Conservative predictions by the National Weather Service during Hurricane Isabel, communication breakdowns within the agency and confusing bulletins led D.C. area officials to underestimate the tidal flooding headed their way during the storm, according to a report released yesterday.

"Ninety-nine percent of what the Weather Service did was outstanding," said Russell Pfost, chief of an in-house team that wrote the critique of the agency's performance during Isabel's destructive march up the East Coast last year. "But we don't write service assessments to pat ourselves on the back. We are always trying to do a better job in how we communicate these forecasts."

The tidal surge caused by Isabel was one to three feet higher throughout the Chesapeake Bay region than the Weather Service predicted, the report said. Severe flooding hit Fells Point in Baltimore, the U.S. Naval Academy and downtown Annapolis.

In Virginia, a tidal surge from the Potomac turned streets into canals and basements into pools in Old Town Alexandria and in the Belle View neighborhood of Fairfax County.

Using what turned out to be overly conservative flood estimates from the Weather Service, emergency workers had built walls or piled up sandbags in many of those places. But those barriers were easily engulfed by flood waters.

In releasing the report, Weather Service officials emphasized a timeless fact: The weather is hard to predict.

"We don't profess to be perfect," said David Manning, who coordinates weather warnings for the Washington area out of the agency's Sterling office. "The Chesapeake Bay system and the tidal Potomac River system are extremely complex basins to forecast. . . . It's difficult to put an exact number on how high the water will get."

Although Isabel was downgraded to a tropical storm before it hit the region, it is considered one of the Washington region's most destructive natural disasters. It caused an estimated $5 billion in damage, according to the Weather Service report, including $925 million in Virginia and $410 million in Maryland.

In Virginia, 32 deaths were attributed to Isabel, according to the state Department of Emergency Management. In the state's history, only Hurricane Camille in 1969, which killed 153, was more deadly. In Maryland, the storm caused eight deaths. A traffic death in the District was linked to the loss of power to traffic lights.

In Isabel's aftermath, some local emergency officials said they were confused over whether the Weather Service's flood estimates were made on top of high or low tides; others wanted more specific forecasts. The storm also revealed the need for backup power for automated weather instruments, the report said.

In response, Weather Service officials said they have simplified bulletins and have improved the way local data are provided to authorities in emergencies.

During Isabel, the National Weather Service also struggled to coordinate information between its Sterling office and its Middle Atlantic River Forecast Center in Pennsylvania, according to the report. That problem has been resolved by hiring more staff, Manning said.

Despite the critique, there was little blame directed at the Weather Service yesterday for underestimating the flooding.

Instead, emergency managers complimented the agency for meeting with them well in advance of Isabel's arrival and for keeping in constant contact during the storm.

"I don't hold them responsible. They don't control the weather; they just try to predict the weather," said Douglass Bass, Fairfax County emergency management coordinator. "It just shows you that you can never anticipate the effects of a storm, especially a hurricane."

Fay Hobbs-Carter, a co-owner of the Christmas Attic, had four feet of water surge into her store and lost about $250,000 worth of goods and business. Her shop has had trouble recovering because whenever it rains, she said, people now mistakenly think Old Town shops will flood.

Still, she said it is absurd to blame the weatherman for her misfortunes. "To expect the Weather Service to predict everything is crazy," she said. "I don't think we are angry with anyone in particular except the hurricane."

Annapolis residents flocked to see the flooded City Dock; a report pinpoints some shortcomings in preparing for and responding to Hurricane Isabel.