Win tickets to see the smash hit musical Mamma Mia at the Roanoke Civic Center. Two winners will each receive four tickets!
Wednesday, August 21, 2013
After the tragic May 20 Moore, Okla., tornado, I wrote this in the Weather Journal column:
“Though sparse historical tornado records make it uncertain, it is widely believed by severe weather experts that 2012 had the fewest tornadoes nationally in the past 60 years. We can quit talking about that now.”
Well, maybe not.
Despite a series of violent tornadoes centering on the Oklahoma City metropolitan area in late May, killing 34 people over 13 days, total tornadoes in the U.S. are again extremely low relative to what is considered normal.
Through Aug. 18, there have been a mathematically estimated 609 tornadoes in the U.S. in 2013. That is figured to be near — even slightly below — the minimum number of tornadoes that occurred through the same date in all years since 1954.
The Storm Prediction Center applies a mathematical formula to offset the increase in tornado reports that have occurred from the 1950s to the modern era because of an improved spotter network, the advent of storm chasing, sprawling population, huge gains in video and photography technology, and the development of Doppler radar.
In short, more tornadoes that occur are seen, experienced or recorded after the fact than in the 1950s because there are more people in more places to see and experience those tornadoes, so modern counts will be higher even in years when severe weather is not more abundant.
There have been more than 700 reports of tornadoes so far in 2013, but almost inevitably, the actual number of tornadoes is later determined to be fewer, once duplicate accounts, mistaken reports and damage caused by non-tornadic winds are subtracted out of the count.
The mathematical formula is a way to estimate actual tornadoes from the tornado count before the final analysis of each tornado report is completed.
In an average year, there would already have been more than 1,000 tornadoes by this time on the way to an annual average of a little less than 1,300. The majority of tornadoes in the U.S. occur in the first half of a year, peaking in the April to June period.
So for the second year in a row, there have been far fewer tornadoes raking the U.S. than should be expected, after an extremely prolific and deadly 2011 season.
Generally, the reasons for 2013 being short on tornadoes are diametrically opposed to those for the 2012 season.
In 2012, summerlike heat took hold early, meaning less jet stream energy, less moisture and more warm air capping aloft to deter rotating thunderstorms.
In 2013, winterlike patterns held deep into spring, delaying the start of tornado season until well into May.
But none of this is of any solace to Moore, Shawnee or El Reno, Okla. It’s not how many tornadoes happen that matters for human suffering; it’s where just a few intense ones hit.
Weather Journal runs on Wednesdays.
Weather JournalRain is here; watching for snow