The warnings and maps seemed clear.
On Tuesday evening, the National Weather Service issued a prediction that a broad area of the Ohio Valley and Eastern Seaboard would soon receive heavy rainfall from Hurricane Ida. And one of the reddest parts of those maps—showing the high probability of severe rainfall and flooding—hovered directly over New York City.
Those predictions turned out to be true. But the record intensity of rain that fell more than three inches in an hour surprised the authorities. And on Thursday, as the death toll in the Northeast rose to 43, including 23 in New Jersey and 15 in New York, questions increasingly arose as to whether city and state officials were caught flat-footed by the speed of the storm. Had gone.
The destruction in the New York area seemed particularly striking, given that Ida had already blown through the Gulf Coast, hitting New Orleans on Sunday with very strong winds but with fewer deaths.
This came in the wake of a series of sometimes more powerful tropical storms – including the 2012 Hurricane Sandy – which has been repeatedly cited as a warning sign that the city's aging infrastructure and subways are due to climate change. are in the grip of violent weather to come. Subways, in particular, have begun to function as a default sewer whenever heavy rains overwhelm the city's actual sewer system.
The storm's devastation underscores the city's growing fragility in an era of global warming, but also highlights how the unpredictability of weather events can overturn even the best of plans.
The city issued an official warning on Wednesday morning, when the city's Office of Emergency Management warned that the remnants of Ida could cause flash floods. The city said it has also activated its flash flood emergency plan, which includes the cleaning of clogged catchment basins. It has put its downed-tree task force on alert.
According to the governor's office, state transport officials were dispatched to clear culverts and other drainage systems of debris, along with inspections and patrols to assess the rising waters. A range of tools – from chain saws to hand tools – as well as pumps and generators were deployed.
By Wednesday evening, the warnings had become even more dire. New Yorkers were warned of tornadoes and urged to move to higher ground. According to city officials, the city's 911 emergency system and 311 helpline started receiving calls around 8 pm.
For all that, the intensity of the rain stunned the forecasters.
Arthur Degatano, director of the Northeast Regional Climate Center at Cornell University, said Wednesday night's flash floods were caused not by a single hurricane but by several smaller storms, whose interactions with each other were difficult to predict. In the end, they ended up running over New York City, one after another, hurricanes.
"It was like New York City was on train tracks, and the storm was a train going down those tracks and they lasted for hours," he said. "I would say this storm, or the remnants of this storm, the forecast for heavy rain in the city the day before was actually pretty good. I don't think anyone would have imagined six inches of rain in a six-hour period at the time, inevitable in a manner."
Indeed, on August 21, Central Park received 1.94 inches of rain in an hour, a byproduct of Hurricane Henry and the highest rain-per-hour in record-keeping history. She broke that record by dropping 3.15 inches in an hour on Wednesday night.
Although no one could foresee the severity of two weather events 10 days apart, city officials released a citywide analysis of floods caused by rains in May.
The report tried to grapple with predictions that the city would experience an increase in "extreme rainfall events" during this century, including a potential 25 percent increase in annual rainfall and a substantial increase in the number of days with more than an inch . of rain.
Part of that plan included a commitment by the city to update its flash flood response processes. Among other things, it stated that by 2023, the city should "send messages of potential hazards to residents living in basement homes and have access to outreach and notification prior to predicted extreme rain events." "
He said the preparedness for flash floods in the city and elsewhere was not adequate in view of the loss of life and property in basement properties. "It's not waves from the ocean or sound," she said. "It's a flash flood coming from the sky."
Still, when rain falls at a historic pace, city officials say they can do little to prevent widespread flooding, given the age and condition of much of the city's infrastructure. The city's environmental protection commissioner Vincent Sapienza acknowledged on Thursday that the city was not prepared for such events.
"Anything over two inches per hour, we're going to have trouble with that," he said.