Forecasters say a wetter-than-usual winter and a jet stream ripping over the part of the country known as "Tornado Alley" could lead to an active spring — perhaps starting with the strong twister that nicked a small western Oklahoma town Monday night.
"It's time to get ready," Michelann Ooten of the Oklahoma Department of Emergency Management said Tuesday as she surveyed damage from a storm that destroyed five homes and tore the roofs off several others in Hammon.
The nation typically will see 70-100 tornadoes by early March, but only 42 had been reported until Monday night's Oklahoma tornado. There was only one tornado nationwide during February.
"No one would argue that we're going to see a pretty good increase in the number of severe storms," said Greg Carbin, the warning coordination meteorologist with the national Storm Prediction Center in Norman, Okla. "But each year's a little different. The number, magnitude, number of days are all very tentative at this point."
In the short term, storms will be generated and fueled by the usual tornado trigger — Gulf moisture colliding with storm systems driven by the jet stream.
In a few months, parts of the Plains that had above-normal precipitation during the winter could see storms fueled by the moisture stored within plants and the ground. "Transpiration is usually a component later in the springtime. We won't have that for a little while longer," Carbin said.
Monday's twister occurred when a low-pressure system in the Pacific Northwest kicked a strong storm system out of the Rocky Mountains and into the southern Plains. "There are all sorts of connections," Carbin said. "The atmosphere is a dynamic thing. You can't really pin it down to one descriptor."
The slow start to the season is no sign that later storms will be stronger, weaker or non-existent.
"That pretty much tells us nothing," said Harold Brooks, a research meteorologist at the National Severe Storms Laboratory in Norman.
Brooks said that if the weather conditions that caused the Hammon storm — abundant moisture at the surface and a low pressure system in Northwest knocking the jet stream into Tornado Alley — are still in place when the warm weather arrives, then the upcoming tornado season might be ferocious.
"If we had this pattern in two months, that would mean something very different than we have now," he said.
The only twister reported nationwide in February was in a San Joaquin Valley oilfield in California two weekends ago. A year ago, there were 36 February tornadoes — and the year's deadliest was Feb. 10, 2009, at Lone Grove, Okla., where eight people died in a storm with winds estimated at 170 mph.
Last year, 1,156 tornadoes were reported nationwide and 21 people were killed by a tornado, according to the Storm Prediction Center. In 2008, there were 1,691 tornadoes and 126 tornado-related deaths.