How El Nino is shaping tropical storms worldwide

None of the six tropical storms registered in the Atlantic so far this year have reached hurricane status (FILE photo of Hurricane Matthew in Oct. 2016) – Image: Tim Aylen/AP Photo/picture alliance

From drought to major floods and extreme heat, El Nino will have a huge impact on the world’s weather. In the Atlantic, it could mean a season without hurricanes.

In a typical year, storm watchers have logged several hurricanes by late September. At this point in 2005, one of the most active years on record, five major hurricanes had already churned their way through the Atlantic Ocean — including Katrina, one of the most devastating in US history.

But 2026 has been quiet so far. As of September 23, only six tropical storms had formed over the North Atlantic, and none had intensified into hurricanes — a first since satellites began tracking storms in 1966, according to the National Oceanic and Atmospheric Administration (NOAA) in the US.

“In the satellite era, we have never had a year without a hurricane,” said Matthew Rosencrans, lead hurricane season forecaster with NOAA’s Climate Prediction Center. “This would be a first.”

That’s due, in large part, to the latest iteration of the El Nino-Southern Oscillation (ENSO), a shifting cycle of winds and sea surface temperatures over the Pacific Ocean that shapes weather worldwide and makes it a “dominant factor in total hurricane season activity.” Meteorologists have said this year’s El Nino could be one of the strongest on record.

Hurricane Katrina, in August 2005, claimed some 1,200 lives and left New Orleans underwater for weeks – Image: Gary Coronado/Palm Beach Post/dpa/picture alliance

Hurricane, typhoon, cyclone — what’s the difference?

NOAA’s Climate Prediction Center, which tracks Atlantic storm data in the US, said the accumulated cyclone energy of this year’s tropical storms — a calculation that factors in storm duration and intensity — was at a record low for so late in the season, which typically peaks on September 10.

None of the six tropical storms registered so far have reached a wind speed of at least 119 kilometers per hour (74 miles per hour) — strong enough to be considered a Category 1 hurricane with the potential to cause some minor damage to homes, trees and other infrastructure.

The name for such a catastrophic tropical storm is regional. What’s known as a hurricane in the North Atlantic and eastern Pacific will be called a typhoon on the other side of the Pacific, in eastern Asia. In the Indian Ocean and the South Pacific, meteorologists will generally classify a similar storm as a cyclone.

How does El Nino affect Atlantic hurricanes?

NOAA’s latest data showed that El Nino is still strengthening, with sea surface temperature rise in the key Pacific region now exceeding 3 degrees Celsius (5.4 Fahrenheit), creating a “very strong” El Nino over the next half year — and a “below-normal” hurricane season.

Almost all Atlantic tropical cyclone activity occurs between June 1 and November 30, though hurricanes can form at other times of the year. And meteorologists have warned that this year’s calm doesn’t rule out a major hurricane before the season is done.

The naturally occurring El Nino weather pattern returns on average every two to seven years, with its effects lasting up to a year. During El Nino, the regular trade winds moving east-west across the Pacific weaken and sometimes even reverse. The changes in humidity and wind shift the jet stream, the strong winds in the upper atmosphere — and disrupt storm formation in the Atlantic.

NOAA’s Climate Prediction Center said any hurricanes that do appear in an El Nino year tend to form along the US East Coast and near the Gulf of Mexico, giving them less time to turn into major hurricanes — but also leaving coastal communities with less time to prepare. That pattern is largely dictated by the steering currents when it forms, which typically last around a week.

“Formations deep in the tropics are hampered due to high wind shear,” said Rosencrans — the strong changes in wind speed or direction at different altitudes are more likely to disrupt storm formation. “The stronger the El Nino event, the stronger the wind shear.”

Pacific typhoons change track, head north

During El Nino, vertical wind shear isn’t as strong in the eastern and central Pacific Ocean. Combined with the warmer waters in the Pacific, which fuel storms with heat and moisture, that tends to result in an increase in tropical cyclones in this region. This part of the Pacific has already seen several major hurricanes this year, including Polo, which this week has grown into one of the most powerful Pacific cyclones in decades — fueled in part by El Nino.

“Typically, El Nino means the storms form further east […] toward the international date line and Marshall Islands,” Rosencrans told DW, anticipating an “above average” hurricane season in the Pacific. “This does mean that storms have longer life spans before reaching large land masses.”

Anne-Claire Fontan at the World Meteorological Organization said during an El Nino event, storms on the Asian side of the vast Pacific tend to track “northward, rather than continue westwards towards East and Southeast Asia.”

That meant, according to Rosencrans, that Guam, the Northern Mariana Islands, Japan and the Korean Peninsula “can face slightly higher odds of tropical storms and typhoons.”

The eastern Pacific off the Americas has been especially active this season, with four hurricanes in the last month -Image: CIRA/NOAA/AP Photo/picture alliance

Strong El Nino also disrupts storms in Indian Ocean

A strong El Nino will weaken monsoon winds over the Indian subcontinent, often triggering severe drought. It also generally corresponds with a less active tropical cyclone season in the Indian Ocean, said Fontan, a scientific officer with the WMO’s Tropical Cyclone Program.

Much like in the Atlantic, increased wind shear in this region can disrupt or delay the formation of storms, which Fontan said lessened the risks for countries in eastern Africa, like Madagascar and Mozambique.

“In terms of overall tropical cyclone activity in the Southwest Indian Ocean, there is a non-linear, or ‘bell-shaped,’ relationship with ENSO,” said Fontan, highlighting El Nino and its opposite phase. “As ENSO moves towards either of its extremes — a strong El Nino or a strong La Nina — tropical cyclone activity in the basin tends to be below normal.”

Are El Nino and climate change linked?

The El Nino-Southern Oscillation is a natural phenomenon, and not caused by climate change. And, as Rosencrans pointed out, “the interplay of El Nino or La Nina and the longer-lived changes is just one piece of what makes hurricane seasons active or inactive.”

Among those factors is the dry, dusty air drifting out over the Atlantic from the Sahara Desert, which can also suppress hurricanes.

But Fontan said that the especially strong El Nino effect, combined with the warming effects of climate change from burning fossil fuels, is setting the stage for unprecedented weather extremes in the months ahead.

“El Nino is occurring in a warmer world, and this can amplify some of its impacts, including extreme heat, heavy rainfall and drought,” she told DW. Already, some forecasters like the UK’s Met Office have said the combined effects of El Nino and climate change could shatter heat records in 2027. A new report from the University of Chicago-based Climate Impact Lab has projected that extreme heat could cause nearly half a million more deaths worldwide during this El Nino period, especially in the Global South.

“We are already seeing the disruption and devastation caused by droughts and floods, and we expect these impacts to worsen as El Nino intensifies,” said Celeste Saulo, head of WMO, in early September, in a stark warning for governments and humanitarian organizations.

DW.com/NAN 24-09-26

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