Local meteorologists are anticipating a potentially active tornado season in Kansas this spring.
"I'm quite concerned this could be a very busy tornado season," said Mike Smith, president of WeatherData Inc., a Wichita subsidiary of AccuWeather.
There are two reasons for those concerns, he said: across the United States it has been wetter than it has been since the Palmer Drought Index was developed more than 40 years ago, and a high pressure dome over British Columbia is redirecting the jet stream right through Tornado Alley.
That's a combustible combination, Smith said.
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"In March and April, we have these weather systems come through that would be tornado-prolific, except they don't typically have enough moisture to work with," Smith said. "That's not going to be a problem this year."
That set-up brought snow storms every fourth day or so to the Plains, he said.
"That may turn into tornadoes every few days" somewhere in the heartland once temperatures begin to warm up, Smith said.
It's difficult to offer long-term forecasts for tornadoes, but local meteorologists look for clues where they can.
One theory gaining credence among researchers is the green line, or wheat belt, theory developed by the Oklahoma Climatological Survey.
The theory suggests strong thunderstorms form along a line of moisture created when winter wheat transfers water from the soil to the atmosphere.
"Wheat is very efficient in transferring moisture from the ground into the atmosphere," Cook said.
Temperatures have stayed stubbornly cool so far this year, delaying the greening of farm vegetation.
But it's been a wet winter in Texas, Oklahoma and Nebraska, so the wheat belt should emerge from its winter hibernation strongly, said Ken Cook, a meteorologist with the National Weather Service in Wichita.
That means the "green line" should set up in central Kansas, he said. That happened in 2007, the year of the Greensburg tornado outbreak.
Dry lines — where dry air clashes with warm, moist air — stall next to that moisture at night. When the sun heats up the atmosphere the next day, the dry line encourages instability —which is a vital ingredient for the formation of intense thunderstorms.
In addition to the wet winter and the green line theory, the jet stream also offers clues to how active the tornado season may be.
"All of us have been noticing a very active southern branch of the jet stream," KSN meteorologist Dave Freeman said in an e-mail. "If this pattern persists, it will eventually migrate further north with the warming of spring. That would potentially give us an active weather pattern."
Forecasters say it's difficult to offer long-range forecasts on something as unpredictable as tornadoes.
Research meteorologist Harold Brooks with the National Severe Storms Laboratory wrote in a blog post that the fact that only one tornado was recorded in the country in February sheds little light on the rest of the tornado season.
It means "somewhere between a little and nothing at all," wrote Brooks, who is based in Norman, Okla. "Most years that have started out with few tornadoes have ended up average or below. However, there have been big exceptions."
In 2003, for instance, tornado season was virtually silent through the end of April. Within a two-week period, however, so many tornadoes touched down the year was considered more active than normal.
"In the end, we will just have to wait and see and, of course, be prepared!" Freeman said.