Tropical Storm Erika is approaching the Leeward Islands from the Atlantic, and forecasters say it may gain strength.

Erika was centered Tuesday evening about 545 miles (875 kilometers) east of Antigua and moving west at 20 mph (31 kph). It had top sustained winds of 40 mph (65 kph).

Tropical storm watches were issued in the Leeward Islands for Montserrat, Antigua and Barbuda, St. Kitts and Nevis, Anguilla, Saba, St. Eustatius, St. Maarten, Guadeloupe, St. Martin, and St. Barthelemy. The watches means tropical storm conditions are possible within 48 hours.

Meanwhile, Tropical Storm Ignacio became the ninth named storm of the eastern Pacific season Tuesday. Ignacio has top sustained winds of 40 mph (65 kph), strengthening quickly as it moves west some 1,530 miles (2,460 kilometers) east-southeast of Hilo, Hawaii.