For many years, meteorologists relied on the following rule: hurricanes do not survive when vertical wind shear is significant. The structured structure that a storm requires to intensify is destroyed by wind shear, which is the variation in wind direction and speed at different altitudes. The engine is knocked out of alignment. Florida International University research professor Hugh Willoughby put it simply: “Shear is death for hurricanes.” He described Hurricane Lee’s formation in September 2023, during an El Niño year that should have created precisely this type of adverse shear environment, as “a nasty surprise.” The mechanism that was supposed to stop it may have been overpowered by the unusually warm ocean beneath it. In direct answer, Willoughby said, “We, the theoreticians, need to think about that.”
Something about the current state of hurricane science is captured in that moment. Forecasters’ models are still largely based on the same patterns: shear destroys storms, warm oceans fuel them, and La Niña tends to increase Atlantic activity while El Niño suppresses it. However, the tremendous ocean warming that has been building up year after year has begun to challenge established trends in ways that even seasoned researchers were unable to fully predict. According to statistics monitored by several monitoring agencies, global ocean temperatures surpassed records every single day for almost a year before 2024. The water beneath storms is now hotter than it was in the past. More fuel is also produced by hotter water.
Coastal communities are most immediately impacted by the intensifying story. James Kossin, who tracked long-term storm trends for years at NOAA, gives a mechanical analogy to explain the mechanics without oversimplifying it: altering a carburetor’s jets to let more fuel in results in more horsepower and faster acceleration. A hurricane is affected in this way by warmer ocean surface temperatures. They make it possible for it to go from a mild tropical storm to a Category 4 in a shorter amount of time than it used to. With a speed that drastically reduced the warning window for Florida’s west coast, Hurricane Milton in the Gulf of Mexico in 2024 transformed from an organized storm to a Category 5. It’s challenging enough to predict a storm’s path. It is even more difficult to predict its intensity when the intensification curves are steeper than models predict.
Additionally, the season itself is evolving. Hurricane activity in the Atlantic has a fairly regular yearly cycle: it is quiet in the winter, intensifies in the summer, and peaks around September. The margins of that cycle are shifting, but it isn’t going away. Hurricanes don’t consult a calendar, as Kristen Corbosiero of the University at Albany points out with remarkable precision. The storms will act appropriately if the ocean conditions in June are similar to those that were once common in August. Although Suzana Camargo of Columbia University points out that it’s too early to declare a statistically significant shift, the exceptional early season activity in 2024, with Hurricane Beryl reaching major hurricane intensity earlier than nearly any storm on record, fits what climate scientists had predicted might happen as warming progressed. It’s a provocative indication. It’s not definitive yet.
The long-term data is most consistent at peak intensity. According to Kossin’s 2020 analysis, between 1979 and 2017, storm intensity rose by about 6% every ten years. Compared to forty years ago, storms are now around 25% more likely to exceed the 111 mph threshold that characterizes a major hurricane. The percentage of tropical cyclones that reach Category 3 and above is probably rising, according to the IPCC’s evaluation of the larger global record. Even while the overall number of named storms hasn’t grown significantly, the average hurricane season today has more destructive potential than it did a generation ago due to this combination: longer seasons, faster intensification, and stronger peaks.
