Despite quiet 2012, surprise strong tornadoes made an appearance

As quiet as last year was for tornadoes, 2012 still managed to deliver a number of surprise twisters – more than one of them in Kansas.

Several times, weather researcher Jon Davies said, strong tornadoes developed from storms that didn’t appear to have the ingredients to produce them.

A prime example, he told a crowd at the annual storm chasers convention in Denver recently, occurred in south-central Kansas on May 19. While showers and thunderstorms were expected, he said, the atmosphere wasn’t right for supercell thunderstorms to form.

The most forecasters were expecting were a few landspouts.

“Most landspouts are pretty weak,” Davies said.

Yet more than half a dozen tornadoes touched down, including two EF3s near Rago in Kingman County. One heavily damaged a wind farm.

“How could strong, long-lived tornadoes form in this setting?” Davies asked.

The turning of winds near the Earth’s surface – a key ingredient to the formation of tornadoes – was missing from central and southern Kansas on May 19. But a cool front coming from the southwest intersected with the south end of the boundary along which storms were forming, providing the low-level rotation that triggered the stronger tornadoes.

Davies said a similar scenario produced the EF5 tornado that slammed into Jarrell, Texas, in 1997, killing 27 people.

One of the other surprising tornado outbreaks in 2012 occurred after midnight on April 27 in southeast Colorado, something that hasn’t happened since 1942.

“My jaw dropped,” Davies said. “Climatologically, you don’t get tornadoes in southeast Colorado after midnight.”

But a tongue of warm air from the Gulf of Mexico swept northwest under a ridge of cold air, creating enough instability and providing enough moisture for strong thunderstorms to develop even without the assistance of daytime sunshine. The result was five tornadoes near Lamar – four of them EF2s, Davies said. Eight people were injured in the outbreak.

There were other unexpected tornadoes last year, he said, including a strong one near Norfolk, Neb., that touched down after a cold front moved through. Typically, when a cold front moves through an area, it stabilizes the atmosphere, robbing tornadoes of the instability they feast upon.

One of the important lessons from such storms is this, Davies said after his presentation: Just because tornadoes aren’t considered a threat with a given thunderstorm, people should nonetheless be ready to seek shelter.

Whether it’s the arrival of damaging straight-line winds or a slight shift in atmospheric conditions that quickly make tornadoes favorable, he said, it’s wise to be prepared.