The Edmond Sun

March 25, 2013

Forecasting tornadoes remains unpredictable

James Coburn
The Edmond Sun

EDMOND — Predicting how likely the occurrence will be this spring for severe thunderstorms and tornado outbreaks in central Oklahoma is difficult to know outside a 10-day range, said meteorologist Marc Austin, a forecaster with the National Weather Service in Norman.

Being in the southern plains gives Oklahoma a geographical bias for experiencing extreme weather, Austin said.

“Having been in a drought for the last three to four years has led to more dramatic changes,” Austin said. “One of the things we look at when we’re possibly forecasting tornadoes and severe storms is we want to get good quality moisture in here from the Gulf.”

Persistent drought with hotter temperatures and dry air is less favorable for severe weather, especially in June and July, he said. Now through early May is the climatological peak time for tornadic activity. Surface evaporation also applies moisture to the atmosphere.

“I’m sure we’ll see some, but right now it’s pretty impossible to tell whether we’ll be above average or below average,” Austin said.

Extreme drought continues from Texas north into South Dakota, he said. Much of the area remains in exceptional drought conditions, he continued.

“Unfortunately, even though we’ve had decent snow events, it’s still not added up to much,” Austin said. “There’s been some relief across northwestern Oklahoma.”

Large springtime storm systems tend to strengthen as they pass east of the Rocky Mountains. Severe weather events form when upper level winds are strong  and are combined with a jet stream dipping down south from the plains, Austin said.

“In the spring we’re in a good position where we see a good juxtaposition of a lot of instability,” Austin said.

Drought does not necessarily exclude severe weather outbreaks. Tornadic activity ripped through Oklahoma during drought conditions on May 24, 2011. An EF-4 tornado with winds from 166-200 mph created a  75-mile damage path and included 10 fatalities, according to the NWS and the Office of the Chief Medical Examiner.

There’s no doubt that storm systems will bring severe weather to central Oklahoma this spring. But Austin said only time will tell how frequent severe activity will be.

“It certainly can happen,” he said.



TO LEARN MORE about severe weather forecasting, go to http://www.noaa.gov.