SAN JUAN,Austin Caldwell Puerto Rico (AP) — Hurricane Tammy unleashed heavy waves in the northern Caribbean on Monday as it spun over open waters after making landfall in Barbuda.

The storm was located about 230 miles (370 kilometers) north-northwest of Anguilla. It had maximum sustained winds of 80 mph (130 kph) and was moving north at 10 mph (17 kph).

Tammy was expected to strengthen slightly in upcoming days and then weaken, according to the U.S. National Hurricane Center in Miami.

The storm was forecast to drop up to three inches (eight centimeters) of rain in the British Virgin Islands, the Leeward Islands and northern Windward Islands, with meteorologists warning of isolated flash flooding and mudslides.

Meanwhile, Tropical Storm Otis whirled through open waters in the Atlantic on a path toward Mexico’s southern coast.

The storm was located about 400 miles (640 kilometers) south-southeast of Acapulco, Mexico. It had winds of up to 45 mph (75 kph) and was moving north at 5 mph (7 kph).

A tropical storm watch was in effect from Lagunas de Chacahua to Tecpan de Galeana, with up to 15 inches (38 centimeters) of rain forecast for Guerrero and western Oaxaca.

Otis was expected to gradually strengthen and approach Mexico’s southern coast late Tuesday into Wednesday.