Tornado touched down in York County, damaging school, officials say

The National Weather Service determined that a tornado touched down Thursday in York County, damaging Eastern York High School and other buildings.

Federal, state and local officials were in York County on Friday morning to assess the damage from the powerful, fast-moving storm system that left a path of destruction on Aug. 20 in the area of the high school and continued on into Lancaster County.

The survey team, the weather service said, will be making a determination about the strength of the tornado after further review of the damage, according to the National Weather Service.

According to the National Weather Service, investigators will use wind speed estimates, the pattern of damage and where debris ended up on the ground to help determine whether a tornado was to blame. Ultimately, investigators may assign a rating to the storm on the Enhanced Fujita (EF) scale, a measure of how strong a tornado was.

Kyle Elliot, director of the Weather Information Center at Millersville University, if a tornado touched down, it was likely not very strong, quick-hitting, and didn't stay on the ground very long. 

"They touch down, the path is a couple of hundred yards long, they are on the ground for 1 or 2 minutes, and then they lift back off the ground and that's that," Elliot said. "This is very common for this part of the country" 

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The rotation it takes to sustain a tornado, he said, is often interrupted in areas with complex terrain.  

"We are in one of those areas with complex terrain," Elliot said. "There are the hills west of York, the terrain just east and west of the Susquehanna River with the big dip on either side of the river, tornados don't like that. That rotation pattern it takes to sustain them gets interrupted by those complex terrain features." 

It is very uncommon for areas in York and Lancaster counties, where most of the damage was, to get EF 3, EF 4 or EF 5 tornadoes. 

"It rarely happens in this part of Pennsylvania," Elliot said. 

Elliot said there are ways to tell from the debris pattern what sort of weather event occurred. He said the debris pattern from a tornado will look chaotic. 

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"Within a tornado, winds are rotating," Elliot said. "If a tornado moves through an area, with that rotation, the debris pattern that's caused by the tornado will look chaotic because winds within a tornado are blowing from all different directions." 

Officials are still working to determine the exact strength of the tornado that touched down in York County.

"A tornado is rated based on the damage it causes and also how strong the storm survey team thinks the winds within that tornado were," Elliot said. "They often estimate the strength of the winds within a tornado based on the damage the tornado caused." 

Radar imagery also helps in determining tornado strength, he said. 

If damage was caused by microburst winds, Elliot said that damage is more like a starburst pattern. 

"With a microburst, every tree is down in the same direction," he said. "Because of the microburst, you are also getting this downward motion from aloft, but it's also like a starburst pattern where is spreads out. 

With straight-line winds, damage comes in more of a horizontal pattern. 

"If you see downed trees and power lines, they are all blown from one specific direction to the other," Elliot said. "The damage is consistent from one direction to the other." 

If a tornado passed through York County Thursday, the power is measured by the Enhanced Fujita Scale, which ranks tornadoes from EF-0 to EF-5. 

"A tornado is rated based on the damage it causes and also how strong the storm survey team thinks the winds within that tornado were," Elliot said. "They often estimate the strength of the winds within a tornado based on the damage the tornado caused." 

Radar imagery also helps in determining tornado strength, he said. 

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This article originally appeared on York Daily Record: Tornado touched down in York County, damaging school, officials say