As Hurricane Ida closed in on the Louisiana coast on Sunday morning, meteorologists were stunned to watch the storm strengthen so quickly.
When Dale Eck, the head of forecast operations for the Americas at IBM, went to bed on Saturday night, he said, Ida’s winds were blowing at 105 miles an hour, which is Category 2-level wind speed. The next morning, he saw the winds had increased to 150 m.p.h., strong enough for a Category 4 classification.
“I got a sinking feeling in my stomach,” he said. “That was one of the worst-case scenarios.”
The storm had evolved swiftly from a worrisome disturbance in the Atlantic Ocean to possibly the most devastating to strike Louisiana since Hurricane Katrina in 2005.
Before Ida became a named storm on Thursday, forecasters detected what they thought was just another cluster of thunderstorms, or a disturbance, moving west over the Atlantic, said Ben Gelber, a meteorologist at WCMH-TV in Columbus, Ohio.
It quickly became clear that this disturbance was unique, because it was hovering in an area where the wind wasn’t fast enough to carry the ocean’s heat away from the system, Mr. Eck said. That allowed the heat to stay inside the system, creating the perfect humid environment for the disturbance to intensify into a tropical storm.
“It would have been hard to concoct a path more favorable to this rapid strengthening than Ida’s,” said Robert Henson, an independent meteorologist and a journalist for Yale Climate Connections.
Ida reached Cuba on Friday as a Category 1 hurricane, the lowest of the five hurricane classifications. From there, forecasters knew the storm would be intense, and the only question was just how bad it would get.
From Saturday into Sunday, a cauldron of weather conditions made Ida a devastating Category 4 storm: Its winds accelerated rapidly to 150 m.p.h.; a ridge of high-pressure air off the Southeastern United States shepherded the storm toward Louisiana; and the waters in the Gulf of Mexico were unusually warm and very deep, meaning that there was a lot water Ida could churn up to sustain itself.
The fact that the water was still warm was reason to worry that the storm could continue to strengthen to a low Category 5, said Benjamin Schott, the meteorologist in charge for the National Weather Service in New Orleans.
On Twitter, meteorologists across the country expressed alarm at how quickly Ida evolved into a colossal threat.
“I desperately wish the forecast hadn’t become reality,” said Rick Knabb, a hurricane expert at the Weather Channel, adding that rapid intensification before landfall is “the hurricane scenario we’ve always dreaded.”
Eric Blake, a senior hurricane specialist at the National Hurricane Center, said: “I feel sick to my stomach watching this hurricane. This is a very sobering morning.”