JACKSONVILLE, FL – A dramatic sea surface temperature change occurred, the likes of which has never been seen before in parts of the Atlantic, which could alter the outcome of a season of extreme hurricanes.

Since March 2023, sea surface temperatures have been at record highs across the North Atlantic. The temperatures were so extreme that large parts of the North Atlantic were affected by a marine heat wave.

In early 2024, the eastern equatorial part of the Atlantic experienced an unprecedented heatwave. From February to March, sea temperatures rose above 30 °C, making it the hottest period since 1982. But what was striking was how quickly things changed: the sea went from unusually hot to unusually cold in record time.

The cooling has continued. Since early June, sea surface temperatures (SST) in the central equatorial Atlantic have been 0.9–1.8 degrees Fahrenheit below normal for this time of year. If these cooler conditions continue through late August, we could see the declaration of a phenomenon called the “Atlantic Niña.”

What is an Atlantic Nina?

The term “Atlantic Nina” refers to a climate pattern characterized by below-average sea surface temperatures in the tropical Atlantic.

This is not to be confused with the Pacific La Niña phenomenon, which also contributes to below-average sea surface temperatures in the central and eastern tropical Pacific.

The Pacific variant typically leads to altered weather patterns on a global scale, while the Atlantic Nina variant is more localized and its effects are more directly related to changes in hurricane activity in the Atlantic.

The Atlantic Ocean’s cool pool of water is usually formed when southeasterly winds blow into a band of persistent clouds in the Intertropical Convergence Zone. The winds blowing across the ocean stir it up in a way that draws deeper, cooler water to the surface.

However, meteorologists are puzzled as to how this recent cooling could have occurred, even though the southeast trade winds are generally weaker near the equator, which is normally associated with reduced buoyancy and heat anomalies.

Water temperatures in the main hurricane development area in the Atlantic are still warmer than average, so it’s unknown how the cool pool might affect the rest of the hurricane season. At least for now, and possibly through the end of August, conditions appear to be very calm for storm development.