Why this year’s weather helped Hurricane Beryl break records

Beryl’s fury is the superheated waters of the North Atlantic Ocean. Multiple teams of scientists have predicted that the 2024 Atlantic hurricane season would be «hyperactive» as a result of that record ocean heat, as well as the pending onset of the La Niña phase of the El Niño-Southern Oscillation, or ENSO, climate. pattern (SN: 29.4.24).

Predicted or not, scientists are still concerned about the stunning satellite images of Beryl and the speed with which the storm gained strength, says Brian McNoldy, an atmospheric scientist at the University of Miami. Scientific news spoke with McNoldy about hurricanes, ocean heat and what to expect for the rest of the Atlantic season. This interview has been edited for length and clarity.

SN: I’m looking at these satellite images and this ocean temperature data and I’m stunned.

McNoldy: Anyone who has seen these things is amazed. It’s just off the charts, for being late June-early July, and the ocean has more heat content than it would have at the height of hurricane season! And we are far from the peak.

SN: So let’s talk about ocean heat. We knew, even last year, that 2024 was likely to break records. What are we seeing now?

McNoldy: This year, the entire tropical Atlantic has been warmer than average, both in terms of sea surface temperatures and ocean heat content. In terms of ocean heat content—if we’re just zooming in on the Caribbean, which is the relevant part for this hurricane—it’s easily on a record. Ocean heat content now looks more like usual in the second week of September, [at the peak of the Atlantic hurricane season].

Getting hotter

The area of ​​the North Atlantic Ocean where most of its hurricanes form, known as the «core development region» (see inset map), was filled with superheated waters to fuel powerful storms even before Beryl began to organize. . The region’s ocean heat content—a measure not only of temperature at the ocean’s surface, but deeper in the water column—was higher than ever measured in 2024 (dark red line), even surpassing 2023 (lighter red line), which was the previous record holder. The average ocean heat content for the main development region from 2013 to 2023 is shown in blue.

Heat content of the Atlantic Ocean

SN: What is the difference between sea surface temperature and ocean heat content?

McNoldy: Sea surface temperature is nice and self-explanatory – it’s just the temperature right at the surface of the ocean. The heat content of the ocean is a measure of how deep that warm water goes. It can be measured in several different ways. The data I am processing [to analyze ocean heat trends] calculates ocean heat content based on temperatures that are 26° Celsius or higher. This is a very tropical cyclone oriented number – generally we think hurricanes are able to form and sustain themselves [with water temperatures at] 26°C or above. If the warm water is only skin deep, the heat content of the ocean is very, very small. But if the warm water goes much deeper, the heat content of the ocean is huge.

SN: Why does ocean heat content matter to hurricanes?

McNoldy: For storms like Beryl, very strong storms, if it moved over a part of the ocean where warm water was deep, it would easily bring cooler water to the surface, [which can reduce its intensity]. It will also leave a cooler wake in its wake. But in this case, I doubt we’ll see much of a cold wake, because the warm water is so deep that it’s just going to pump out more warm water. The hot waters probably descend to a depth of about 100 to 125 meters. So it doesn’t go anywhere. Storms don’t even pump out water that deep. It’s pretty crazy.

SN: Last year we were also seeing record heat. What’s different this year?

McNoldy: Yes, in 2023 we also had very anomalously warm ocean temperatures – not as warm as they are now, but at the time, we were amazed (SN: 8/9/23). But we were also getting the start of a very strong El Niño (SN: 15.6.23). To at least put the brakes on somehow [to Atlantic hurricane activity].

This year, El Niño is already gone. [ENSO] it is in the neutral phase now, towards La Niña. We expect to be in full La Niña at the height of hurricane season. And La Niña increases hurricane activity by reducing wind shear across the tropics. [Wind shear can batter at a hurricane’s structure, helping to break it apart.]

SN: And that’s why this year’s hurricane season predictions were so dire?

McNoldy: This is exactly why the seasonal forecasts were the most aggressive forecasts they have ever produced. All you can do [in forecasts] the conditions of the previous years were taken in the simulations. But we’ve never had a year like this. It’s a bit ominous.

SN: This year has kind of a perfect storm of conditions – but what about the forecast for the next few years?

McNoldy: The oceans are warming. It doesn’t mean that every year, we get warmer than the year before, but the trend is definitely there. Maybe in 2025 ocean temperatures won’t be as warm as this year. But at some point, it would be nice to go back to the way things were. This almost seems like a foreign climate at this point.