By Jesse McKinley, Dana Rubinstein and Jeffery C. Mays © The New York Times Co.
NEW YORK » The warnings and maps seemed clear.
On Tuesday evening, the National Weather Service issued a prediction that a wide swath of the Ohio Valley and the Eastern Seaboard soon would see heavy rainfall from what had once been Hurricane Ida. And one of the reddest portions of those maps — indicating severe rainfall and a high probability of flooding — hovered directly over New York City.
Those predictions proved true. But the record intensity of the rain, with more than 3 inches falling in one hour, caught officials by surprise. And on Thursday, as the death toll in the Northeast rose to 49 people, including at least 23 in New Jersey and 15 in New York, questions quickly arose as to whether city and state officials were caught flat-footed.
The destruction in the New York region seemed especially striking considering that Ida had blown through the Gulf Coast, hitting New Orleans on Sunday with far stronger winds but with fewer deaths.
It also came in the wake of a series of ever-morepowerful tropical storms — including 2012’s Hurricane Sandy — which have been cited as warning signs that the city’s aging infrastructure and subways are vulnerable. The subways, in particular, have come to act as a default sewer whenever heavy rains overwhelm the city’s sewer system.
The city issued official warnings early Wednesday morning, when the city’s Office of Emergency Management cautioned that the remnants of Ida could cause flash flooding. The city said it also activated its flash flood emergency plan, which involved cleaning out clogged catch basins. It put its downed-tree task force on alert.
State transportation officials were dispatched to clear culverts and other drainage systems of debris, according to the governor’s office, with inspections and patrols to assess rising waters. An array of equipment — from chain saws to hand tools — was deployed, as well as pumps and generators.
By Wednesday evening, the warnings had grown more dire. New Yorkers were warned of tornadoes and urged to move to higher ground. Calls to the city’s 911 emergency system and 311 helpline began to surge around 8 p.m., according to city officials.
For all that, the intensity of the rains surprised forecasters.
Arthur DeGaetano, director of the Northeast Regional Climate Center at Cornell University, said the flash floods of Wednesday night resulted from not one storm but several small storms whose interactions with each other were hard to foresee. In the end, those storms ended up running over New York City, one after another.
“It was just like New York City was on the train tracks, and the storms were a train going down those tracks and they persisted for hours,” he said. “I would say that the forecast for this storm, or the remnants of this storm, of heavy rain over the city a day in advance were actually pretty darn good. I don’t think anybody at that point in time could have imagined 6 inches of rain in a six-hour period, essentially.”
Indeed, on Aug. 21, Central Park saw rainfall of 1.94 inches in an hour, a byproduct of Hurricane Henri, and the most rain per hour in record- keeping history. On Wednesday night, 3.15 inches fell in one hour, eclipsing that record.
Mayor Bill de Blasio suggested that the experts had led the city astray.
He said that originally, the city was told to expect 3-6 inches of rainfall over the course of the whole day, something he cast as “not a particularly problematic amount.” Instead, he said “with almost no warning,” the city got the single biggest hour of rainfall in its history.
There was strong pushback to the mayor’s remarks, especially from elected officials who represent communities outside Manhattan.
“I think anyone who is saying they were surprised or caught off guard is being disingenuous,” said Justin Brannan, a councilman who represents Bay Ridge in Brooklyn and is chairman of the Committee on Resiliency and Waterfronts. “The one thing we can agree on is that these storms are getting more frequent and getting worse.”
Brannan is the sponsor of legislation that would require the city to develop a plan to protect the city’s entire 520 miles of shoreline. The legislation had 38 sponsors but has not moved in part to concerns over cost from the de Blasio administration.
Mitch Schwartz, a spokesperson for de Blasio, said the administration supported the “intent” of the legislation but said that studying even one neighborhood for a plan of that size would cost millions of dollars. The City Council may move to pass the legislation before February.