Something a bit unusual is happening in the tropics with less than a month to go before hurricane season
As the 2025 Atlantic hurricane season approaches, unusually cool sea surface temperatures, in the neighborhood of 2 °F below last year’s levels, are being observed across the Atlantic Ocean.
By Andrew Wulfeck
Colorado State University releases 2025 Atlantic hurricane season outlook
FOX Weather Hurricane Specialist Bryan Norcross discusses the first outlook issued for the 2025 Atlantic hurricane season, which was released Thursday morning by forecasters at Colorado State University. The CSU team is calling for 17 named storms, nine of which are expected to become hurricanes. Four of those hurricanes could reach major status, with winds of at least 111 mph (Category 3 or higher).
With the countdown underway for the start of the 2025 Atlantic hurricane season just one month away, there's an unusual sight unfolding in the tropics - one that hasn't been seen in several years.
Instead of news about the ocean breaking temperature records, a large part of the Main Development Region has experienced water temperatures trending downward.
In fact, the North Atlantic Ocean is approximately 2 degrees F cooler compared to this time last year, a factor that could significantly influence the development and intensity of tropical cyclones.
Water temperature anomalies in the Atlantic basin.
Water temperature anomalies in the Atlantic basin.
(Tropicaltidbits.com / FOX Weather)
According to a FOX Weather analysis, current ocean temperatures across the North Atlantic are comparable to values observed in 2019.
While temperatures are still warmer than long-term averages from 1982 to 2010 and 1991 to 2020, they mark a noticeable shift from recent seasons that featured record-breaking heat.
Interestingly, the 2019 hurricane season also occurred during a neutral status of the El Niño–Southern Oscillation, meaning that temperatures in critical parts of the Pacific Ocean were around average.
North Atlantic water temperatures compared to previous years.
North Atlantic water temperatures compared to previous years. 2025 is tracking well below 2024 levels.
(Climate Change Institute at the University of Maine / FOX Weather)
During the 2019 hurricane season, the Atlantic basin began the season with MDR values that were around average in June and July, but a significant warming trend in August and September helped fuel powerful hurricanes like Dorian and Humberto.
Dorian was the strongest hurricane on record to impact the Bahamas with winds around 185 mph and Humberto was a powerful Category 3 while off the mid-Atlantic coast.
2025 ATLANTIC HURRICANE SEASON GUIDE: HERE’S WHAT TO KNOW ABOUT THE TROPICS THIS YEAR
So, what’s driving the current cooling trend in the Atlantic?
One significant factor is the persistent Bermuda High, which has been fairly steadfast and centered northeast of the island nation of Bermuda.
The ridge has helped to strengthen easterly trade winds across the Atlantic, allowing for ocean upwelling and leading to a drop in sea surface temperatures.
Pressure anomalies showing a stout ridge in the Atlantic Ocean.
Pressure anomalies map showing a stout ridge in the Atlantic Ocean.
(NCEP / NOAA)
Evidence of a significant ridge has been all too apparent in Florida and the Southeast, where drier conditions have led to worsening drought conditions and an increase in wildfire activity.
The same easterly flow has also contributed to encounters with marine life washing ashore, including Portuguese man-of-war, and a rise in dangerous rip currents, which have already led to several fatalities this spring.
The big question now is: when will the ridge weaken and a pattern shift occur?
A breakdown in the Bermuda High would likely reduce the strength of the trade winds, allowing ocean temperatures to rebound. However, current short term do not suggest any imminent changes.
If the general pattern holds, the 2025 hurricane season may very well begin with large portions of the Atlantic basin featuring below-normal sea surface temperatures – a scenario that hasn’t happened in several years.
This could delay or even reduce early-season development, especially for disturbances emerging from the Cabo Verde region off the west coast of Africa.
It’s worth noting that despite cooler anomalies in parts of the Atlantic, other regions remain warm enough to support tropical cyclone formation.
The southern Gulf and the Caribbean Sea, for example, typically maintain water temperatures in the upper 70s or warmer year-round – waters that are warm enough to support tropical cyclone activity.
This map shows where tropical cyclone activity tends to occur during June. The data are shown as the combined number of tropical depressions, tropical storms and hurricanes whose centers pass within 125 miles of a point on the map during a 100-year period. The analysis is based on data from the 72-year period from 1950 to 2021 but normalized to 100 years.
This map shows where tropical cyclone activity tends to occur during June. The data are shown as the combined number of tropical depressions, tropical storms and hurricanes whose centers pass within 125 miles of a point on the map during a 100-year period. The analysis is based on data from the 72-year period from 1950 to 2021 but normalized to 100 years.
(FOX Weather)
HERE’S A FIRST LOOK AT HOW BUSY HURRICANE ACTIVITY COULD BE IN THE EASTERN PACIFIC
A look at what triggers early season activity
A common early-season catalyst is the Central American Gyre - a broad area of low pressure that often forms over the Americas in late spring and early summer.
The gyre can spawn tropical cyclones in either the eastern Pacific or western Atlantic basin, where water temperatures aren’t a limiting factor.
Once the gyre dissipates, typically by mid to late summer, meteorologists turn their attention eastward to the MDR for the possibility of tropical cyclone development.
Central American Gyre
Central American Gyre map explainer
(FOX Weather)
But if sea surface temperatures remain suppressed in the region, the season could feature a delayed ramp-up in significant tropical activity.
That said, weather patterns are known to shift rapidly - and sometimes without clear model guidance - so that is why forecasters encourage everyone in hurricane impact zones to prepare before the season arrives.
The first named storm of the 2025 Atlantic hurricane season will be Andrea, followed by Barry, Chantal and Dexter. The name Dexter replaces Dorian, which was retired after the 2019 season.
Maps and photos:
www.foxweather.com
As the 2025 Atlantic hurricane season approaches, unusually cool sea surface temperatures, in the neighborhood of 2 °F below last year’s levels, are being observed across the Atlantic Ocean.
By Andrew Wulfeck
Colorado State University releases 2025 Atlantic hurricane season outlook
FOX Weather Hurricane Specialist Bryan Norcross discusses the first outlook issued for the 2025 Atlantic hurricane season, which was released Thursday morning by forecasters at Colorado State University. The CSU team is calling for 17 named storms, nine of which are expected to become hurricanes. Four of those hurricanes could reach major status, with winds of at least 111 mph (Category 3 or higher).
With the countdown underway for the start of the 2025 Atlantic hurricane season just one month away, there's an unusual sight unfolding in the tropics - one that hasn't been seen in several years.
Instead of news about the ocean breaking temperature records, a large part of the Main Development Region has experienced water temperatures trending downward.
In fact, the North Atlantic Ocean is approximately 2 degrees F cooler compared to this time last year, a factor that could significantly influence the development and intensity of tropical cyclones.
Water temperature anomalies in the Atlantic basin.
Water temperature anomalies in the Atlantic basin.
(Tropicaltidbits.com / FOX Weather)
According to a FOX Weather analysis, current ocean temperatures across the North Atlantic are comparable to values observed in 2019.
While temperatures are still warmer than long-term averages from 1982 to 2010 and 1991 to 2020, they mark a noticeable shift from recent seasons that featured record-breaking heat.
Interestingly, the 2019 hurricane season also occurred during a neutral status of the El Niño–Southern Oscillation, meaning that temperatures in critical parts of the Pacific Ocean were around average.
North Atlantic water temperatures compared to previous years.
North Atlantic water temperatures compared to previous years. 2025 is tracking well below 2024 levels.
(Climate Change Institute at the University of Maine / FOX Weather)
During the 2019 hurricane season, the Atlantic basin began the season with MDR values that were around average in June and July, but a significant warming trend in August and September helped fuel powerful hurricanes like Dorian and Humberto.
Dorian was the strongest hurricane on record to impact the Bahamas with winds around 185 mph and Humberto was a powerful Category 3 while off the mid-Atlantic coast.
2025 ATLANTIC HURRICANE SEASON GUIDE: HERE’S WHAT TO KNOW ABOUT THE TROPICS THIS YEAR
So, what’s driving the current cooling trend in the Atlantic?
One significant factor is the persistent Bermuda High, which has been fairly steadfast and centered northeast of the island nation of Bermuda.
The ridge has helped to strengthen easterly trade winds across the Atlantic, allowing for ocean upwelling and leading to a drop in sea surface temperatures.
Pressure anomalies showing a stout ridge in the Atlantic Ocean.
Pressure anomalies map showing a stout ridge in the Atlantic Ocean.
(NCEP / NOAA)
Evidence of a significant ridge has been all too apparent in Florida and the Southeast, where drier conditions have led to worsening drought conditions and an increase in wildfire activity.
The same easterly flow has also contributed to encounters with marine life washing ashore, including Portuguese man-of-war, and a rise in dangerous rip currents, which have already led to several fatalities this spring.
The big question now is: when will the ridge weaken and a pattern shift occur?
A breakdown in the Bermuda High would likely reduce the strength of the trade winds, allowing ocean temperatures to rebound. However, current short term do not suggest any imminent changes.
If the general pattern holds, the 2025 hurricane season may very well begin with large portions of the Atlantic basin featuring below-normal sea surface temperatures – a scenario that hasn’t happened in several years.
This could delay or even reduce early-season development, especially for disturbances emerging from the Cabo Verde region off the west coast of Africa.
It’s worth noting that despite cooler anomalies in parts of the Atlantic, other regions remain warm enough to support tropical cyclone formation.
The southern Gulf and the Caribbean Sea, for example, typically maintain water temperatures in the upper 70s or warmer year-round – waters that are warm enough to support tropical cyclone activity.
This map shows where tropical cyclone activity tends to occur during June. The data are shown as the combined number of tropical depressions, tropical storms and hurricanes whose centers pass within 125 miles of a point on the map during a 100-year period. The analysis is based on data from the 72-year period from 1950 to 2021 but normalized to 100 years.
This map shows where tropical cyclone activity tends to occur during June. The data are shown as the combined number of tropical depressions, tropical storms and hurricanes whose centers pass within 125 miles of a point on the map during a 100-year period. The analysis is based on data from the 72-year period from 1950 to 2021 but normalized to 100 years.
(FOX Weather)
HERE’S A FIRST LOOK AT HOW BUSY HURRICANE ACTIVITY COULD BE IN THE EASTERN PACIFIC
A look at what triggers early season activity
A common early-season catalyst is the Central American Gyre - a broad area of low pressure that often forms over the Americas in late spring and early summer.
The gyre can spawn tropical cyclones in either the eastern Pacific or western Atlantic basin, where water temperatures aren’t a limiting factor.
Once the gyre dissipates, typically by mid to late summer, meteorologists turn their attention eastward to the MDR for the possibility of tropical cyclone development.
Central American Gyre
Central American Gyre map explainer
(FOX Weather)
But if sea surface temperatures remain suppressed in the region, the season could feature a delayed ramp-up in significant tropical activity.
That said, weather patterns are known to shift rapidly - and sometimes without clear model guidance - so that is why forecasters encourage everyone in hurricane impact zones to prepare before the season arrives.
The first named storm of the 2025 Atlantic hurricane season will be Andrea, followed by Barry, Chantal and Dexter. The name Dexter replaces Dorian, which was retired after the 2019 season.
Maps and photos:
Something a bit unusual is happening in the tropics with less than a month to go before hurricane season
As the 2025 Atlantic hurricane season approaches, unusually cool sea surface temperatures, in the neighborhood of 2 °F below last year’s levels, are being observed across the Atlantic Ocean.
www.foxweather.com
