As Hurricane Milton exploded from a Category 1 storm into a Category 5 storm over the course of 12 hours yesterday, climate scientists and meteorologists were stunned. NBC6’s John Morales, a veteran TV meteorologist in South Florida, choked up on air while describing how quickly and dramatically the storm had intensified. To most people, a drop in pressure of 50 millibars means nothing; a weatherman understands, as Morales said mid-broadcast, that “this is just horrific.” Florida is still cleaning up from Helene; this storm is spinning much faster, and it’s more compact and organized.
In a way, Milton is exactly the type of storm that scientists have been warning could happen; Michael Wehner, a climate scientist at Lawrence Berkeley National Laboratory, in California, called it shocking but not surprising. “One of the things we know is that, in a warmer world, the most intense storms are more intense,” he told me. Milton might have been a significant hurricane regardless, but every aspect of the storm that could have been dialed up has been.
A hurricane forms from multiple variables, and in Milton, the variables have come together to form a nightmare. The storm is gaining considerable energy thanks to high sea-surface temperatures in the Gulf of Mexico, which is far hotter than usual. And that energy translates into higher wind speeds. Milton is also taking up moisture from the very humid atmosphere, which, as a rule, can hold 7 percent more water vapor for every degree-Celsius increase in temperature. Plus, the air is highly unstable and can therefore rise more easily, which allows the hurricane to form and maintain its shape. And thanks to La Niña, there isn’t much wind shear—the wind’s speed and direction are fairly uniform at different elevations—“so the storm can stay nice and vertically stacked,” Kim Wood, an atmospheric scientist at the University of Arizona, told me. “All of that combined is making the storm more efficient at using the energy available.” In other words, the storm very efficiently became a major danger.
That perfect combination—of hot seas, humid air, and little wind shear—is being aided by Milton’s path through the Gulf of Mexico’s western part, which hasn’t seen much major storm activity yet this season. When a storm passes over hot water, it sucks up much of that heat, using it as fuel and lowering the water temperature. But in the western gulf, “nothing else had been there to cool off the water,” Wood told me.
Milton is also a very compact storm with a highly symmetrical, circular core, Wood said. In contrast, Helene’s core took longer to coalesce, and the storm stayed more spread out. Wind speeds inside Milton picked up by about 90 miles an hour in a single day, intensifying faster than any other storm on record besides Hurricanes Wilma in 2005 and Felix in 2007. Climate scientists have worried for a while now that climate change could produce storms that intensify faster and reach higher peak intensities, given an extra boost by climate change. Milton is doing just that.
Rapid intensification has become more common in recent years. Hurricane Otis, which made landfall near Acapulco, Mexico, last year as a Category 5 intensified from a tropical storm in a single day, confounding forecasters and leaving residents very little time to prepare for a direct hit of that magnitude. Hurricane Idalia, also in 2023, was another example of rapid intensification, as was 2022’s Hurricane Ian. Kerry Emanuel, a meteorologist and professor emeritus at MIT, predicted less than a decade ago that hurricanes’ rapid intensification just before landfall was likely to become “increasingly frequent and severe as the globe warms,” and in the past few years, that prediction has borne out in additional modeling studies. It’s a new addition to the canon of climate-change knowledge, so it’s not yet firmly established, but this early research points toward a connection between rising temperatures and these storms’ rapid escalation. Climate change might actually decrease the total number of tropical storms and hurricanes (though the mechanism causing that decrease is still being debated), but the storms that do manage to form will likely be more intense, according to Tom Knutson, a senior scientist at the National Ocean and Atmospheric Administration’s Geophysical Fluid Dynamics Laboratory. His recent research found that more storms may make landfall in the U.S. as Category 4s and 5s by the end of this century. Even if we get fewer storms, they will be worse.
Trying to ride out storms of that size can be deadly. Overnight, Milton downgraded to a Category 4 but grew in size. It could also still reintensify to a Category 5. Florida is now preparing to evacuate potentially more than 6 million people ahead of Milton’s predicted landfall. And the conditions it will collide with on shore have already been worsened by climate change. The Gulf of Mexico has seen twice the global average rate of sea-level rise since 2010, according to an analysis by The Washington Post, and the sea along the Tampa Bay coast is now nearly five inches higher than it was 14 years ago. So when the storm surge floods the coast, salt water will probably travel farther inland, and likely with more force, than it would otherwise.
Milton also looks like a “very wet” storm, Gabriel A. Vecchi, a climate-science professor at Princeton University, told me, and Florida is already sopping wet. The state has been inundated with rain, and more will precede the storm. The ground is already saturated and so is unable to act as a sponge; ordinarily, it would serve as a partial buffer against flooding.
Rainfall is one of the best-understood areas of “attribution science,” the discipline that models how much worse climate change likely made any given weather scenario. And climate change is quite clearly making hurricane rainfall worse. Wehner and two colleagues at the Lawrence Berkeley National Laboratory put out a provisional analysis that found that, in some places in Georgia and the Carolinas, climate change may have caused as much as 50 percent more rainfall during Hurricane Helene. “Instead of 10 inches, they got 15 in some places. Instead of 20 inches, they got 30,” Wehner told me.
Only after Milton passes will scientists try to account for the ways that climate change made it more horrific than it might otherwise have been—perhaps still a major storm, but not so intense and so fast that it stopped a veteran meteorologist cold. And the world is expected to keep warming dramatically over the coming century; storms such as Milton are a preview of the types that will become more common, Vecchi told me. “We’re having a hard time dealing with storms this wet,” he said. “How are we going to do with storms that are wetter?” Surely those, too, will be shocking. But they should not be surprising: We’ll have known all along that they were coming.