The Old Hurricane Rules Are Gone

After several days of whirling across the Gulf of Mexico, blowing at up to 180 miles per hour, Hurricane Milton is tearing toward Florida as the terrible embodiment of a historically destructive season. Milton inflated at a near-record pace, growing from a Category 1 storm into a Category 5 behemoth in half a day, to become one of the most intense hurricanes in recorded history. The hurricane had already dispatched plenty of dangers, including at least five tornadoes, before weakening to Category 3 ahead landfall, which is expected tonight or early tomorrow morning. And the worst is still yet to come for millions of people in its path.

The 2024 Atlantic hurricane season was forecast to be monstrous, but what has actually happened is something more nuanced—and stranger. July began with Hurricane Beryl, a Category 5 storm that emerged much earlier than any other in history. Then, what should have been the busiest part of the season was instead eerily quiet. It was “fairly surprising,” Emily Bercos-Hickey, a research scientist at the Lawrence Berkeley National Laboratory, told me. Then, beginning in late September, came a tremendous burst of activity: Hurricane Helene, which broke storm-surge records in Florida and unleashed devastating rains far inland; a flurry of named storms that spun up in quick succession; and now Milton.

Hurricane experts are still trying to understand why the current season is so scrambled. The extreme storm in July, the sudden lull during the traditional hurricane peak in late August and early September, and the explosion of cyclones in October together suggest that “the climatological rules of the past no longer apply,” Ryan Truchelut, a meteorologist in Florida who runs the consulting firm WeatherTiger, told me. For Truchelut, who has been in the business for 20 years, “there is a dreamlike unreality to living through this time,” as if he’s no longer living on the same planet he grew up on. During that summer lull, this hurricane season seemed like it might be a welcome bust. Instead, it is an indication that our collective sense of what hurricane season should proceed is fast becoming unreliable.

The dire forecasts for the 2024 hurricane season were based on variables that are familiar to experts. This summer, Earth entered La Niña, which weakens the winds that can prevent hurricanes from growing too strong or forming at all. Meteorologists warned that record-high ocean temperatures across the tropical Atlantic and the Gulf of Mexico, along with the moisture stockpiled in our warming atmosphere, would fuel intense storms: four to seven major hurricanes compared with the usual three. Already, the 2024 season has conjured four major hurricanes. And it doesn’t end until November.

The mid-season lull, by contrast, was unexpected. Meteorologists also seem to have overpredicted the overall number of named storms—17 to 25 were forecast, and so far only 13 have arrived—though, again, there’s still time. “All the ingredients can be in place for an active or inactive season, but it’s the week-to-week variability that we can’t predict, but which often controls what happens,” Jeff Masters, a hurricane expert in Michigan who previously worked for NOAA, told me. Many Atlantic hurricanes are fueled by atmospheric conditions along the coast of western Africa. But this summer, the region stifled hurricane formation instead, thanks to an unprecedentedly heavy monsoon season. Scientists understand the basic mechanics of the quiet period. What experts can’t say, right now, is whether this scenario occurred because of natural happenstance. “We don't know for sure if that’s going to continue to happen with a warmer climate,” Bercos-Hickey said.

The summer hiatus isn’t the only way that this hurricane season has surprised meteorologists: More hurricanes than usual are making landfall in the mainland United States. After Milton, the season will be one more landfall away from tying the existing record of six. Hurricane experts have chalked this up to simple bad luck, just one more variable of hurricane activity that we can't do anything about. But humans bear some responsibility for the fact that the hurricanes that arrive are, on average, worse. Preliminary studies suggest that climate change made Helene 10 percent rainier and 11 percent windier. “Eleven percent may not seem like much, but the destructive power of a hurricane increases by 50 percent for every 5 percent increase in the winds,” Masters said. Scientists believe that global warming is making hurricanes intensify more rapidly, too. Milton, Helene, and Beryl all underwent rapid intensification this year.

This hurricane season may be charting slightly behind predictions, but “if we look at actual impacts instead of general metrics, it has been a catastrophic year,” Brian McNoldy, a senior research scientist at the University of Miami, told me. In Florida, residents had just begun cleaning up from Helene’s wrath when Milton emerged. Two weeks is not nearly enough time between two major storms, each one dialed up to unleash more water, whether from the skies or the seas, than they likely would have several decades ago. Meteorologists cannot perfectly predict the trajectory of any given hurricane season—too much is up to chance. Now, in Florida, millions of people are waiting to see what the odds will mean for them.