The storm could be as strong as a Category 2 or 3 hurricane when it approaches Florida on Tuesday into Wednesday, although the intensity forecast is uncertain.
As soon as early Tuesday, tropical storm conditions could begin over the Florida Keys and South Florida.
The storm has the potential to produce “significant impacts from storm surge, hurricane-force winds, and heavy rainfall,” the Hurricane Center wrote Friday. “Residents … should ensure they have their hurricane plan in place and closely monitor forecast updates through the weekend.”
The storm could be called Hermine or Ian, depending on whether this depression or another one, just west of Africa, organizes first.
It appears likely that this system will become the first hurricane to strike the mainland United States this year, and watches are possible by the end of the weekend for parts of Florida and the Florida Keys.
For now, the storm is still about 72 hours away from its first landfall in Cuba. Ahead of the storm’s approach, National Weather Service offices in the central and eastern United States are launching extra weather balloons to draw in added data to improve forecasts.
On Friday morning, the depression was about 500 miles east of Jamaica. Winds were around 35 mph, or below the 39 mph threshold needed for the system to earn a name as a tropical storm.
An Air Force Reserve Hurricane Hunter reconnaissance aircraft was dispatched Friday morning to fly into and investigate the fledgling system.
On visible satellite, it’s evident that all the storminess is displaced to the west of a low-level swirl that has become the system’s de facto center of circulation. This is due to wind shear, or a change of wind speed and/or direction with height. Easterly winds become stronger with altitude, so the system is somewhat tilted.
That shear is stemming from “outflow,” or exhaust, from Hurricane Fiona a few thousand miles to the northeast. Until that shear relaxes on Sunday, the tropical depression will be teetering off-kilter and won’t be able to fully develop. Thereafter, however, conditions will become much more favorable for intensification.
On Sunday, shear buffeting the tropical depression will weaken markedly. At the same time, the system will slip beneath a zone of clockwise-spinning high pressure aloft. That will help to evacuate air away from the system’s center at high attitudes, enhancing upward motion within the developing storm and fostering additional strengthening. That also means more moisture-rich air in contact with the sea surface will be able to enter the storm from below.
The waters of the northwestern Caribbean are very warm, replete with thermal energy to fuel potentially explosive strengthening. That could easily help the system intensify to a Category 2 or stronger hurricane before it strikes Cuba. At present, the National Hurricane Center is predicting landfall early Tuesday west of Havana.
Before reaching Cuba, the storm is forecast to pass just south and then west of Jamaica, where four to eight inches of rain could fall and trigger flash flooding and mudslides.
As the storm crosses Cuba on Tuesday, some weakening is probable before the storm curves toward the northeast over the warm waters of the eastern Gulf of Mexico, where it should regain some strength.
While the gulf is extremely warm, its possible some dry air and wind shear in the storm’s vicinity could limit the storm’s intensification. Still, the Hurricane Center projects that the storm will be a Category 3 hurricane Wednesday morning while centered very near Florida’s west coast.
It is too soon to say exactly where along Florida’s coast the storm might strike. It is still five days away, and track forecasts this far in advance have large errors. There is still an outside chance that the storm track shifts west, more toward the central gulf, or toward the southern tip of Florida or even offshore to the peninsula’s east.
After the storm potentially strikes Florida, it could then move up the Eastern Seaboard or just offshore, affecting coastal areas of the Southeast, Mid-Atlantic and even the Northeast later in the week. But there is much lower confidence in the forecast beyond Wednesday.