WITH ONLY ABOUT two-dozen twisters recorded so far this year during a period when 100 or more are typical, the US appears to be in a tornado drought.
Meteorologists say that cool, stable air is preventing the ingredients of the violent storms from coming together.
No US tornadoes have been reported so far in March, when tornado season often begins ramping up for parts of the country. The last time the US had no twisters in March was nearly 50 years ago.
Forecasters at the prediction centre reported earlier this week that since the beginning of the year, it has issued only four tornado watches and no severe thunderstorm watches.
This is less than 10% of the average 52 tornado watches issued by mid-March. The NOAA’s Storm Prediction Center in Florida hasn’t issued a watch in March, something that’s never happened.
“Every day that goes by is quite remarkable (because) we’re normally seeing very active day-to-day weather somewhere in the country,” said NOAA’s Greg Carbin. “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.”
Atmospheric scientist Adam Houston of 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.”
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