Hurricane Erin was downgraded to a Category 3 hurricane early Sunday as a tropical storm warning was issued for the Turks and Caicos Islands and winds and heavy rains whipped the Virgin Islands and Puerto Rico.

Hurricane Erin forges ahead on a western track at 16 mph, but Miami's NHC expects the hurricane will soon round a corner

The National Hurricane Center is monitoring two disturbances in the Atlantic. A third, Tropical Storm Dexter, the fourth named storm of the season, continues to move out to sea. Why it matters: August is usually when hurricane season ramps up,

Storms that ramp up so quickly complicate forecasting and make it harder for government agencies to plan for emergencies. Hurricane Erick, a Pacific storm that made landfall June 19 in Oaxaca, Mexico, also strengthened rapidly, doubling in intensity in less than a day.

The National Hurricane Center is tracking Tropical Storm Dexter, Invest 96L and system off the southeastern coast of the United States.

National Hurricane Center in Miami, Florida, an area of low pressure was expected to form along a frontal system off of the southeastern coast of the United States. Additional slow development could occur through early next week.