A ‘Nightmare Scenario’ Hurricane Batters Mexico’s Western Coast

Hurricane Otis exploded onto the southwest coast of Mexico early Wednesday, shocking forecasters as it emerged as one of the more powerful Category 5 storms to batter the region and create what one expert called a “nightmare scenario” for a popular tourist coastline.

Few meteorologists initially thought the tropical storm would make landfall as a catastrophic hurricane. Most models failed to predict that the storm would intensify over the Pacific Ocean, leading forecasters to believe it would be at most a weak hurricane.

But it strengthened with remarkable speed, and by Tuesday evening forecasters and Mexican officials were rushing to warn residents of its potential for destruction.

The hurricane made landfall at 1 a.m. Wednesday local time, bringing heavy rain, flooding and mudslides to the states of Guerrero and Oaxaca, and cutting off power for more than half a million residents. The storm slammed ashore with sustained winds of 165 miles per hour; just a day earlier, Otis brought winds of 65 miles per hour.

Communication was almost entirely cut off from the popular tourist destination of Acapulco, a large port city home to more than 852,000 people that the National Hurricane Center warned was in “an extremely serious situation.” Residents said powerful winds ripped the roofs from buildings and swayed packed hotels.

“Rarely has a hurricane developed so quickly and with such force,” President Andrés Manuel López Obrador said during his regular morning news conference, adding that armed forces had been dispatched to Guerrero state.

It was unclear whether Otis had caused death or injuries in the region, which suffered major outages. But the hurricane “had an atypical behavior,” Mr. López Obrador said, who was on his way to Acapulco on Wednesday afternoon. “This has not happened in decades.”

The storm also caused SkyAlert, a popular earthquake warning app, to go offline, even as a relatively minor magnitude 4.4 earthquake was detected on Wednesday afternoon in Zihuatanejo, a city known for its luxury hotels and beaches in Guerrero.

Otis was downgraded to a Category 1 hurricane as it made its way over Guerrero state later on Wednesday morning, but it still unleashed “extraordinary rains,” dumping more than 10 inches across the state, according to Mexico’s national water commission.

That was particularly threatening to people living in the steep hills and ravines around Acapulco’s bay, which are susceptible to mudslides.

“This hurricane went directly over the fairly large city of Acapulco. That is not great news,” said Daniel Swain, a climate scientist at the University of California, Los Angeles. “It was the worst possible timing given that there was little warning.”

Caught in the middle of the hurricane was David Hall, 34, who traveled to Acapulco on Tuesday from Colima, a city about 300 miles away. Mr. Hall, who works in sales and was in Acapulco for a mining convention, said the hotel he was staying in, the Princess Mundo Imperial, had swayed in the high winds, making him feel like he was experiencing a “small earthquake.”

“It’s a very apocalyptic picture here,” he said in a telephone interview.

Mr. Hall recorded a video showing hundreds of people cramped inside a large meeting space — some were seen chatting among themselves, while others were sprawled across the floor.

“The wind was so strong, it was so much noise,” Mr. Hall said. “It was really terrifying. The wind was really, really fast.”

Now that the worst of the storm had passed and the weather was calming, Mr. Hall said he was hoping to be able to leave the city.

“I need to find a way to go back to my family,” he said. “This was a work trip, and it just turned over into a really bad situation.”

Residents in the state of Guerrero face the challenge of rebuilding their community, a task made more difficult after Mr. López Obrador dissolved Mexico’s Natural Disaster Fund, a pool of federal money for emergency relief.

The move was part of Mr. López Obrador’s push for budget cuts across the federal government.

The fund was once considered one of the world’s most effective means of providing disaster relief, said Alejandro Del Valle, an economist at Georgia State University. The aid accelerated economic recovery after a disaster, Mr. Del Valle and his colleagues found, and quickly restored access to health services — decreasing the number of deaths and easing bottlenecks in delivering disaster aid.

By law, the fund received 0.4 percent of Mexico’s federal budget every year, and if the money went unspent then it rolled into the next year. Now the country no longer has a regulated percent of the federal budget meant for disaster relief. Instead, the budget is revised every year and fluctuates based on other priorities.

Over the coming days and weeks, scientists will also assess why their forecast models were not able to predict just how powerful Otis would become.

A forecaster uses several tools to create a weather forecast, not just computer models. This is why meteorologists often say that a computer model isn’t a forecast — forecasters create forecasts, they like to say.

They also use satellite data and climatological norms to help form their predictions. They use satellite images to help estimate expected wind speeds and send hurricane hunter planes into storms to collect real-time data.

Global tools like an American weather forecast model and a European version haven’t always reliably predicted the rapid intensification of storms. New models focused specifically on hurricanes have been developed and this year they have proved useful, including predicting the rapid intensification of Hurricane Idalia well before that storm reached Florida, giving people in the state more time to prepare.

Still, as was the case with Otis, the tools are not foolproof. The result is a “nightmare scenario,” Eric Blake, a forecaster with the National Hurricane Center, wrote in a forecast on Tuesday night, as the storm approached southern Mexico and the intensity was becoming clear.

The storm began to organize itself on Sunday morning, first as a tropical depression. At that time, computer models didn’t show much to be concerned about.

Forecasters with the U.S. National Hurricane Center said that morning that “some slight strengthening” was possible over the following days. By Sunday evening, the computer forecast models were still not showing much.

By Monday afternoon, the models started indicating that the storm could become a hurricane, and forecasters believed that given the abundant moisture in the area and warm ocean temperatures, the storm would strengthen gradually.

On Monday evening, with Otis still a tropical storm, satellite images revealed what forecasters call a low-level structure, a common sign that the storm could intensify very quickly. But the models still weren’t showing this, so forecasters continued to predict that the storm would become a weak hurricane.

Even when Otis was still a tropical storm, there was enough evidence for Mexico’s government to issue a warning showing a stronger storm than the computer models were predicting.

On Tuesday afternoon, a hurricane hunter plane flew through the eye of the storm and found that its intensity was far stronger than the satellite estimates suggested.

That evening, with the storm clearly bearing down on Acapulco, the hurricane center issued a rare special advisory. “Rapid intensification observed earlier today has continued,” the forecasters wrote. “The environment isn’t forecast to change much before landfall, and there are no signs of this explosive intensification stopping.”

Around that same time, the mayor of Acapulco, Abelina López Rodríguez, posted an alarming warning on Facebook. “If your house is safe, don’t go out at all,” she said, adding that if your “home is at risk, go to a shelter NOW.”

On Wednesday, under constant rain in Chilpancingo, Guerrero’s capital, firefighters waded through brown water, while the authorities shined flashlights on splintered buildings.

By Wednesday afternoon, Otis was no longer a hurricane and its remains were crossing the rugged terrain of southern Mexico.

But in the places the storm ravaged, the extent of the destruction had not yet come into clear view.

“I’m mostly resigned,” said Priscila Villicaña, 31, a lawyer whose family lives in Acapulco. Speaking on the phone from Monterrey, Mexico, Ms. Villicaña said that at about 1:30 a.m. she had heard from her parents’ neighbors, who said the strong winds had ripped off the roofs of buildings and broken windows in downtown Acapulco, an area that, she said, is not usually flooded.

“I can’t imagine what happened later,” she said.

Reporting was contributed by Emiliano Rodríguez Mega and Elda Cantú from Mexico City; María Avilés from Chilpancingo, Mexico; and Eduardo Medina from New York City.