Forecasters had been saying all day Tuesday that overnight thunderstorms could produce "strong, gusty winds" in some locations across the Baltimore-Washington area.
But the severity of the storms that raked Northeast Baltimore and Parkville just after 1:30 a.m. — ripping off roofs as residents slept, tossing cars about, toppling large trees and cutting power for thousands — was unexpected, the National Weather Service said.
"The widespread nature of it, and the outcome across the Baltimore-Washington area, was more than anticipated," said Bryan Jackson, a meteorologist at the Baltimore-Washington Forecast Office in Sterling, Va.
It was certainly more than Steven Pinder expected after he went to sleep in the Pinewood Avenue apartment he shares with his wife, three children, ages 6, 11 and 12, and a cousin.
"I just fell asleep, and the house started shaking," he said hours later at an emergency shelter. Outside, the air was a white, swirling cloud of rain and debris. Then, he said, "I heard popping and banging, glass shattering, just like a nuclear bomb was going off."
In fact, the roof was lifted off his apartment building, opening it to the night sky and the storm. Pinder and his family escaped, covered in white dust but unharmed. As he waited for permission to return to his place, he feared he'd lost everything except his car and the clothes on his back.
The National Weather Service sent a team to the area Wednesday to examine the damage and determine whether it was caused by straight-line winds or a tornado. At 6 p.m., however, the forecast office in Virginia issued a statement saying that the team was "awaiting additional information." A final survey report is expected Thursday.
"They're still awaiting more pictures of the damage from other people. They want to go back and look at the radar, match the damage to the signatures on the radar at various times," said NWS meteorologist Brandon Peloquin. "They'll put everything together [Thursday], make the determination and give all the details."
If the damage is attributed to a tornado, it could be ranked as high as an EF-1 or EF-2 on the Enhanced Fujita Scale. According to that scale, EF-2 twisters, with winds of 111 mph to 135 mph, can tear roofs off well-constructed houses, snap or uproot large trees, generate "light-object missiles" and lift cars off the ground. Evidence for each of those things could be seen Wednesday in Northeast Baltimore. For example, Baltimore Mayor Stephanie Rawlings-Blake said she saw "two-by-fours piercing the sides of buildings like spears" on her tour of the damaged areas.
No tornado watch or warning was posted for the area overnight, Jackson said. Looking back at the radar, however, he said "there was some rotation with that, and along with speed shear, there was directional shear, which would be conducive for tornadic development."
As traumatic as the damage was, however, the storm was not unprecedented.
Powerful thunderstorms damaged 150 buildings in a densely populated city neighborhood in 1994, putting 200 families out of their homes. Marylanders were hit by two violent storms in the span of a single week in November 1989, The Sun reported. On a Friday morning, winds felled power lines and trees, depriving around 80,000 homes of power and injuring one man seriously, though weather officials confirmed there were no tornadoes. The following Tuesday, 60-mph gusts knocked out power to 19,000 homes and killed an elderly woman when a warehouse collapsed onto her brick rowhouse.
Nor was Tuesday's storm a total surprise. All day, an intense low-pressure system was moving north and east along the west side of the Appalachian Mountains. Trailing out behind it was a cold front that, by nightfall, stretched from central Pennsylvania south into central North Carolina, moving to the east.
A hazardous-weather outlook posted all day Tuesday for Central Maryland noted that "isolated thunderstorms are possible this evening along and east of the Blue Ridge" as that front pushed east. "While most storms are not expected to be severe … the strongest activity could produce strong gusty winds," forecasters said.
As the front crossed West Virginia in the evening, the storms were not quite strong enough to trigger severe-storm warnings, Jackson said. "But they did intensify as they crossed east over the Appalachians."
By midnight, there was a broken line of strengthening storms along the front.
At 12:05 a.m., NOAA's Storm Prediction Center in Norman, Okla., issued a severe thunderstorm watch for Central and Eastern Maryland, the District of Columbia, Delaware, southeastern Pennsylvania and northeast Virginia, and said people in the area should "listen for later statements."
By midnight, of course, most people are asleep.
At 1:02 a.m., a severe-storm warning was posted for Baltimore city and county, along with most of Central Maryland from Carroll and Harford counties south to St. Mary's.
It warned of "a line of severe thunderstorms capable of producing damaging winds in excess of 60 mph. … This is a dangerous storm. If you are in its path, prepare immediately for damaging wind gusts and frequent cloud-to-ground lightning. Move indoors to a sturdy building and stay away from windows."
The warning was repeated at 1:20 and 1:40 a.m., then canceled for the city at 1:49 a.m. as the storm moved away to the east. The damage was already done.
More than 46,000 electricity customers lost power in the storm, most in Anne Arundel County, according to BGE's website. All but about 600 had had their power restored by 9 p.m. Wednesday.
The weather service also reported 30- to 40-inch-diameter trees knocked over in Virginia and a cinderblock wall failure at a UPS facility in the District of Columbia.
Baltimore Sun reporter Yeganeh June Torbati contributed to this article.