How unusual is this?

Hurricanes Helen and Milton devastated parts of the southeastern United States, ending an unusually busy tropical storm period.

In less than two weeks, five hurricanes formed, which is not far off from what typically occurs in the Atlantic Ocean throughout the year.

The storm is powerful and very fast.

However, there are particularly few storms in early September, when hurricane activity is typically at its highest.

So, how unusual is this hurricane season—and what’s behind it?

The season didn’t start well. July 2, Hurricane Beryl becomes the first Category 5 hurricane to form Atlantic Monthly’s records date back to 1920.

Just a few weeks ago in May, U.S. scientists warned June-November 2024 season could be ‘extraordinary’.

It’s thought that unusually warm Atlantic temperatures – combined with changes in regional weather patterns – will create conditions for hurricanes to form.

So far, with seven weeks left in the official hurricane season, there have been nine hurricanes — two more than the Atlantic typically sees.

However, the total number of tropical storms, which includes hurricanes and weaker storms, has been around average and lower than expected at the beginning of the year.

After Beryl weakened, there were only four named storms and no major hurricanes until Helen became a tropical storm on September 24.

Although the waters in the tropical Atlantic are warm, this should favor the development of these storms.

In the main hurricane development zone, which stretches from the west coast of Africa to the Caribbean, sea surface temperatures are about 1 degree Celsius higher than the average from 1991 to 2020, according to a BBC analysis of European climate service data.

Atlantic Ocean temperatures have been warmer over the past decade, mostly because climate change and a natural weather pattern known as the Atlantic Multidecadal Oscillation.

The secret to hurricane formation involves a complex mix of ingredients beyond seawater temperatures where none of these other conditions are suitable.

“challenge [for forecasting] Christina Patricola, an associate professor at Iowa State University, explained: “Other factors may change rapidly over timescales of days to weeks and may act in conjunction with the effects of sea surface temperature or offset.

Researchers are still trying to understand why this happens, but possible causes include a shift in the West African monsoon and large amounts of Saharan dust.

These hinder storm development by creating unfavorable conditions in the atmosphere.

But even during this period, scientists warn that the ocean remains unusually warm and severe hurricanes are still possible for the remainder of the season.

At the end of September, they arrived.

Starting with Helen, six tropical Atlantic storms were born in quick succession.

Driven by very warm ocean waters and now more favorable atmospheric conditions, these storms intensified, with five of them becoming hurricanes.

Five of them experienced so-called “rapid intensification,” in which maximum sustained winds increased by at least 30 knots (35 mph; 56 km/h) within 24 hours.

Historical data shows that, on average, only about a quarter of hurricanes intensify rapidly.

Rapid intensification can be particularly dangerous because rapidly increasing wind speeds may leave communities without enough time to prepare for stronger storms.

Hurricane Milton intensified at more than 90 mph in 24 hours, one of the fastest intensifications ever recorded, according to a BBC analysis of National Hurricane Center data.

Scientists from the World Weather Attribution Group found that wind and rain in Helen and Milton were worsened by climate change.

“This hurricane season is a clear indication that the effects of climate change are already being felt,” explains Andra Garner of Rowan University in the US.

“Storms like Beryl, Helene and Milton all intensified from relatively weak hurricanes to severe hurricanes in 12 hours or less as they passed through unusually warm waters.”

Milton also took an unusual but not unprecedented storm track eastward through the Gulf of Mexico, where the waters were unusually warm.

“It’s very rare [category] There were five hurricanes in the Gulf of Mexico,” said Feng Xiangbo, a tropical cyclone research scientist at the University of Reading.

Warming oceans make it more likely that stronger hurricanes will intensify quickly because it means storms can absorb more energy, which can lead to higher wind speeds.

U.S. forecasters are currently watching an area of ​​thunderstorms over the Cape Verde Islands off the west coast of Africa.

This could develop into another tropical storm over the next few days, but that remains uncertain.

As for the remainder of the season, high sea surface temperatures remain conducive to further storms.

It is also possible to develop Natural Anti-El Nino Weather Phenomena In the Pacific, it often favors Atlantic hurricane formation because it affects wind patterns.

But further activity will depend on other atmospheric conditions remaining favorable, which are not easy to predict.

Regardless, this season has highlighted how warm oceans caused by climate change are already increasing the likelihood of the strongest hurricanes — a situation that is expected to continue as the world warms further.

“Hurricanees occur naturally, and in some parts of the world they are considered a part of life,” explains Kevin Trenberth, a distinguished scholar at the National Center for Atmospheric Research in Boulder, Colorado.

“But human-caused climate change is putting pressure on them and increasing the risk of significant losses.”