JACKSONVILLE, FL – A dramatic flip-flop in sea surface temperature that had never been seen before in part of the Atlantic Ocean has developed which may change the outcome of what was expected to be a hyperactive hurricane season.
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Sea surface temperatures have been record-warm across the North Atlantic Ocean since March 2023. Temperatures have been so extreme that much of the North Atlantic has been experiencing a marine heatwave.
At the start of 2024, the part of the Atlantic in the eastern equatorial ocean experienced a heat wave like no other. From February to March, sea temperatures soared above 86°F, making it the hottest stretch since 1982. But what stood out was how quickly things changed: the sea went from unusually hot to unusually cold in record time.
The chill down has stuck around. Since early June, sea surface temperatures (SST) in the central equatorial Atlantic have been 0.9–1.8 degrees fahrenheit below the usual levels for this time of year. If these cooler conditions continue through the end of August, we might see the declaration of a phenomenon called Atlantic Niña.
What is an Atlantic Niña?
The term “Atlantic Niña” refers to a climate pattern characterized by cooler-than-average sea surface temperatures in the tropical Atlantic Ocean.
This is not to be confused with Pacific La Niña which also contributes to cooler-than-average sea surface temperatures in the central and eastern tropical Pacific Ocean.
The Pacific version typically leads to altered weather patterns globally, while the Atlantic Nina in contrast, is more localized, with its effects more directly linked to changes in Atlantic hurricane activity.
The Atlantic cool pool of water typically develops when southeasterly winds flow into a band of persistent clouds in the intertropical convergence zone. The winds blowing over the ocean stir it up in a way that draws deeper cooler water to the surface.
But meteorologists are perplexed about how this recent cool-down developed in overall weaker southeasterly trade winds near the equator which typically associated with reduced upwelling and warm anomalies.
Water temperatures in the hurricane main development region of the Atlantic are still hotter than average so it is unknown how the cool pool could impact the remainder of the hurricane season. At least for now and possibly through the end of August conditions for storm development are appearing very quiet.