A new tropical wave about 350 miles southwest of the Cabo Verde Islands has piqued the interest of the National Hurricane Center, which is giving it a 50 percent chance of development over the next five days.
The system, dubbed 99-L, is a disorganized grouping of showers for now, but warm sea surface temperatures and light wind shear are giving it a chance for gradual development.
A tropical depression could form early next week while the system moves west at about 15 mph, forecasters said this morning in their 2 p.m. advisory.
If the storm gains named status, it would be Gaston.
Brian McNoldy, a senior research associate at the University of Miami Rosenstiel School of Marine and Atmospheric Science, is calling 99-L a “potent easterly wave.”
“Tropical Storm Fiona is on the decline, but may pave the way for a new storm – that may earn the name Gaston – which could become more menacing,” McNoldy wrote in a blog for The Washington Post’s Capital Weather Gang. “Although not even a tropical depression yet, the disturbance near the Cape Verde islands is heavily favored by models to develop and strengthen.”
It doesn’t take much to be more menacing than Fiona, which this morning mustered only 45 mph winds and was expected to weaken over the weekend with no threat to land.
And while McNoldy said it’s hard for forecast models to make intensity predictions this far out, ‘Most models, though not all, forecast Gaston to form and become formidable,” he wrote.
Bob Henson, a meteorologist and blogger with Weather Underground, agreed the newest disturbance is one to watch because it is traveling at a lower latitude with a path aiming at the Lesser Antilles.
“It’s certainly a little more concerning,” Henson said. “It doesn’t have a strong circulation yet, but it’s as big as Fiona, if not larger. It looks like it could be a fairly well sized tropical system if it does develop.”
AccuWeather said in a blog this morning steering winds are taking 99-L much farther to the west than other African easterly waves we’ve seen this year and at the “very least”, showers and thunderstorms will whack the Lesser Antilles next week.
“Dry air and disruptive winds have been a deterrent in this area during much of the summer, but that is beginning to change,” AccuWeather Senior Meteorologist Alex Sosnowski wrote. “Waves of moisture from Africa to the Lesser Antilles have become more extensive this week. The trend is likely to continue in the coming weeks.”
Mark Sudduth, a geographer and founder of Hurricanetrack.com, weighed in on his blog this afternoon. He cautioned looking to far ahead, noting that charts showing too much intensity “only lead to more anxiety when it is probably unwarranted.”
But, he said it’s likely 99-L will be a tropical storm or hurricane sometime next week.
“The first area of concern is for the eastern Caribbean Sea,” Sudduth wrote. “Beyond that, it’s wait and see just like it has been since I began this site back in 1999.”
Tropical Storm Fiona, meanwhile, is on a steady trek west-northwest with maximum sustained winds of 45 mph and a minimum central pressure of 1006 mb.
Fiona is expected to weaken over the weekend as it runs into more wind shear and drier mid-level air, the National Hurricane Center said.
“While the environmental conditions might get less hostile at the end of the period, it is uncertain how much will be left of Fiona at that time to take advantage of that change, with some suggestion in the global models that Fiona could decay to a remnant low by then,” forecasters wrote in a 5 a.m. advisory.