An inspection team from the National Weather Service is on its way back to Sterling, Va. this morning after inspecting damage from last evening's storm in Harford County. The preliminary word from their three-hour tour of the Fallston area is that the damage was caused by a small twister.

"The damage we saw suggests that, yes, it was a tornado," said David R. Manning, warning coordination meteorologist for the National Weather Service's Baltimore-Washington Forecast office in Sterling.

There was no immediate estimate of the storm's intensity on the Enhanced Fujita Scale. "I didn't see damage that would suggest a strong tornado, but there was some fairly significant damage to trees and a lot of power lines were taken down."

"At this point it looks like it was on the ground for a few miles - less than 10 but more than 3," Manning said. ""We have not mapped out all the locations yet completely."  The twister's path of destruction stretched from near Fallston, southeastward to very close to Abingdon. Its width varied from 100 to 150 yards.

A Fujita rating and a better estimate of the length of the tornado's path of destruction across Harford County is expected later today in a public information statement to be published on the Sterling forecast office Web site. 

Manning was also part of the team that inspected damage from the F-0 tornado that ripped through woodlands north of Butler in northern Baltimore County on June 13. The Fallston damage suggests yesterday's storm was bigger - "a little wider and a little longer," he said.

The fast-developing thunderstorm boiled up over northern Baltimore County around 5:30 p.m., knocking down trees near Old York Road and Troyer Road in Monkton, and near Corbett Road in Phoenix. 

The weather service issued a severe thunderstorm warning at 5:35 p.m., Manning said, followed by a tornado warning for Harford County at 6:12 p.m.

The storm crossed into Harford County, snapping and toppling large trees in the Fallston area. Many of the trees took power lines and poles down with them. Utility and highway crews were still clearing and repairing the damage this morning.

Here's the story in this morning's Sun. 

Manning said he saw trees as large as 3 feet in diameter at the trunk that had been felled by the storm. "Some trees were topped, with either parts or most of them snapped off. Most of them were pushed over."

The key to distinguishing tornado damage from straight-line wind damage is the orientation of the downed trees and debris.

"If they diverge, it's straight-line wind," he said. He compared the effect to that of pouring a bucket of water onto the floor. The water moves out and away from the center. In a tornado, the debris is drawn in toward the center of the storm's track.

Fortunately, he said, yesterday's damage was almost entirely to trees and power lines. "A lot of the trees that fell, even though they were near homes, didn't fall on homes," Manning said. "I did see a few locations where limbs or trees did fall on homes, but I didn't see any major structural damage where I looked."

Accompanying Manning on the inspection tour this morning was another meteorologist from the Sterling forecast office, and a representative of Maryland Emergency Management.