A team of top researchers from Colorado State University anticipates another active Atlantic hurricane season for 2025, although their outlook is not as bullish as last year’s extremely busy summer and fall that spawned monster hurricanes like Helene and Milton.
Their forecast predicts 17 named storms and nine hurricanes, four of which are expected to reach “major” hurricane strength (Category 3 or higher) — just shy of last year’s hyperactive season that churned out 18 named storms, 11 hurricanes with five major hurricanes. That’s a lot more than the averages (for 1991-2020) of 14 storms, seven hurricanes, and three major hurricanes.
Along with NOAA’s annual forecast, expected to be released in May, CSU’s forecast is a closely watched gauge of upcoming hurricane activity during the Atlantic season, which runs from June 1 to Nov. 30. CSU’s forecast last year proved spot on.
This year, “the higher-than-average forecast is really a combination of warmer-than-average sea surface temperatures in key regions of the Atlantic and the expected lack of El Niño during the peak of the season,” said Levi Silvers, research scientist at CSU.
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El Niño typically creates a hostile environment for hurricanes to develop by increasing wind shear across the Caribbean and tropical Atlantic. Strong winds aloft can disrupt the vertical transport of air and moisture needed for storms to take shape.
“We expect, overall, more instances of favorable conditions for hurricanes to form this season,” Silvers said.
Researchers say it’s still way too early to predict a repeat of hurricane intensity that we saw last year with Helene and Milton, as well as the number of landfills, but the consensus is that there are greater chances for a major hurricane (Category 3 or greater strength) to form and strike land somewhere in the continental United States given that warm waters should only get warmer in the months ahead.
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The CSU outlook does predict higher odds of a major hurricane hitting the U.S. than usual: 51 percent. The odds of a landfalling hurricane striking the East Coast are 26 percent, compared to the typical 21 percent.
Sea surface temperatures
When forecasting for tropical cyclones, meteorologists not only look at sea surface temperatures to provide important clues, but they also study the equatorial trade winds and the presence of a La Niña or El Niño to provide insight. Forecasters also study previous seasons to help them form a clearer and more long-term picture.
Because hurricanes’ main fuel is warm water, ocean surface temperatures can dramatically impact how strong the winds are across the Atlantic and inhibit or promote storm development. Sea surface temperatures are currently running above average across the tropical Atlantic, though considerably cooler than the back-to-back record years of 2023 and 2024.
Despite the cooler water temperatures, the trade winds are expected to slow, meaning sea surface temperatures will warm up in the coming weeks.
Essentially, we still have more fuel than normal to support storm development, but not as much as we have seen in recent years.
El Niño and La Niña
El Niño and La Niña are the warm and cool phases of a naturally occurring climate pattern across the tropical eastern Pacific Ocean, off the west South American coast, that oscillates back and forth every two to seven years, greatly influencing and disrupting the weather across the U.S. and worldwide. They cause predictable shifts in ocean surface temperature. However, forecasters said the most probable phase for the hurricane season ahead is neither La Niña or El Niño. Models are pointing more toward “neutral conditions” that make the forecast more dependent on sea surface temperatures.
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“(Neutral conditions) can still produce active seasons, and we anticipate just that this season,” said Silvers.
A weak La Niña took hold in early December before waning.
There is a better chance for a La Niña to return by the tail end of hurricane season, but the overall chances remain low and may end up being a little too late to have much of an impact on the storms we see this season.
Meteorologists also lean on clues from the past to support what might occur in future hurricane seasons, and when you compare historical records that had similar meteorological factors in place, it’s called analog years.
CSU researchers found six years — 1996, 1999, 2006, 2008, 2011, and 2017 — each of which averaged about 14 named storms, eight hurricanes, and four major hurricanes. But this year, CSU is forecasting an increased number of named storms and hurricanes than the average from the analog years for two simple reasons — the air and ocean are both warmer.
The next CSU hurricane forecast update is scheduled for June 11. Globe Weather HQ will release its hurricane forecast in the coming weeks.
Ken Mahan can be reached at ken.mahan@globe.com. Follow him on Instagram @kenmahantheweatherman.