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Why Hurricane Michael’s Power Caught Forecasters Off Guard

Floodwaters in Panama City, Fla., on Wednesday after Hurricane Michael made landfall.Credit...Eric Thayer for The New York Times

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Hurricane Michael was a sly storm, one that seemed almost unexceptional at first. It followed its predicted path with seeming obedience, but then burst into sudden fury as it approached the Florida Panhandle, reaching wind speeds at the cusp of Category 5 strength and leaving mud and rubble in its wake.

It was, in other words, a hurricane: the product of multitudinous forces that blend heat, wind and moisture into a potent threat, with a whopping dose of chance thrown in. Influences on the formation, direction and strength of hurricanes can involve faraway events like dry air from Saharan dust storms, the heated waters of El Niño in the Pacific, the undulations of the jet stream.

Increasingly, climate change is part of the dangerous mix as well.

Little wonder that modern weather modeling got its start in chaos theory, which acknowledges that small changes can lead to enormous effects so that, as one founder of the field put it, the flap of a butterfly’s wing in Brazil might set off a tornado in Texas.

As a result, no two hurricanes are alike. Storms like Hurricane Florence this year and Harvey last year moved slowly and dumped prodigious amounts of rain over the landscape. Katrina, in 2005, had weakened to a Category 3 storm by its landfall on the Gulf Coast, but delivered a smashing storm surge that rose 27.8 feet above mean sea level at Pass Christian, Miss.

In the case of Michael, the National Hurricane Center forecast the storm’s path with great accuracy, but its sudden intensification as it approached land was harder to predict. Millions of residents were caught off guard as Michael escalated from a tropical storm to a major hurricane in just two days, leaving little time for preparations.

[For the latest updates, read our Hurricane Michael live briefing.]

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This footage taken from a helicopter shows how Hurricane Michael’s powerful winds wiped out many parts of Mexico Beach, Fla.CreditCredit...Chris O'Meara/Associated Press

“This is really an amazing event,” said Andrew Dessler, a professor of atmospheric sciences at Texas A&M University. “It came out of nowhere and really intensified rapidly.”

Michael, he said, did not follow the common behavior of storms, which tend to weaken as they reach the shore because of interaction with the land. “It had the pedal to the metal all the way until it hit the coast,” he said.

[Read more about the links between global warming and hurricanes.]

Hurricane Michael’s sharp increase in strength as it approached Florida was due in part to its low barometric pressure, said Phil Klotzbach, a research scientist in the atmospheric science department at Colorado State University.

Low barometric pressure increases a storm’s intensity, and the barometric pressure within Hurricane Michael early Wednesday was just 925 millibars. There have only been a half-dozen storms that struck the United States with lower barometric pressure, the most recent being Katrina, Andrew and Camille — and all six “were devastating storms,” Dr. Klotzbach said.

While prediction of a storm’s path has grown increasingly accurate, the ability to predict rapid intensification has lagged somewhat, said Haiyan Jiang, an associate professor in the department of earth and environment at Florida International University.

The strengthening occurred despite pronounced wind shear in the region that might have been expected to weaken the storm, she added.

“The shear was high, so nobody expected it was going to intensify this rapidly,” Dr. Jiang said.

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A resident of Panama City assessed the damage to her home on Thursday.Credit...Joe Raedle/Getty Images

The biggest factor in the power of hurricanes is the difference between the temperature of the surface of the water they pass over and the coolness of the upper atmosphere.

Warm water is “basically the battery for, the fuel, that hurricanes feed off of,” said Jennifer Francis, a professor of atmospheric sciences at Rutgers University’s department of marine and coastal sciences.

The temperature of water in the Gulf of Mexico has been warmer than usual for this time of year, which helped make Hurricane Michael a powerhouse.

It is too early to say how much global warming contributed to Michael’s ferocity. But as the world heats up, we can expect stronger storms, said Adam Sobel, an atmospheric scientist at the Lamont-Doherty Earth Observatory of Columbia University. Together with Kerry Emanuel of the Massachusetts Institute of Technology and others, he has researched how warming waters increase storms’ wind force.

Even without the scientific calculations, he said, the connection makes intuitive sense. Hurricanes “form in places where the ocean’s surface is warmest,” and so warming oceans should mean stronger hurricanes — at least, among those that survive challenges like wind shear and reach maturity and strength.

“The rich get richer,” he said.

There is some evidence that this connection is already occurring, he added. “Michael could have occurred 100 years ago,” he said, “but there’s evidence that the probability of it is increasing as the climate warms.”

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Is Climate Change Making Hurricanes Worse? Yes, Here’s Why

Rising ocean temperatures have fueled some of the most devastating storms in recent years. Kendra Pierre-Louis, a reporter on The New York Times’s climate team, explains how.

Strong winds, deadly storm surges and a trail of destruction. Recent hurricanes have wreaked havoc in the United States. And you might be wondering, how does a hurricane work? So, the important thing to understand about hurricanes is that they only form over warm water. Think of warm water as the fuel to the engine that is a hurricane. A hurricane forms when warm air over the ocean rises. As that warm air rises, cool air sort of fills in below it, kind of creating that cyclonic action. At the top, it forms clouds, and those clouds create the rain system that we associate with hurricanes. So, many people are wondering, is climate change making hurricanes worse? Yes. Remember we talked about how warm water is the fuel for a hurricane? Because of climate change, the oceans are much warmer than they used to be. In recent years, we’ve seen very powerful hurricanes like Harvey and Florence. And the obvious question is, what do they have in common? Both of these hurricanes formed in unusually warm waters. Hurricane Harvey formed in waters around the Gulf of Mexico that were, on average, about 1 degree Celsius warmer than average. So, that’s a lot more energy going into the storm. So, does this mean we’re going to have more storms like this? The short answer is yes. The longer answer is storms like this are even worse. There’s some talk about potentially raising the hurricane category scale to include a 6 for stronger winds than we currently have. There is some concern or some evidence suggesting that hurricanes are moving further north. So, that means they’re going to show up in places that they haven’t traditionally existed and, potentially, even in places like Europe. When there’s a hurricane, when there’s a wildfire, climate change often comes up. But climate change is our new reality. And if we don’t take steps to mitigate it, we will continue to see powerful, severe hurricanes. And more and more people are going to be put in harm’s way.

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Rising ocean temperatures have fueled some of the most devastating storms in recent years. Kendra Pierre-Louis, a reporter on The New York Times’s climate team, explains how.

Climate change disrupts weather systems in more ways than one. A major report from the United Nations group known as the Intergovernmental Panel on Climate Change predicted weather crises around the world if nations fail to take serious action to curb the greenhouse gases that are causing the planet to grow hotter.

Such long-term projections of climate change are, in many ways, more dependable than short-term predictions of weather — which have, of course, improved greatly as well. The large forces at play in climate change, like the effects of accumulated carbon dioxide in the atmosphere, have been noted for more than 100 years. Modern models predicting warming have been borne out in thousands of studies showing phenomena like rising ocean temperatures and shrinking glaciers.

When it comes to hurricanes, climate scientists have said that the effects on storms are already being seen in heavier rainfall, as a warmer atmosphere holds more moisture. Sea level rise is beginning to bring higher storm surge, as well.

The wanderings of hurricanes vary widely, steered by wind currents and high- and low-pressure systems; some storms race across oceans and land while others dawdle. Hurricane Florence and Hurricane Harvey stalled, but Hurricane Emily in 1987 reached a forward speed of nearly 60 miles per hour over the North Atlantic, faster than a running cougar.

Hurricane Michael moved at an unexceptional speed of about 12 miles per hour across the Gulf of Mexico. But climate change could be affecting the pace of other storms.

Research by Dr. Francis of Rutgers suggests that warming in the Arctic could be weakening the jet stream in ways that, in the summer, can deprive weather systems like hurricanes of the atmospheric push that keeps them moving; those factors, she said, may have been at play in the unusual pokiness of Harvey and Florence.

As the Atlantic Ocean heats up along the Eastern Seaboard, Dr. Francis said, we can expect to see late-season storms persist longer and the East Coast become “much more friendly to tropical storms” like Hurricane Sandy, which carved a path of destruction in the Mid-Atlantic in 2012.

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In Inlet Beach, Fla., on Thursday, the sun shone on a toppled gas station.Credit...Emily Kask/Agence France-Presse — Getty Images

While there is growing scientific agreement on many of the theories about the effects of climate change on storms, there are also areas where consensus has yet to develop. “There’s still stuff we don’t know about hurricanes,” Dr. Klotzbach said.

Dr. Dessler, for example, said he was not certain that Arctic warming was having a pronounced effect on slowing storms like Harvey and Florence.

Still, he said, “the idea that hurricanes are going to stay exactly the same seems far-fetched.”

Whatever the changes wrought by climate change turn out to be, Dr. Dessler said, “Bad things are going to happen. I don’t know exactly what they’re going to be, but they’ll be things we don’t like.”

He drew an analogy to our wardrobes. “You’ve selected your clothes to fit you now,” he said, just as we are adapted to the present state of the global climate system. Whether we gain weight or lose it, he said, “no change makes your clothes fit better.”

For more news on climate and the environment, follow @NYTClimate on Twitter.

John Schwartz is part of the climate team. Since joining The Times in 2000, he has covered science, law, technology, the space program and more, and has written for almost every section. More about John Schwartz

A version of this article appears in print on  , Section A, Page 18 of the New York edition with the headline: Storm’s Sudden Intensification Surprised Even the Experts. Order Reprints | Today’s Paper | Subscribe

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