How the weather service decides if a tornado touched down

Jul 10, 2014

At least four tornadoes ripped through central and northern New York Tuesday evening. It's the National Weather Service that makes that determination if a funnel cloud touched down. It's a careful and calculated process.

Armed with a compass, camera and notepad and paper the next morning, meteorologists Erik Heden and Mike Jurewicz retraced a storm that roared through Onondaga County, knocking down trees and power lines.

In East Syracuse, it was easy to find uprooted trees, their best pieces of evidence. 

"We really look at uprooted trees, they show us exactly how the wind was blowing last night," Heden said. "Tree branches, they’re cleaned up, they’re moved. That doesn’t help as much."

Strong winds and pounding rain tore through the village Tuesday evening. The power was still out as tree and utility crews were out en mass Wednesday trying to cleanup. 

Erik Heden, Mike Jurewicz and Chad Hecht from the National Weather Service.
Erik Heden, Mike Jurewicz and Chad Hecht from the National Weather Service.
Credit Ryan Delaney / WRVO

Heden and Jurewicz - along with a summer intern - were one of three survey teams out for the weather service on Wednesday.

That's rare for the weather service to have so many teams out and shows the wide swath of damage the storm system caused (a tornado was also confirmed in Pennsylvania).

Debris pattern

With the wind now calm and the sun out, Heden is looking at the pattern of damage the storm left behind.

"One thing we try to look for is how is the debris oriented," Heden said.

Powerful, straight-line storms, known as microbursts, leave trees spewed in a different way than tornados. 

"If you had a glass of water, that would be what a microburst would be," Heden explains. "You just dump it on the ground and it just spreads out. So the damage is either all in the same direction, or it’s in a fan shape."

Tornadoes bring circular winds, so tree trunks would be left pointing in the same direction.

"If it's coming together, it would indicate a tornado," he said.

That’s what killed four people in the Madison County town of Smithfield. The weather service says winds there blew more than 110 miles an hour, lifting homes clear off the ground.

Meteorologists say a tornado also tore through Deerfield, north of Utica, though less powerful. And in Lewis County, a 300 yard-wide tornado flipped cars and toppled trees as it blew 10 miles through Lowville.

There was no tornado here in East Syracuse, meteorologists determined, but winds hit 70 miles per hour.

When there’s a tree sitting on your house, Heden said, just what kind of storm knocked it down doesn’t really matter much.