Tropical Storm Fiona is forming, soon to hit the Lesser Antilles, Puerto Rico

Tropical storm warnings have been lifted for the northern Leeward Islands — including Saba, St. Eustatius, St. Martin, Antigua and Barbuda, St. Kitts and Nevis, Montserrat and Anguilla — and could be expanded to Puerto Rico and the US Virgin Islands by Thursday afternoon or evening. The current watches will likely be upgraded to warnings because the 50-mph storm is moving west at 14 mph.

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Winds are likely to reach tropical storm strength starting Friday night and will accompany heavy rainfall in the range of 3 to 6 inches. After passing near or over Puerto Rico, Fiona looks forward to bending north, at which point a jigsaw puzzle made up of uncertain atmospheric components will play a west-east tug of war to determine where she will eventually go.

Fiona is the sixth named storm of what has so far been a relatively calm hurricane season in the Atlantic. The Atlantic basin operates about 47.4 percent of the average ACE, or accumulated hurricane energy — a measure of a storm’s overall activity.

According to hurricane researcher Philip Klotsbach, this is the slowest start to a season since 2014, defying experts’ predictions for a particularly active 2022 season. By comparison, the very busy 2021 season had already set off 20 named storms and was on the verge of immersion in the Greek alphabet.

As of 11 a.m. ET Thursday, Fiona’s center was located about 495 miles east of the Leeward Islands and was moving west at a typical pace. This westward movement is expected to continue through Friday, when Fiona will make impacts on the islands and Puerto Rico.

Maximum winds were estimated at 50 mph, and the National Hurricane Center expects a subtle strengthening to a gust of 55 mph. After that, a plateau in intensity is expected as it continues further west. The agency has asked ships within 300 miles of the storm’s location to record and submit weather observations every three hours, which will aid in forecasting and modeling efforts. A US Air Force Hurricane Hunter will be dispatched to investigate the storm later Thursday.

In infrared satellite images, Fiona is full of deep convection, or showers and thunderstorms. This is evidenced by the dark red and white hues, which signify high, cool cloud tops. But the majority of the storm migrates to the east of its low-level circulation—note in white that the low-level cloud field ascends to the center, which is obscured by higher clouds to the east.

This lack of vertical alignment of the system is the result of westerly to northwest winds shearing, or changing wind speed and/or direction with altitude. It knocks the system down, and until it can better stack itself vertically, Fiona will struggle to condense. Strengthening isn’t really expected in the near term, as the mowing doesn’t seem to relax any time soon.

Ultimately, the low-level center may become extended if a thunderstorm and associated updraft pass over said vortex, but it remains to be seen if that will happen before reaching Puerto Rico.

Fiona is expected to bring impacts to the northern Leeward Islands from late Friday, and its core should cross the archipelago early Saturday. A general rainfall of 3 to 6 inches is expected, with higher amounts likely locally. Storm storms with winds approaching 50 to 60 mph are also likely, along with dangerous coastal currents.

From there, the US model (GFS) hints that Fiona can track northern Puerto Rico while still surveying the northeastern edge of US territory.

Conversely, the European model simulates a route south of Puerto Rico and eventually to Hispaniola. This could disrupt the storm’s rotation before it appears over the waters of the southeastern Bahamas. Heavy storm rain over the Dominican Republic and Haiti may cause flooding and landslides, particularly in mountainous areas where there is the potential for double-digit totals.

Hurricane Center forecast for Fiona’s path splits the difference between the US and European models, and calls for a path over Puerto Rico before Fiona sails into the Mona Pass west of the island and east of Hispaniola as it begins a northward bend. The final wild card, and then the different path scenarios, is when that right-north direction occurs, which depends on the strength and location of the high pressure in the Northeast. That high served as a handrail.

Eventually, Fiona will be directed north, where if she evades the Earth and her inner core remains intact, she may begin to condense in the next five to seven days.

Some computer simulations suggest that it will pass close to the east coast, head west from the Bermuda elevation and pull further toward the coast by approaching low pressure in an effort to capture it. Other models allow it to escape into the sea, which could pose an even greater danger to Bermuda. Finally, it’s too soon to tell – but this is something you’ll want to keep a close eye on.