So, what can we expect for this year’s Atlantic hurricane season? All signs point towards an average or slightly below-average season, but with the chance for slightly more major hurricanes than usual.
The early Globe Weather HQ forecast shows 12 to 15 named storms and four to six hurricanes, three or four of which become major, meaning Category 3 strength or stronger.
That would be roughly in line with the seasonal average — 14 named storms, seven hurricanes, and three major hurricanes. But it’s worth highlighting the potential for more major hurricanes than usual.
Globe Weather HQ’s early forecast shows a near-normal hurricane season.Boston Globe
El Niño emerges while sea surface temperatures are closer to average
There are two major components contributing to the forecast — the first is high confidence in a bona fide El Niño pattern firming up by summer, which is a natural hurricane suppressor in the Atlantic.
The second? Sea surface temperatures across the area where most hurricanes form, called the Main Development Region (MDR), are basically at the 30-year average.
You may already know this, but El Niño and La Niña are the warm and cool phases of a recurring climate pattern that occurs every few years across the tropical eastern Pacific, and has a great impact on weather patterns worldwide.
El Niño is the warming of sea surface temperatures above normal, which causes more storms to develop in the Pacific. This means winds will ramp up in the upper levels of the atmosphere when cycling back toward the Atlantic. This process increases the wind speed of sinking air over the Atlantic, which makes it very difficult for tropical thunderstorms to form.
Three phases of the tropical Pacific atmospheric circulation pattern: El Niño, La Niña, and neutral. During El Niño, the engine driving tropical circulation creates more storms over the Pacific, with less storm formation over the Atlantic from sinking air. NOAA
“Most models are pretty aggressive at El Niño emerging,” said Phil Klotzbach, senior research scientist at Colorado State University. “Some models are pointing towards a 2-degree increase in sea surface temperatures across the Pacific, meaning Super El Niño, which would likely really knock down Atlantic hurricane activity downstream.” The warmer the equatorial Pacific gets, the cooler the tropical Atlantic typically remains.
Honestly, the models keep flipping on whether or not we reach a super El Niño, but given the historical odds, I doubt the seas will warm up that dramatically over the Equatorial Pacific.
The last super El Niño occurred in 2015-2016 when sea temperatures peaked at 2.6 degrees above normal. Only two other El Niños broke the 2-degree threshold: 1997-98 and 1982-83. (Records date back to 1950.)
In 2015, there were 11 named storms and four hurricanes, two of which became major storms, below the usual amount.
Tropical activity changes during an El Niño event. The Atlantic usually sees fewer storms.Boston Globe
You can see below the probability of El Niño (red bar) developing by the May-June-July time frame, and remaining in place for the rest of the year.
El Niño will likely emerge during the summer and likely remain through the rest of the year.IRI
In terms of sea surface temperatures, we’ve seen the MDR run well above-average in previous years. However, heading into April, ocean temperatures across the tropical zone where most tropical storms form sit just at the climatological norm, which simply means that the seas have been cooler at this point in the year versus the last few years.
For instance, the MDR is currently about a third of a degree cooler than last year and more than a full degree cooler than 2024. And what happens to sea surface temperatures across the Atlantic during an El Niño? Ocean surfaces warm less efficiently due to stronger winds mixing cooler water up from below. And we know that tropical storms and hurricanes need warmer seas to thrive.
Sea surface temperatures across the Main Development Region are just about average.Boston Globe
El Niño seasons still produce powerhouse hurricanes
Even though the odds are stacked against a blockbuster hurricane season, destructive storms are still more than possible.
Our most recent El Niño hurricane season in 2023 saw sea surface temperatures soar despite the influence of the climate pattern, resulting in 20 named storms. This scenario is highly unusual, but it proves that storms can emerge if localized conditions are right.
In 2018, we saw a moderate El Niño, but Hurricane Michael grew into a Category 5 monster, making landfall over the Florida panhandle. We saw Hurricane Andrew wreak havoc during an El Niño year, too.
Remember Hurricane Bob? The last hurricane to make landfall in New England was in 1991, which also happened to be a strong El Niño year.
I’m not saying that’ll happen this year, but it’s certainly worth noting.
Ken Mahan can be reached at [email protected]. Follow him on Instagram @kenmahantheweatherman.
