What spurred the Great Smoky Mountains wildfire?

Many people were surprised to discover that the latest wildfire to wreak havoc in the United States occurred in Tennessee, rather than out West where these are far more common.

Thousands had to flee the resort towns of Gatlinburg and Pigeon Forge in the Great Smoky Mountains overnight Monday as intense winds spread the wildfire across roughly 500 acres.

Tennesse Gov. Bill Haslam called the fire that has killed at least three people “the largest fire in the last hundred years in the state of Tennessee.”

Heath Hockenberry, the national fire weather program manager for the National Weather Service, said that wildfires actually break out in the Southeast roughly every three to five years. That’s not nearly as often as the frequency in the West, but they’re not unheard of.

“When you’re talking about southeastern fires, they do arise here and there. I wouldn’t say a regular frequency,” Hockenberry said to Yahoo News. “I’ve personally been in north Georgia for fires that lasted nearly a year. But they don’t happen every year like this like they do in the western United States.”

The so-called Chimney Top fire that broke out in Tennessee was the result of several factors. Hockenberry explained that a northern-leaning jet stream has kept the cold air locked up in the northern parts of North America so that there’s been tremendous warmth. Low-pressure systems that typically bring moisture up from the Gulf of Mexico in the fall months haven’t materialized.

And there’s been a lack of rain for which the East was not prepared.

Hockenberry explained that the trees, bushes and understory (the layer of vegetation under a forest’s canopy) in the East actually dry out much more quickly than their counterparts in the West because they have not adapted to the same arid conditions.

Western vegetation is accustomed to dealing with a lack of rain. Eastern vegetation is not.

“The fuels in the Great Smokies really do need the rain in frequent intervals and become stressed a lot more easily than the western wood or even the understory. You can go 7, 14, 21 days here in the West and not have any fires start.”