TULSA, Okla. (AP) - With only about two-dozen twisters recorded so far this year during a period when 100 or more are typical, the U.S. appears to be in a tornado drought as cool, stable air prevents the ingredients of the violent storms from coming together, meteorologists said Friday.
No tornadoes have been reported so far in March, when tornado season often begins ramping up for parts of the country. The last time the U.S. had no twisters in March was nearly 50 years ago, according to figures from the National Oceanic and Atmospheric Administration's Storm Prediction Center in Norman.
Forecasters at the prediction center reported earlier this week that since the beginning of the year, it has issued only four tornado watches and no severe thunderstorm watches - less than 10 percent of the average 52 tornado watches issued by mid-March. The center hasn't issued a watch in March, something that's never happened in its record of watches dating to 1970, said Greg Carbin, warning coordination meteorologist for NOAA's Storm Prediction Center.
"Every day that goes by is quite remarkable (because) we're normally seeing very active day-to-day weather somewhere in the country," Carbin said. "Four watches is also unprecedented."
Even in tornado-prone Oklahoma, the dominant weather pattern of cold, stable air that prevents a tornado's ingredients from coming together means the state is again starting storm season in sluggish fashion, a repeat of the year before, said state climatologist Gary McManus.
"We haven't had the prime conditions here in Tornado Alley because the predominant weather pattern doesn't lend itself to severe weather," McManus said. "Not only are we not seeing the tornadoes, we're not seeing the supercell storm systems that spawn these tornadoes."
Adam Houston, associate professor of atmospheric science at the University of Nebraska-Lincoln, cautioned that with spring just starting, so too is the peak time for tornadoes, and conditions are likely to change. For example, it was May when twisters raked the Oklahoma City suburbs of Moore and El Reno during a two-week period in 2013, killing dozens of people and injuring hundreds more.
"January and February are not active months, so (the tornado drought) hasn't been particularly surprising," he said. "If we're having this conversation in June, then there would be something substantial here."