Tropical Storm Erika formed late Monday night in the central Atlantic and is about 840 miles east of the Leeward Islands.
Tropical storm watches were posted Tuesday morning for parts of the Leeward Islands, and additional watches and or warnings may be required soon.
Erika is expected to remain a tropical storm and gather strength as it moves quickly to the west.
The northern Leeward Islands may feel tropical storm-force winds by late Wednesday night into early Thursday.
Erika may then bring more rain to drought-suffering Puerto Rico and the Virgin Islands.
Erika's future track and intensity beyond Puerto Rico and the Virgin Islands is highly uncertain.
Tropical Storm Erika formed 955 miles east of the Lesser Antilles and is swirling westward at about 20 mph.
For the next couple of days, Erika will be moving through an environment characterized by a moist air mass, low vertical wind shear and warm water. This should allow some strengthening.
Just like we saw with Danny, Erika will eventually have to battle wind shear and some dry air as it nears the Caribbean. This complicates both the intensity and track forecasts.
Due to this fast movement, Erika is already expected to arrive in the northern Leeward islands Wednesday night or early Thursday with tropical storm-force winds and heavy rain, prompting tropical storm watches to be issued early Tuesday morning for Montserrat, Antigua, Barbuda, St. Kitts and Nevis, Aguilla, Saba, St. Eustatius and St. Maarten.
This is the second time in less than three days watches have been hoisted in the Leeward Islands, done so this past weekend ahead of Tropical Storm Danny, whose remnants are sliding through the Caribbean ahead of Erika.
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NASA satellite hurricane photos from space
Tropical Storm Erika has formed in the Atlantic
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Archive: South Pacific Storm (NASA, Skylab, 12/02/73)
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