Tropical Storm Gonzalo formed Wednesday morning over the open Atlantic and is headed west toward a potential rendezvous with the Caribbean by early next week. Gonzalo is the earliest “G” storm on record in the tropical Atlantic. According to the National Hurricane Center (NHC), Gonzalo is forecast to become a hurricane by Thursday, but it should subsequently weaken back to tropical storm status soon after that.
At the same time, a second system lurking west of Florida is also raising a few eyebrows as it drifts west into the Gulf of Mexico. The National Hurricane Center (NHC) is giving that system a 50 percent chance of developing into a tropical depression over the next few days.
Gonzalo’s development is the latest in a string of impressive milestones claimed by the record-busy start to the 2020 hurricane season. This year has already featured the earliest C, E and F storms on record — Cristobal, Edouard and Fay — and Gonzalo just snagged its own record. The previous top spot was held by Tropical Storm Gert, which formed in the Bay of Campeche on July 24, 2005, before striking Mexico.
The average date of an Atlantic hurricane season’s seventh named storm is Sept. 16.
Behind Gonzalo, models are hinting that a third system, a fledgling African easterly wave, could develop after it emerges off the coast of western Africa.
Gonzalo forms Wednesday morning
At 11 a.m. Eastern time on Wednesday, Tropical Storm Gonzalo was centered about 1,200 miles east-southeast of the Windward Islands, moving west at about 14 mph. Gonzalo’s estimated maximum sustained winds ticked upward to 50 mph.
In the coming days, Gonzalo is likely to intensify into a hurricane by Thursday and maintain that intensity through Friday before weakening into a tropical storm through early next week. Water temperatures are plenty warm to support strengthening, but dry air, coupled with wind shear — or a change of wind speed or direction with height — could act against Gonzalo’s maturation by interfering with the organization of its thunderstorms.
Eventually, Gonzalo may encounter some more supportive surroundings over the weekend, allowing for some strengthening.
Currently, the NHC projects Gonzalo to boast maximum sustained winds of roughly 65 to 70 mph as it slips through the southern Windward Islands on Saturday afternoon into Sunday. However, storm intensity forecasts have a high amount of uncertainty so far in advance. While Gonzalo’s strongest winds may be found right around its center, heavy rains from the storm could affect a broader area.
For the time being, predicting Gonzalo’s future intensity and its track will be made all the more difficult by the cyclone’s diminutive size. Smaller cyclones are more fickle and can be sensitive to subtle environmental changes. They can pulse up and downward in intensity on short order, yielding an additional challenge for forecasters.
A potential ‘homegrown’ tropical system
Meanwhile, a second system is brewing closer to home. A weather system designated Invest 91L consists of a broad cluster of thunderstorm activity anchored about 300 miles west of the Florida Keys, and it has a 50 percent chance of developing into a tropical depression, according to the NHC.
Tropical depressions have winds of 34 to 39 mph, and such systems are the precursors to tropical storms.
A slow and steady organization of 91L is expected in the coming days as it fends off dry mid-level air to its west. That moisture-starved air mass was apparent on satellite imagery Wednesday morning.
On Tuesday, heavy downpours arcing into the broad system from the east brought 3.11 inches of rain to Miami-Dade County, Fla., while parts of the Keys saw several inches as well.
Looking ahead, 91L is forecast to continue drifting to the northwest, taking advantage of Gulf of Mexico water temperatures that are running close to a degree above average for this time of year.
By Friday, the system’s center — regardless of how organized it is at that point — may approach the Texas or Louisiana coastline.
Neglecting wind speeds, which are predicated more on the system’s overall intensity at that point, heavy rain appears to be a certainty for areas impacted by the system. An early look at data suggests the heaviest rain may fall along the coast between Matagorda Bay in Texas and New Orleans, although that area will be refined as we get closer to the weekend.
Several inches of rain are possible, with the threat of inland flooding. It’s not out of the question that one or two communities see upward of a half foot of rain.
On the outside chance that 91L intensifies and is eventually named as a tropical storm, “Hanna” will be up next after Gonzalo.
Forecasters have been anticipating an unusually active 2020 hurricane season, due to a number of factors. These include atmospheric circulation patterns, such as a developing La Ninã in the tropical Pacific Ocean, that would make the Atlantic more ideal for storm formation.
Anomalously warm water temperatures this season also shift the odds toward potentially stronger and more quickly intensifying storms this year, both trends linked in part to human-caused climate change.
Atlantic hurricane season typically peaks around Sept. 15.