Atlantic hurricane season forecast to be milder than normal thanks to El Nino

Eighteen other groups, private and academic, have also forecasted what they think the season will be like and most of them also call for a below average summer and fall. Those other forecasts average a dozen named storms, only five becoming hurricanes and two of those being major ones. Those forecasts also call for the Accumulated Cyclone Energy index, which takes into account strength and duration of storms, to be 80% of normal.

Colorado State University, which pioneered the science of hurricane seasonal forecasting in 1984, is predicting the lowest overall activity since 2015, which was the strongest El Nino in the last 75 years. And that forecast is likely to be revised to even lower numbers in June, said Colorado State's hurricane expert Phil Klotzbach.

This is after nine of the last 10 Atlantic hurricane seasons have been above normal or even hyperactive, Klotzbach said. Last year started slow, but then had a burst, producing a near-record total of three Category 5 hurricanes, including Melissa which devastated Jamaica and Cuba, said Suzana Camargo, a climate scientist and tropical weather expert at Columbia University.

Inflation adjusted damage across the globe from tropical cyclones has increased from an average of $11.4 billion a year in the 1980s to $109.7 billion a year over the past ten years, with three-quarters of the damage done in the Atlantic, Gulf of Mexico and Caribbean, according to insurance giant Munich Re.

Hurricane, typhoon and cyclone are the same weather event, with the different names being used in different parts of the world.

“We should expect a less active year than certainly what we’ve seen recently, and perhaps significantly so below average,” said University at Albany atmospheric scientist Kristen Corbosiero. “But again, it only takes one to cause real devastation and destruction in the mainland U.S. or even in Hawaii.”

El Nino decapitates Atlantic storms

It's mostly because of “the elephant in the room” which is an El Nino, Camargo said.

An El Nino is the natural and cyclic warming of parts of the central Pacific that warps weather patterns around the globe, especially during winter. Scientists for decades have found a correlation between an El Nino and below average Atlantic hurricane activity and stronger and more storms in the central and eastern Pacific. This year many forecasts are calling for a strong, super-strong or even record setting intense El Nino. During a La Nina, the cool flip side of El Nino, the Atlantic is generally busier with stronger storms.

There's a 98% chance that there will be an El Nino this summer and an 80% chance it will be moderate or strong, NOAA Administrator Neil Jacobs said Thursday.

Atlantic hurricane seasons when an El Nino reaches strong or very strong status have two-thirds the named storms and half the hurricanes of the 1991-2020 average, according to an Associated Press analysis of storm and El Nino statistics.

El Ninos fight Atlantic storm formation in several ways, especially with cross winds about 1 mile to 7 miles (1.5 to 11 kilometers) above the surface “which can basically blow apart the thunderstorms that make up” a hurricane, Corbosiero said.

“A stronger than normal wind shear tends to tilt storms as they try to develop,” said University at Albany atmospheric scientist Brian Tang. “It pushes dry air into storms. And prevents storms from developing in the first place. And if they do develop, it also prevents them from intensifying.”

Forecasts for peak hurricane season show strong wind shear from the west in the main development region for the largest and long-lasting hurricanes that come off of Africa and develop as they head west over the Atlantic, Klotzbach said. Fewer of these type storms happen during El Ninos.

In the 15 strongest El Nino years since 1950, 37 named storms, 11 hurricanes and three major hurricanes made landfall on the continental United States, but in the 15 coldest La Nina years 61 named storms, 31 hurricanes and 10 major hurricanes hit America's Gulf and Atlantic coasts, according to Klotzbach. He said El Nino shrinks the number of hits on the Atlantic coast, but has less of an influence on the number of Gulf coast landfalls.

Opposite effect in the Pacific

El Ninos and La Ninas have the opposite effect on storms in the central and eastern Pacific as they do in the Atlantic, so experts are expecting a busier season in those regions. Jacobs said there's a 70% chance that the eastern Pacific will have an above normal season.

Eastern Pacific storms near Baja Mexico tend to “go west affect the fishies and little else,” Corbosiero said. But at times they can turn east or north and cause massive damage as in Hurricane Otis in 2023 that smashed into Mexico, or 1992's Hurricane Lester, which caused heavy rains in the U.S. Southwest, she said.

Hawaii is a small island chain in a big ocean that can be threatened. In 1992, an El Nino year when there were few Atlantic storms (though Miami was devastated by Hurricane Andrew ), Hawaii was hit by Hurricane Iniki.

Further west toward Asia and India, “your odds of any storm forming becoming a super typhoon go up significantly in El Nino,” Klotzbach said.

The eastern Pacific hurricane season started May 15 and the Atlantic season begins June 1 and both end November 30.

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