Wednesday marked the peak of hurricane season. Not that Floridians are complaining, but the tropics have been exceptionally quiet. The last storm the Fox 4 Weather Team tracked was Tropical Storm Fernand, which dissipated over the open Atlantic on August 28th.
According to Dr. Phil Klotzbach, Senior Research Scientist at Colorado State University, there’s only been one year since 1950 with no storms between August 29th and September 15th. (That was in 1992 after Hurricane Andrew devastated South Florida.)
I asked Dr. Klotzbach the reason behind the lull in storms, during what is traditionally the most-active time of year.
He explained that the atmosphere has been exceptionally dry and stable across the tropical Atlantic. But the biggest factor has been strong vertical wind shear, or how winds change direction and speed with height. That strong shear helps to rip apart storms.
“Right now we do have fairly enhanced vertical wind shear that’s stronger than normal. We have what we call a tropical upper tropospheric trough, so an area of low pressure high up in the atmosphere and that tends to lead to strong shear,” he explained.
That’s why last week’s disturbance (91L) over the Atlantic fizzled; it was sheared apart by strong winds aloft. That wind shear is expected to weaken in the next couple weeks, allowing for more development in the eastern Atlantic, as waves roll off the coast of Africa.
It’s also during the second half of the season that we tend to see more formation in the Gulf and Caribbean.
“Over 50% of storms that form in the Caribbean during the hurricane season do so in October and November, so the Caribbean really tends to be busy late. That’s because the waters are very warm, and the shear tends to stay low. It becomes a breeding ground for late season storms,” Dr. Klotzbach explained.
Ian, Helene and Milton, our past three major hurricanes to impact SWFL, all developed in late September or early October in the Caribbean Sea or Gulf, not the Atlantic.
Dr. Klotzbach cautions, “It remains to be seen.... Let’s hope it stays quiet but we do on average have half the season left to go.”
