The brutal heat of May has felt like August in Florida, with heat index numbers topping highs that you’d normally expect at summer’s peak. The phenomenon is occurring at sea, too, and that’s bad news for hurricane season.
Sea-surface temperatures in the Atlantic Ocean, particularly in the Main Development Region for hurricanes, an area that runs from the west coast of Africa to the Gulf of Mexico, are 2.5 months ahead of schedule. The area is currently as hot as it normally is in August (2013-2023 average).
“On May 20, the ocean heat content in the Main Development Region (MDR) of the Atlantic is now where it normally would be on Aug. 10,” wrote University of Miami Climatologist Brian McNoldy on X.
Tropics check:
On May 20, the ocean heat content in the Main Development Region (MDR) of the Atlantic is now where it normally would be on August 10. 💣https://t.co/CdrzWVvKiZhttps://t.co/Id3wcCr25r pic.twitter.com/I6vjS67cSZ— Brian McNoldy (@BMcNoldy) May 20, 2024
The early warming has sparked concern among meteorologists.
Warm waters fuel hurricanes, and this season is expected to already be an active one due to a pending La Niña.
The result of all this hot-water? Predictions of a very strong hurricane season by both the University of Colorado and the National Oceanic and Atmospheric Administration.
NOAA has forecast:
- 17 to 25 named tropical storms for 2024 with minimum sustained winds of 39 mph. The average is 14.
- Eight to 13 hurricanes with sustained wind speeds of at least 74 mph. The average year has seven.
- Four to seven major hurricanes with sustained winds over 111 mph. The average is three.
Is 2024 all that special? McNoldy thinks so.
“You have a background increase (in sea-surface temperature) due to global warming. … That said, things really kinda got out of control in the spring of 2023, and they’re still going out of control. 2024 is way above 2023. We’re at more than a year now of blowing past records by giant margins.”
Why is the ocean so hot? Scientists have some ideas, but none can fully account for the current temperatures.
One factor, ironically, may be the reduction of sulfur dioxide pollution in the shipping industry due to global pollution standards set in 2020.
The pollution particles actually block sunlight, and now more solar radiation can reach the oceans.
Another possible factor is the underwater eruption of Hunga Tonga-Hunga Haʻapai volcano in 2022 near Tonga in the Pacific Ocean.
Underwater eruptions can send vast amounts of water vapor into the atmosphere, which then acts as a greenhouse gas.
Of the ship pollution and volcano theories, McNoldy said they could both be factors, but he’s not sold yet on the volcano’s effects.
It’s not just the Atlantic.
In March, the average global sea surface temperature hit 69.93 degrees F, a new record, according to Copernicus Climate Change Service, a research institution funded by the European Union.
Where’s the wind?
Wind keeps the ocean choppy, but when it’s smooth, it can absorb more heat.
McNoldy said a lack of wind is what really set things off in 2023.
“The Subtropical High (aka Bermuda High and Azores High) was a lot weaker than normal,” he said.
That did two things: It reduced the strength of the trade winds across the tropical Atlantic, and it reduced the Saharan dust outbreaks.
Saharan dust typically plumes out over the Atlantic from North Africa each summer, sometimes even reaching South Florida, resulting in hazy days and brilliant orange sunsets.
Those plumes also absorb some of the sun’s energy, and the dry desert air can stifle storms.
McNoldy said that this year, the Subtropical High is still weaker than normal, but not as weak as it was in 2023.
It’s also a bit of a double-edged sword. When it’s weak, hurricanes crossing the Atlantic tend to arc north and away from Florida earlier.
The Main Development Region isn’t just hot on the surface. Warm temperatures extend down.
Deep heat
The Ocean Heat Content measures the warmth of the ocean to a depth.
At the University of Miami, researchers measure the heat energy from the surface down to whatever depth the water temperatures tapers to 78.8 degrees F.(The temperature needed to produce hurricanes).
If that 78 degree line is relatively deep, and a high proportion of that water column is quite hot, the heat content is high.
In short, said McNoldy, “there’s more meat there than just the sea surface temperature.”
He said 2023 Ocean Heat Content in the Atlantic was record-breaking, and 2024 is well above that.
“It’s really strange to be seeing this, but it’s what we’re seeing.”
It would be pretty hard for water temperatures to cool with the sun as high as it is at this time of year, McNoldy said.
