NASHVILLE, Tenn. – The National Weather Service failed to warn of major flooding in Nashville in the spring until after it had already taken place, and residents did not heed warnings because they didn't reflect the urgency of the flooding, which killed 22 people around the state, a new report shows.
The report released by the weather service on Wenesday found that the agency's river forecasters ignored two models that showed more accurate flood predictions for the Cumberland River. Instead forecasters favored a model that relied on inaccurate and untimely information from the U.S. Army Corps of Engineers. The weather service continued to use that data despite observations on the ground that proved their flood predictions were inaccurate.
"We can't stop the rain, but we can and must do a better job at warning people of the potential for dangerous flooding," U.S. Rep Jim Cooper, D-Nashville, said in a statement. "A few hours of warning could have saved lives and prevented millions of dollars in damage."
Record rainfall caused the Cumberland River to swell on May 1-2. According to the report, by early Sunday, May 2, and possibly earlier, officials at the weather service's Ohio River Forecast Center were concerned about a possible major flood of the river — defined as water levels of 45 feet and above at downtown Nashville.
Two other flooding simulations — one was experimental and the other didn't use the corps' data — both predicted major flooding, with a crest possibly reaching 54 feet. But after a conference call with the corps at 8:30 a.m. that morning, the weather service issued a public prediction of flood levels reaching only 41.9 feet, just below the "moderate" flood level.
That prediction relied on the corps' estimates of how much water it was releasing from dams. As a corps assessment of its actions during the flood previously found, the agency was constantly adjusting the flow from the dams but not updating the weather service about those changes.
The weather service report also makes clear that some of the flow data reported by the corps were not accurate even at the moment they were received.
On Sunday morning, the river exceeded the weather services' predicted 41.9-foot crest in less than two hours. The service continued to rely on inaccurate and outdated information from the corps even though on-the-ground observations showed the river rising much more rapidly.
The river eventually crested at 51.86 feet in downtown Nashville at 6 p.m. Monday. A more accurate prediction of a 51.5-foot crest did not come until 4 a.m. Monday. A 52-foot crest was not forecast until 3:42 p.m., according to the report.
The flooding was one of the state's worst natural disasters, causing over $2 billion in damage in Nashville alone. Many people have complained that they were not warned to evacuate their homes until it was so late they had to wade through flood waters to rescue boats.
The report also criticizes the wording of the flood warnings. On April 30, the weather service's Southern Regional headquarters sent an e-mail to local weather offices reminding them of the option to use "Flash Flood Emergency" in their warnings to the public. But the Nashville office never used the term "flood emergency," despite "the many reports of catastrophic flooding, water rescues, and even fatalities" the report states.
And the report found that staffing levels were inadequate for the emergency.
"At critical times, the office was overwhelmed," National Weather Service Director Jack Haynes said in a conference call.
The assessment notes that progress has been made in interagency communication and cooperation. Haynes also said that high-resolution flood maps are being developed for the Nashville area that will show down to the street level where flooding is expected.