Fiona grew steadily stronger overnight, and its winds approached hurricane force (75 mph or stronger) this morning as its formative eyewall begins to scrape the southern reaches of Puerto Rico.
The biggest concern for Puerto Rico and the eastern Dominican Republic thereafter is flooding and mudslides from torrential rains forecast in places as high as 25 inches and may rival historic island rainmakers of the past Hurricane Hortense in 1996which devastated parts of the US island territory.
After central pressures hovered in the 1000-1005 mb range for days – the storm was held in check by sustained wind shear – the upper level pattern around Fiona relaxed its grip yesterday, allowing storms to envelope its circuit and pressures to fall into this morning until the late 980s from the latest vortex data message from hurricane hunters. Both microwave satellites and conventional Puerto Rico radar show a formative eyewall that wraps almost entirely around Fiona’s depression center, with its strongest winds about 35 miles northeast and less than 50 miles south of Puerto Rico.
winds sometimes have Gust of 50-60 mph on the south and east sides of the island this morning. Much of the southern half of Puerto Rico is 1,000 feet or higher above sea level, meaning winds at these elevated locations can be 25 to 30 percent higher than the maximum surface winds reported in forecast recommendations.
While the weak power grid in Puerto Rico remains a concern due to strong and gusty winds, the main threat in the coming hours will be potentially catastrophic rains. In Friday’s newsletter, we discussed the destructive water effects of even moderate tropical storms like Erika in 2015, which caused catastrophic flooding in Dominica in the eastern Caribbean. Fiona wrung out nearly 20 inches of rain into the early hours of Saturday over Guadeloupe, Dominica’s northern French neighbor, causing destructive flash floods and mudslides that chewed up streets and homes and killed at least one person. Fiona is expected to bring widespread heavy rains to Puerto Rico through Monday, with up to two feet of rain possible in the eastern and southern parts of the island.
Beyond Puerto Rico and the Dominican Republic, Fiona will bend northwest toward the Turks and Caicos Islands and the southeastern Bahamas late Monday and early Tuesday as a strengthening hurricane.
As we mentioned in newsletters earlier this week, high altitude missions by Hurricane Hunters, which began last night and went into the nightly computer model runs, have helped stabilize the models, giving us a clearer picture of next week’s forecast. Fiona is not expected to pose a threat to South Florida or the US mainland, but the Bahamas will need to monitor her progress through the middle and end of the week.
Aside from Fiona, the tropics are looking mercifully quiet this week, with the only area of potential development from a north-moving system over the central open Atlantic.
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https://www.local10.com/weather/2022/09/18/fiona-almost-a-hurricane-bearing-down-on-puerto-rico/ Fiona almost like a hurricane hitting Puerto Rico