoes currently stands at about 80, which compares with the 1970-2009 average of 150. Interestingly, although last year finished as one of the quietest on record for tornadoes, at the end of April it was above average, with 241 EF1+. The low annual numbers were the result of extremely low activity in May and June.
So far this year, there have been only three tornado related deaths. There has been widespread variation in fatality numbers over the years, so perhaps averages don’t mean a great deal. Nevertheless, this year’s figure is the lowest in the 2000-13 period.
All data is from NOAA’s Storm Prediction Centre.