Tropical storm warnings for the northern Leeward Islands — including Sabah and St. Eustatius, St. Maarten, Antigua, Barbuda, St. Kitts, Nevis, Montserrat and Anguilla — may be extended to Puerto Rico and the U.S. Virgin Islands Thursday afternoon or evening. Existing watches will be upgraded to a warning as the storm gusts to 14 mph to the west at 50 mph.
Tropical storm-force winds will arrive Friday night and bring heavy rain in the 3 to 6 inch range. After passing near or over Puerto Rico, Fiona sees a northward bend, at which point a jigsaw puzzle of uncertain atmospheric materials will play out a west-versus-east tug-of-war that will ultimately determine where it heads.
Fiona is the sixth named storm in what has, until now, been a relatively quiet Atlantic hurricane season. The Atlantic basin averaged 47.4 percent for ACE, or accumulated hurricane energy — a measure of overall storm activity.
According to hurricane researcher Philip Klotzbach, this is the slowest start to a season since 2014, exceeding expert predictions for a particularly active 2022 season. By comparison, 2021’s peak season had already eclipsed 20 named storms and was on the verge of dipping into the Greek alphabet.
As of 11 a.m. Thursday, Fiona’s center was located about 495 miles east of the Leeward Islands and moving west at a typical speed. Westward motion is expected to continue through Friday, when Fiona will have impacts over the Fiona Islands and Puerto Rico.
Maximum sustained winds are estimated at 50 mph, and the National Hurricane Center expects moderate strengthening to a 55 mph storm. Thereafter, a plateau in intensity is expected as it continues westward. The agency asked ships within 300 miles of the storm’s position to record and submit weather observations every three hours to help with forecasting and modeling efforts. An Air Force Hurricane Hunter aircraft will be sent to monitor the storm later Thursday.
In infrared satellite images, Fiona is full of deep convection or shower and thunderstorm activity. Darker reds and whites indicate cooler cloud tops. But the bulk of the storm has migrated east of its low-level circulation – note the low-level cloud field swirling in the center in white, which is obscured by higher clouds to the east.
The system’s lack of vertical alignment is a result of west-to-northwest wind shear, or a change in wind speed and/or direction with height. This knocks the system off-kilter, and until it stacks vertically better, Fiona will struggle to intensify. A consolidation is not expected in the near term as it will not relax anytime soon.
Ultimately, if a thunderstorm and associated development moves past that particular vortex, the low-level center could extend, 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 beginning late Friday, and its center should cross the archipelago early Saturday. Generally 3 to 6 inches of rain is expected, with higher amounts inland. Fast-moving hurricanes with dangerous coastal rip currents with winds of 50 to 60 mph are also possible.
From there, the US (GFS) model indicates that Fiona could track north of Puerto Rico over the northeastern border of the US territory.
Instead, the European model simulates a track south of Puerto Rico and eventually into Hispaniola. This could disrupt the storm’s circulation before it emerges over the waters of the southeastern Bahamas. The storm’s heavy rains over the Dominican Republic and Haiti could lead to flooding and landslides, with the potential for double-digit downpours, especially in mountainous areas.
The hurricane center forecast for Fiona’s track splits the difference between the US and European models, calling for Fiona to lead the Mona Passage west of the island and east of Hispaniola before crossing Puerto Rico as it begins a northward bend. The final wild card, and therefore different track scenarios, will depend on the strength and position of high pressure in the northeast when it turns right to the north. That high acts as a guard.
Eventually, Fiona will move northward and, if it avoids land and its inner core remains intact, will begin intensifying over the next five to seven days.
Some computer model simulations show it moving ominously near the eastern seaboard, moving westward over the Bermuda High, and trying to catch up with the low pressure approaching the coast. Other models allow it to go out to sea, which poses a greater risk to Bermuda. All told, it’s too early to tell – but you should pay close attention to this one.