Storm damage surveys continued late yesterday in the wake of Sunday's violent weather. But the count of tornadoes that raked parts of Maryland over the weekend remained at two.
Storm damage reported in Towson, Lutherville and Hunt Valley fell far short of the criteria for tornadoes after a survey by Christopher Strong, warning coordination meteorologist for the National Weather Service's Baltimore-Washington Forecast Office in Sterling, Va.
"We saw a couple of branches down," he said. "That was about the extent of it."
But the damage patterns in Charles and Prince George's counties did indicate that two relatively weak tornadoes touched down there.
Sunday's storms provided a curious prelude for a meeting in Linthicum of several hundred emergency management officials, who convened yesterday for the Maryland Emergency Management Agency's 23rd annual Severe Storms Awareness Conference.
On the meeting's agenda: a talk titled "Tornado Damage Assessment - Recognizing the Signs." It was delivered by Strong and William Sammler, the warning coordination meteorologist at the National Weather Service's Wakefield, Va., forecast office.
After the meeting, Strong was dispatched to survey the Baltimore County damage.
The storms also damaged Glyndon United Methodist Church and sparked a fire, the pastor said yesterday. The roof of the bell tower burned, but smoke and water damage were primarily confined to an area behind the sanctuary, said the Rev. Norman Obenshain. There were no injuries.
A fire at a home under construction on Wrights Mill Road in Randallstown also might have been started by a lightning strike, said Elise Armacost, a Fire Department spokeswoman. The fire was reported about 6:30 p.m.
Lightning also knocked down a chimney at Nabbs Creek Cafe at Maurgale Marina in Glen Burnie, and triggered a fire in a home in the 7700 block of Ricker Road in Severn. A woman in the home escaped without injury. Damages were put at $20,000, fire officials said.
Storm surveys in Southern Maryland found evidence of two tornado touchdowns, one northeast of La Plata in Charles County and the other west of Hyattsville in Prince George's County. Both, apparently, were caused by the same "parent" storm.
The tornadoes were rated as relatively minor EF-0 and EF-1 twisters on the "Enhanced Fujita Scale," with maximum wind speeds of 80 mph and 100 mph, respectively.
The first touched down about 2:10 p.m. in the town of St. Charles, according to the National Weather Service.
The winds snapped or uprooted several large trees. Some trees fell on houses and vehicles. Several homes lost roof shingles and sections of siding. A large shed was moved off its foundation and had its doors blown out.
The storm stayed on the ground for about two miles, with a width of 50 to 100 yards, the weather service said.
Strong said it was the strong rotation seen on radar at Andrews Air Force Base, the two-mile path of storm damage and damage evident in photographs from emergency managers that cinched the finding.
After hitting, the twister lifted, and the storm moved north, he said. About 2:40 p.m., another funnel touched down in Chillum in Prince George's County, causing tree damage at a water park.
The tornado then intensified, according to the damage assessment team. It crossed woods behind the George E. Peters Adventist Elementary School, lifted a portion of the school's roof and hurled it onto a downwind parking lot.
A construction trailer at the school was overturned, and debris broke windows at the Metropolitan Adventist Church across the parking lot. A slab of plywood was blown into a county fire station, knocking out its electrical service.
A firefighter told weather service officials that he saw rotation in the debris.
"Putting it all together, each individual thing makes more sense if it was a tornado rather than straight-line winds," Strong said.
Storm surveys are required by law. The results help forecasters improve the reliability of their warnings, and serve the needs of emergency managers, property owners and the media, Sammler said.
But there's a lot of mythology about tornadoes for the experts to sort through.
For example, demolished homes, unroofed houses, snapped, twisted trees and road signs and reports of "roaring" winds can all be caused by straight-line winds, Sammler said.
Among the clues that point to a tornado:
A narrow, concentrated path of damage is more indicative of a tornado than widespread, diffuse damage.
Impact damage on several sides of buildings. Straight-line winds result in damage on just one side.
Debris, such as roof sections, hurled in directions different from the storm's track.
Trees that are partially debarked and totally defoliated have likely been hit by a tornado.
All these kinds of clues, and more, have been incorporated into the new Enhanced Fujita Scale of tornado intensity, which was developed with the aid of physicists and structural engineers, and adopted last year by the weather service.
The new scale gives surveyors 28 damage indicators based on the types and ages of the trees, vehicles or buildings affected, and the damage that's evident.
They consider the full range of damage they see - both what was affected and what wasn't. That provides them with a range of likely wind speeds from which they can assign an EF scale number.
Sun reporters Nicole Fuller and Mary Gail Hare contributed to this article.