The storm is likely to be as strong as a Category 2 or 3 hurricane as it approaches Florida Tuesday through Wednesday, though intensity forecasts are uncertain.
Tropical storm conditions could start over the Florida Keys and South Florida as soon as early Tuesday.
The storm has the potential to produce “significant effects of storm surge, hurricane-force winds and heavy rainfall,” the Hurricane Center wrote on Friday. “Residents…should make sure they have hurricane plans and keep an eye on forecast updates over the weekend.”
The storm could be called Hermine or Ian, depending on whether this depression or another in West Africa organized first.
The system appears likely to be the first hurricane to hit the continental U.S. this year and will be observable over parts of Florida and the Florida Keys by the end of the weekend.
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The storm is currently about 72 hours away from making landfall in Cuba for the first time. Ahead of the storm, National Weather Service offices in the central and eastern U.S. are launching additional weather balloons to get more data to improve forecasts.
The depression was about 500 miles east of Jamaica on Friday morning. Winds were around 35 mph, or below the 39 mph threshold needed for the system to receive a tropical storm designation.
On Friday morning, an Air Force Reserve Hurricane Hunter reconnaissance plane was dispatched to fly in and investigate the fledgling system.
On the visible moon, it’s clear that all storms have shifted west of a low-level vortex that has become the system’s de facto center of circulation. This is due to wind shear, or changes in wind speed and/or direction with height. Easterly winds get stronger with elevation, so the system is a bit tilted.
This shear stems from the “outflow,” or exhaust, of Hurricane Fiona several thousand miles to the northeast. The tropical depression will be too shaky to fully develop until Sunday’s shear relaxes. After that, however, conditions will become more favorable for intensification.
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On Sunday, the shear force of the tropical depression will weaken significantly. At the same time, the system will slide under a high pressure area that rotates clockwise. This will help evacuate air from the center of the system at high attitude, enhance the upward movement of the developing storm and facilitate additional strengthening. It also means that more moisture-rich air in contact with the sea surface will be able to enter the storm from below.
The waters in the northwestern Caribbean Sea are very warm and full of thermal energy that could fuel a potentially explosive intensification. This could easily help the system intensify to a Category 2 or stronger hurricane before hitting Cuba. Currently, the National Hurricane Center is forecasting landfall west of Havana early Tuesday.
Before reaching Cuba, the storm is expected to sweep south and west of Jamaica, where it could drop 4 to 8 inches of rain and cause flash floods and mudslides.
If the storm passes through Cuba on Tuesday, it could weaken somewhat before the storm bends northeast into the warm waters of the eastern Gulf of Mexico, where it should regain some intensity.
While the Gulf is very warm, some dry air and wind shear near the storm may limit the storm’s intensification. Still, the hurricane center projected Wednesday morning the storm would become a Category 3 hurricane with its center very close to Florida’s west coast.
It’s too early to say exactly where the storm could hit the Florida coast. There are still five days from now, and there is a big error in the tracking forecast so long in advance. The storm’s path is still likely to move westward, more toward the Central Gulf, or toward the southern tip of Florida, or even offshore to the east of the peninsula.
After the storm could hit Florida, it could move eastward or offshore, affecting coastal areas in the Southeast, mid-Atlantic and even the Northeast later this week. But confidence in forecasts beyond Wednesday is much lower.