A potential threat posed by Tropical Storm Fiona prompted the issuance of Tropical Storm Warnings for some of the Leeward Islands. At 11:00 a.m. EDT on Thursday the center of Tropical Storm Fiona was located at latitude 16.6°N and longitude 54.3°W which put it about 495 miles (800 km) east of the Leeward Islands. Fiona was moving toward the west at 14 m.p.h. (22 km/h). The maximum sustained wind speed was 50 m.p.h. (80 km/h) and there were wind gusts to 65 m.p.h. (105 km/h). The minimum surface pressure was 1002 mb.

Tropical Storm Warnings were in effect for Saba, St. Eustatius, St. Maarten, Antigua, Barbuda, St. Kitts, Nevis, Montserrat and Anguilla. Tropical Storm Watches were in effect for Guadeloupe, St. Martin and St. Barthelemy.

Tropical Storm Fiona was being affected by strong vertical wind shear on Thursday morning. The center of Fiona was surrounded by a swirl of showers and lower clouds. Thunderstorms were occurring in bands in the eastern edge of Fiona’s circulation. Tropical Storm Fiona was under the northern part of an upper level ridge over the tropical Atlantic Ocean. The upper level ridge was producing westerly winds that were blowing across the top of Fiona’s circulation. Those winds were causing strong vertical wind shear and the wind shear was blowing the tops off of many of the thunderstorms that start to develop. In spite of the vertical wind shear, the low level circulation around Tropical Storm Fiona was still well organized. Winds to tropical storm force extended out 140 miles (220 km) from the center of Fiona’s circulation.

Tropical Storm Fiona will move through an environment marginally favorable for intensification during the next 36 hours. Fiona will move over water where the Sea Surface Temperatures are near 28˚C. However, the upper level ridge over the tropical Atlantic Ocean will continue to cause vertical wind shear. The wind shear will inhibit intensification. Tropical Storm Fiona could weaken if the upper level winds get stronger. The upper level winds could be weaker when Fiona moves over the northeastern Caribbean Sea during the weekend.

Tropical Storm Fiona will move around the southern side of the subtropical high pressure system over the Atlantic Ocean. The high pressure system will steer Fiona toward the west during the next 36 hours. On its anticipated track Tropical Storm Fiona could approach the Leeward Islands on Friday afternoon. Fiona could bring gusty winds and locally heavy rain to the northern Leeward Islands. Tropical Storm Fiona could be southeast of Puerto Rico by Saturday evening.