Tornadoes have been few and far between this year — a relief to residents of Tornado Alley, but a letdown to scientists studying the swirling storms out in the field.
While tornadoes can occur at any time of year, spring is historically the most active period for the storms.
Many tornadoes have been spotted this year and several have caused damage to homes and businesses around the country, particularly in the usual hotspots of the Midwest and Southeast. But this storm season has been quieter than usual overall, particularly when it comes to the most intense killer storms.
To date, there have been 839 tornadoes this year, compared with 1,304 through the end of June last year.
"We haven't had as many tornadoes as we had last year," said Harold Brooks with the National Severe Storms Laboratory in Norman, Okla. Those tornadoes that have touched down this year also haven't hit as many populated areas, limiting the amount of damage they have done.
The unusual calm is due to weather patterns that have stifled the conditions that favor tornado formation, said AccuWeather.com Senior Meteorologist Henry Margusity. The season is likely to stay subdued since summer conditions aren't as favorable to tornado formation, Brooks said.
April was a bit more active than in past years, with 270 reported tornadoes according to preliminary estimates (which can be revised downward) by the National Weather Service's Storm Prediction Center in Norman, Okla. The three-year average for that month is 200 tornadoes.
May and June have had smaller tallies, particularly compared to last year: In May 2008, there were 461 tornadoes (higher than average), while this year there were only 227 in the same month.
The most striking difference comes in the number of tornadoes that have claimed lives. As of the end of May this year, there have only been nine killer storms, compared with 29 at the same point last year and 23 for the three-year average. Only 21 deaths have been reported this year, compared with 114 by the end of May last year.
"Last year was a big year for fatalities," Brooks told LiveScience.
While the lull in storms is good news for people living in storm-prone areas, it was disappointing for a team of meteorologists chasing storms this summer in order to learn more about what makes them tick (a project called VORTEX2). The project is finished for the year, but will begin again during the peak of the season next year.
"We didn't get as many events as you would like to have," Brooks said. "Hopefully next year we'll be able to get more."