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As Tropical Storm Bertha continues to spin along the Gulf Coast on July 22, powerful upper-level winds are ripping the system apart and keeping it much weaker than it might otherwise be.
The upper-level winds, known as wind shear, plaguing Bertha could be a harbinger of what we can expect for the remainder of the 2026 Atlantic hurricane season, one that is set to be strongly influenced by a powerful El Niño.
Wind shear is "the number one calling card of El Niño," Michael Lowry, a Miami-based hurricane expert with WPLG-TV, told CNN.
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According to Lowry, El Niño’s most prominent mark on the hurricane season is to ratchet up vertical wind shear – the scissor-like wind pattern that lops off the tops of organizing storm seedlings before they can develop into strong hurricanes.
However, these specific winds over the Gulf haven't been directly linked to a El Niño. And there's some evidence this particular weather pattern isn't directly connected.
El Niño tends to impact winds over the Caribbean Sea and the tropical Atlantic Ocean, but not necessarily the Gulf.
"I think it's a bit difficult to tie in the stronger shear that Bertha is currently experiencing to El Niño," said Colorado State University hurricane researcher Phil Klotzbach in an email to USA TODAY. "That's because El Niño tends to have its strongest shear impacts at lower latitudes (for example, the Caribbean or the tropical Atlantic).
"The driver of the strong shear that Bertha is currently experiencing is high pressure in the Midwest," he said. "The circulation around that high-pressure system is causing strong northeasterly shear over Bertha."
What is wind shear?
Wind shear describes the changes in wind direction or speed between different levels of the atmosphere, said CNN meteorologist Mary Gilbert in an online report.
"It can tear apart tropical systems or prevent them from forming in the first place — and it's established a firm grip over the Caribbean Sea and the western Atlantic Ocean," Gilbert noted earlier this week. "June and July are typically the quietest months of the season, but this shear has been a major roadblock and could have implications for the peak months, too," she added.
Where does El Niño fit in?
How does El Niño — a natural warming of tropical Pacific sea water — cause wind shear over the Atlantic? First, El Niño warms the Pacific, which changes global atmospheric circulation patterns, according to the National Oceanic and Atmospheric Administration (NOAA). Those changes strengthen upper-level winds over the Caribbean and tropical Atlantic, increasing wind shear.
NOAA said that hurricanes thrive when the atmosphere is relatively calm all the way from the surface to the upper levels.
Strong wind shear tilts the nascent storm, disrupts its core and interferes with the upward transport of heat and moisture that fuels tropical storms and hurricanes. As a result, due to wind shear from El Niño, developing tropical disturbances are more likely to weaken, fail to organize, or struggle to intensify into major hurricanes, NOAA reports.
El Niño's impact is earlier than usual
Typically, however, it takes a little time for the abnormal warming of the waters in the eastern Pacific – the ocean phenomenon that defines El Niño – to link arms with the atmosphere and change global circulation patterns that ultimately reshape winds over the tropical Atlantic, Lowry said.
"This year, however, it appears we’re seeing that atmospheric feedback to the strengthening El Niño earlier than usual, which could be a result of the record-setting pace of the warming so far in the eastern equatorial Pacific," Lowry said in an e-mail to USA TODAY
The increase in wind shear is highest in the western part of the tropical Atlantic, especially across the Caribbean, which also helps to reduce the number of U.S. landfalls during El Niño years.
Quiet season expected due to El Niño's impacts
Forecasts for the 2026 Atlantic hurricane season were mostly below-normal due to the storm-snuffing impacts of El Niño. For example, Colorado State University, in a recent forecast, said that only nine named storms would form, well below the average of 14.
What's next for hurricane season?
Klotzbach added that predicted ongoing strong wind shear over the Caribbean and Atlantic will likely continue to quash hurricanes before they can develop.
"Vertical wind shear is currently running even higher than we typically see in below-average Atlantic hurricane seasons," he said. "As you might expect given the strong El Niño that is now underway, the latest four-week forecast from [the European weather model] ECMWF indicates well above-normal shear is likely across the Caribbean and tropical Atlantic over the next few weeks."
Doyle Rice is a national correspondent for USA TODAY, with a focus on weather and climate.
This article originally appeared on USA TODAY: A powerful force is tearing Bertha apart. It's a hallmark of El Niño
