MIAMI, Florida (CNN) -- Tropical Storm Erika was poorly organized and barely clinging to tropical-storm status late Wednesday, and it was expected to weaken further on Thursday, the National Hurricane Center said.
Late Wednesday, Erika was becoming more unorganized and barely clinging to tropical-storm status.
Erika's winds were near 40 mph (65 kph) with higher gusts, forecasters said. If its winds drop below 39 mph, Erika will become a tropical depression. "Little change in strength is forecast during the next 12 hours, but a gradual weakening should begin thereafter," the hurricane center said.
A tropical storm warning remained in effect for the islands of Dominica, Guadeloupe, St. Martin, St. Barthelemy, Antigua, Barbuda, Montserrat, St. Kitts, Nevis, Anguilla, St. Maarten, Saba and St. Eustatius. A tropical storm warning means that tropical storm conditions, including winds of at least 39 mph, are possible within 24 hours.
A tropical storm watch, meaning tropical storm conditions are possible within 36 hours, was in effect for Puerto Rico and the U.S. and British Virgin Islands. The Dominican Republic and Haiti, meanwhile, were advised to monitor the storm's progress.
As of 11 p.m. ET Wednesday, Erika's center was about 70 miles (110 km) west-southwest of Guadeloupe, and about 290 miles (470 km) east-southeast of San Juan, Puerto Rico, the hurricane center said.
It was moving west at near 9 mph (15 kph) and was expected to gradually turn west-northwest on Thursday.
"On the forecast track, the weather associated with Erika will continue to move through the Leeward Islands early Thursday and approach Puerto Rico late tomorrow," the hurricane center said.
The storm, which formed Tuesday evening, briefly strengthened overnight before losing some of its steam.
Rainfall amounts are expected to total 2 to 4 inches over the Lesser Antilles over the next few days, with isolated amounts up to 6 inches. Between 3 to 5 inches of rain are forecast for Puerto Rico, with isolated amounts of up to 8 inches.
Tropical storm-force winds extended outward about 175 miles (280 km) to the east of Erika's center, the hurricane center said. See Erika's projected path »
Tracking maps show Erika brushing the northern part of Hispaniola, the island shared by Haiti and the Dominican Republic, before nearing the Bahamas on Sunday.