The polar vortex, for all the suffering it caused this winter, has brought about a major societal benefit: record-setting low tornado activity.
The crushing blasts of arctic air have squashed tornado formation. The twisters that have spun-up have been few and weak and have yet to claim a life this year.
The National Weather Service’s Storm Prediction Center (SPC) reports the number of tornadoes classified at intensity EF-1 or higher (on the 0-5 EF scale) this calendar year ranks lowest in 62 years of records and perhaps 100.
Greg Carbin, the warning coordination meteorologist at SPC, constructed the chart below which shows the years with the fewest (and most) number of EF-1 tornadoes through April 21, dating back to 1953.
“[The chart] reveals 2014 as the quietest year-to-date tornado period in over 60 years,” Carbin told CWG. “At an estimated 20 tornadoes through 21 April 2014, we are barely above 10 percent of normal (F1 and stronger)!”
This year’s 20 EF1 or stronger tornadoes compares to an average of 157 and pales in comparison to the record greatest number of 465 just three years ago (2011).
2014′s slow start may be unsurpassed even farther back than 1953. Carbin said his colleague Harold Brooks at the National Severe Storms Laboratory examined a mix of official and unofficial records dating back nearly 100 years and was challenged to find less tornado activity.
Of the small group of twisters that have touched down this year, not one has claimed a life, which is also a record.
“The last streak [without a fatality] that went this long was 2002,” Carbin said. “Prior to that you would have to go back into the early 1900s to find a fatality-free calendar year streak longer.”
The lack of tornado deaths reflects not only a lack of tornado quantity but also a lack of tornado strength. Dating back to late last fall, 155 days have passed without a tornado rated EF-3 or higher, the fourth longest streak on record.
Since late November, when the drought in intense tornadoes began, a persistent dip in the jet stream over the eastern half of the nation has opened the floodgates for arctic air intrusions, essentially shutting down the development of explosive thunderstorms, which are fueled by heat.
The extremely quiet start to the tornado season guarantees nothing about its future course, however. May and June, which average 276 and 243 tornadoes (based on records from 1991-2010) respectively, are usually the two busiest tornado months of the year in the U.S.