Peak Hurricane Season

Peak hurricane season is here, and though forecasters see a lull for the next two weeks, they also said things could get “interesting” by mid-September.

Introduction to Hurricane Season

There are several key forces at play, from Saharan dust dissipating to extra hot sea-surface temperatures in the Caribbean. A potential La Niña would make storms even more likely.

Factors Influencing Hurricane Formation

“What usually holds tropical storms back earlier in the season is that the water isn’t really warm enough and there’s too much dry air,” said Phil Klotzbach, hurricane specialist with Colorado State University.
By August, things change. The eastern Atlantic starts getting hot enough to support hurricanes, and Saharan dust plumes, which inhibit storms with their dry air, dissipate.
There’s also a wind shear window. “Typically your shear is still fairly low in August,” said Klotzbach. “Later in the season, the wind shear in the eastern and central Atlantic gets too strong.”

Caribbean Heat

Caribbean waters are particularly hot this year, said Klotzbach, which will make storms more likely.
As the season progresses, it’s normal for the Caribbean to become the source of more storms. “Caribbean storms were normally an October phenomenon,” said Fox Weather hurricane specialist Bryan Norcross, “but we’re seeing Caribbean storms in September lately.”
A factor in the Caribbean’s unusually hot water in August was Hurricane Erin. As the massive storm, which reached Category 5, traveled north, away from the Caribbean, its rotation created west winds over the region, which countered easterly trade winds. The net effect was less wind in the Caribbean, which gives the sun a chance to warm the placid water up.

This map, based on data from 1944 to 2020, shows hurricane and tropical storm activity peaking in late August and September. (Courtesy National Hurricane Center)
Klotzbach said the most likely source of storms would be an area called the Caribbean gyre, or Central American gyre, a large slowly circulating low-pressure system that spins over Central America, the western Caribbean and the Yucatan Peninsula. 2024’s Hurricane Helene, which plowed into the Florida’s Big Bend region on Sept. 26, spun up out of the Caribbean gyre.

La Niña, Maybe

The El Niño-Southern Oscillation (ENSO) climate pattern, which produces both El Niños and La Niñas, is currently in a “neutral” state, but it is trending toward a La Niña. Norcross said that the cooler Pacific of La Niña leads to weaker upper level wind shear in the Atlantic Basin, and is thus conducive to hurricanes. Wind shear can topple storms.
Klotzbach said that even though there’s no official La Niña designation yet from the National Oceanic and Atmospheric Administration, there will likely still be a La Niña-ish impact, which would lower wind shear in the Caribbean.
“Lately we’ve had a trend to La Niña developing late in season, therefore making the overall atmospheric pattern more conducive to storms later in the hurricane season,” said Norcross.
It’s not a slam dunk that it will be declared a La Niña by NOAA, but the cool water conditions (cool neutral) does not bode well for the end of the hurricane season in the Caribbean.
Another partner that Norcross sees relates to the Pacific Ocean. “The Eastern Pacific is ticking up right now. There are suddenly three systems. Normally, that Pacific uptick precedes the uptick in the Atlantic by, on average, a week or two. So the signals that we have are that the Atlantic will get busier again in approximately two weeks, so the middle of September.”

Conclusion

With the current temporary lull in tropical activity, the National Weather Service’s Miami office has noticed some social media feeds claiming the season is over, and has encouraged the public to use reliable, science-based sources to stay informed.
Weather models, in fact, indicate a mid-September ramp-up. Klotzbach sees a calm two weeks ahead, but a change after that. “I’d be surprised if the season isn’t looking pretty interesting by around Sept. 10.”

FAQs

Q: What is the current state of the hurricane season?
A: The hurricane season is currently in a temporary lull, but forecasters predict that things could get “interesting” by mid-September.
Q: What factors are contributing to the potential increase in hurricane activity?
A: Several factors, including the dissipation of Saharan dust, hot sea-surface temperatures in the Caribbean, and a potential La Niña, are contributing to the potential increase in hurricane activity.
Q: What is the Caribbean gyre, and how does it relate to hurricane formation?
A: The Caribbean gyre is a large, slowly circulating low-pressure system that spins over Central America, the western Caribbean, and the Yucatan Peninsula. It is a potential source of storms, and 2024’s Hurricane Helene formed out of this gyre.
Q: What is the current state of the El Niño-Southern Oscillation (ENSO) climate pattern?
A: The ENSO climate pattern is currently in a “neutral” state, but it is trending toward a La Niña.
Q: How can the public stay informed about the hurricane season?
A: The public can stay informed about the hurricane season by using reliable, science-based sources, such as the National Weather Service.