Timing rather than a trend seems to be the key as to why Oklahoma has broken the state record for tornadoes in the month of April the past two years, according to weather officials.
In April 2011, there were 50 confirmed tornadoes in Oklahoma, breaking a record for that month previously set with 40 in 1957. This April, there were 52 tornadoes in the state. So do those 102 in two years mean April bypasses May as the month for the biggest threat of twisters in Oklahoma?
No, say the experts as they look over the official state records for tornadoes that date to 1950.
Gary McManus, of the Oklahoma Climatological Survey, said that to see if there is a change in our primary tornado season, you really have to look at the changes in the ingredients that form tornadoes. The weather patterns that have to come together are complex.
“With severe storms and tornadoes, it's all driven by very small-scale weather features,” said Rick Smith of the National Weather Service, Norman Forecast Office, “and whether we have four tornadoes or 50 or 100 in a month can be determined by the exact location and behavior of storms on one day, or even just a few hours.”
A closer look
There have been more tornadoes during April than May in the past two years and in five of the past eight years.
However, weather experts look to specifics rather than just the numbers.
“It could be a byproduct of drought, the La Nina/El Nino oscillation, or just plain short-term natural variability,” McManus said. “Now this year, April was more like May and May was more like June, climatologically speaking, and the types of storms we saw seemed to follow suit.
“Last year, the drought was intensifying in western Oklahoma during April and the storms were all forming in eastern Oklahoma. I'd have to ask, ‘Did the drought and heat in western Oklahoma help fuel the dryline in eastern Oklahoma, and also limit tornadoes during May?'”
And when looking at the numbers, consider other changes such a greater opportunity for confirming tornadoes.