Milton was an unusual hurricane, but not unexpected. Here’s why

The hurricane has now weakened and moved off over to the North Atlantic Ocean, the National Hurricane Center, a US government agency, said on Thursday.

Milton occurred during the peak of the Atlantic hurricane season (mid-August to mid-October). Yet, scientists have said the storm is unusual in many ways — from how quickly the storm intensified to the path it followed — although not surprising. As the world continues to become warmer, scientists have repeatedly warned about such storms.

What was unusual about Milton?

Milton exploded from a Category 1 storm (they bring winds of 119 to 153 kmph) to a fierce Category 5 storm (they have winds of 252 kmph or higher) over the course of 12 hours between October 6 and October 7 morning. By afternoon, it had sustained winds of a whopping 285 kmph, becoming one of the strongest hurricanes ever recorded in the Atlantic.

A storm is said to undergo rapid intensification if its maximum sustained winds spike by around 56 kmph, according to a report by The New Yorker. Extreme rapid intensification takes place when wind speeds increase by 93 kmph. Milton’s maximum sustained winds spiked by more than 145 kmph in a day, the report said.

It was also rare that Milton formed in the Gulf of Mexico, which is connected to the Atlantic Ocean by the Straits of Florida, then began to move eastward, and made landfall on the Western coast of Florida. Jonathan Lin, an atmospheric scientist at Cornell University, told Vox, “There are not really any hurricanes on record that have done this and made landfall at a Category 3+ status.”

Guests at the Magic Kingdom at Walt Disney World brave wind and rain as bands of weather from Hurricane Debby pass through Central Florida. (AP)

Why was Milton an unusual storm?

The most crucial factor behind Milton’s intensification was the remarkably high sea-surface temperatures in the western Gulf of Mexico. The day Milton became a Category 5 storm, sea-surface temperatures reached nearly 31 degree Celsius, well above the 26 degree Celsius needed for hurricanes to develop.

Heat stored in oceans is a key ingredient in the rapid or extreme rapid intensification of hurricanes. “Put simply, hotter water evaporates more readily, and rising columns of warm, moist air from that evaporation fuel rapid intensification,” according to a Vox report.

Scientists say that the Gulf of Mexico’s unprecedented temperatures are primarily due to climate change. As the world continues to emit greenhouse gases, more heat is getting trapped in the atmosphere, a significant amount of which is absorbed by oceans. Global mean sea surface temperature has gone up by close to 0.9 degree Celsius since 1850, and around 0.6 degree Celsius over the last four decades.

Another reason for Milton’s severe intensity was the high humidity of the atmosphere. The atmosphere can hold 7% more moisture for every degree-Celsius increase in temperature. The increased moisture levels make storms more dangerous, leading to higher precipitation intensity, duration and/or frequency.

Lack of wind shear was also a factor. Wind shear is a change in wind speed and direction, and if it is strong enough, it can disrupt hurricanes. In Milton’s case, this did not happen. Kim Wood, an atmospheric scientist at the University of Arizona, told The Atlantic, “All of that combined is making the storm more efficient at using the energy available.”

Why are scientists not surprised?

In recent years, rapid intensification of storms has become more common. For instance, Hurricane Otis, which hit Mexico last year, became a Category 5 storm from a Category 1 storm within a day. Hurricane Idalia (2023) and Hurricane Ian (2022) are some of the other examples of rapid intensification.

Although more research is required to establish the impact of climate change on hurricanes, scientists believe that the spike in rapid intensification is a consequence of rising global temperatures.

A 2017 study, ‘Will Global Warming Make Hurricane Forecasting More Difficult?’, published in the Bulletin of the American Meteorological Society (BAMS), predicted that as the planet gets warmer hurricanes’ rapid intensification just before landfall was likely to become “increasingly frequent and severe”.

The situation is expected to only get worse. An assessment by several of the world’s leading climate scientists in the journal BioScience, published on Tuesday, said, “We are stepping into a critical and unpredictable new phase of the climate crisis… We will see much more extreme weather in the coming years.”