55% chance of a below-average hurricane season ... NOAA forecasts milder-than-normal period thanks to El Niño

A developing El Niño that is forecast to become quite strong will likely dampen the upcoming Atlantic hurricane season, but it will not make the potentially deadly storms disappear, federal and independent meteorologists predict.

The National Oceanic and Atmospheric Administration (NOAA) last week issued its seasonal outlook for the Atlantic, giving a 55 per cent chance of a below-average season.

It forecasts eight to 14 named storms, with three to six of them becoming strong enough to reach hurricane status, and one to three of those intensifying into major hurricanes.

A normal hurricane season has 14 named storms, seven of them becoming hurricanes and three of them reaching major hurricane status, defined as more than 110 mph (177 kph).

Eighteen other groups, both private and academic, have also issued forecasts for the season, and most of them also call for a below-average summer and autumn. These other forecasts average a dozen named storms, with only five becoming hurricanes and two of those being major ones. They also predict the Accumulated Cyclone Energy index — which takes into account the strength and duration of storms — will be 80 per cent of normal.

Colorado State University, which pioneered the science of seasonal hurricane forecasting in 1984, is predicting the lowest overall activity since 2015, which saw the strongest El Niño in the past 75 years. That forecast is likely to be revised to even lower numbers in June, said Colorado State’s hurricane expert Phil Klotzbach.

This follows nine of the last 10 Atlantic hurricane seasons being above normal or even hyperactive, Klotzbach said.

NEAR-RECORD TOTAL

Last year started slowly but then intensified, 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 worldwide from tropical cyclones has increased from an average of US$11.4 billion a year in the 1980s to $109.7 billion a year over the past 10 years, with three-quarters of the damage occurring in the Atlantic, Gulf of Mexico and Caribbean, according to insurance giant Munich Re.

Hurricanes, typhoons and cyclones refer to the same weather phenomenon, with different names used in different parts of the world.

“We should expect a less active year than certainly what we’ve seen recently, and perhaps significantly 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 US or even in Hawaii.”

It is largely because of “the elephant in the room”, which is an El Niño, Camargo said.

An El Niño is the natural, cyclical warming of parts of the central Pacific that alters weather patterns around the globe, especially during winter. Scientists have for decades found a correlation between an El Niño and below-average Atlantic hurricane activity, alongside stronger and more frequent storms in the central and eastern Pacific. This year, many forecasts are calling for a strong, super-strong or even record-setting El Niño. During a La Niña, the cooler counterpart to El Niño, the Atlantic is generally more active, with stronger storms.

There is a 98 per cent chance that there will be an El Niño this summer and an 80 per cent chance it will be moderate or strong, NOAA Administrator Neil Jacobs said.

Atlantic hurricane seasons during strong or very strong El Niño events typically have two-thirds the number of named storms and half the number of hurricanes compared with the 1991–2020 average, according to an AP analysis of storm and El Niño data.

El Niños hinder Atlantic storm formation in several ways, particularly through crosswinds at altitudes of about one to seven miles (1.5 to 11 kilometres), “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 them from developing in the first place. And if they do develop, it also prevents them from intensifying.”

El Niño reduces the number and intensity of weaker storms, but once a storm reaches hurricane status, with winds of 74 mph, “they can be kind of like a self-feeding entity” and are less affected by El Niño’s wind shear, said Matthew Rosencrans, lead hurricane season forecaster with NOAA’s National Weather Service.

Forecasts for peak hurricane season show strong wind shear from the west in the main development region for large, long-lived hurricanes that form off Africa and move westwards across the Atlantic, Klotzbach said. Fewer of these types of storms occur during El Niño events.

In the 15 strongest El Niño years since 1950, 37 named storms, 11 hurricanes and three major hurricanes made landfall on the continental United States. By contrast, in the 15 coldest La Niña years, 61 named storms, 31 hurricanes and 10 major hurricanes struck the US Gulf and Atlantic coasts, according to Klotzbach. He said El Niño reduces the number of Atlantic coast landfalls but has less influence on Gulf coast impacts.

In addition to El Niño, dry conditions in Africa and sea-surface temperatures in the Atlantic being only slightly above normal also contribute to the forecast of a weaker season, Rosencrans said.

OPPOSITE EFFECTS

El Niños and La Niñas have the opposite effect on storms in the central and eastern Pacific compared with the Atlantic, so experts are expecting a busier season in those regions. Jacobs said there is a 70 per cent chance the eastern Pacific will experience an above-normal season.

NOAA forecasts 15 to 22 named storms in the Pacific, with nine to 14 becoming hurricanes and five to nine of those reaching major hurricane status. The average is 15 named storms, eight hurricanes and four major hurricanes. Rosencrans said the main area of central Pacific storm development shifts closer to Hawaii during El Niño events.

Eastern Pacific storms near Baja Mexico tend to “go west, affect the fish and little else,” Corbosiero said. However, they can sometimes turn east or north and cause significant damage, as in Hurricane Otis in 2023, which struck Mexico, or Hurricane Lester in 1992, which caused heavy rainfall in the south-western US, she added.

Hawaii, a small island chain in a vast ocean, remains vulnerable. In 1992, an El Niño year with few Atlantic storms (although Miami was devastated by Hurricane Andrew), Hawaii was struck by Hurricane Iniki.

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

The eastern Pacific hurricane season began on May 15, while the Atlantic season starts on June 1. Both run until November 30.

El Niños can also prolong the hurricane season, said John Bravender, a meteorologist with the weather service in Honolulu. “With the warmer waters across the area, not only can hurricanes maintain their strength at higher latitudes, but also longer through the year,” he said.

The state is preparing for hurricanes as parts of Hawaii continue to recover from recent back-to-back storms that caused catastrophic flooding, Governor Josh Green said.

- AP

File name: Santa Cruz Melissa

Caption: Residents walk through Santa Cruz, Jamaica, on October 29 after Hurricane Melissa passed. AP photos

File name: Philippines thyphoon

Caption: A woman and child cross a flooded street due to Typhoon Fung-wong and high tide on November 10 in Navotas, Philippines.

File name: Melissa prep Kingston

Caption: Men remove a loose section of roof in Kingston, Jamaica, as Hurricane Melissa approaches on October 28.