An eyewall replacement cycle is underway within Hurricane Erin as the monster storm continues to barrel across the Atlantic while bringing gusty winds and rain to Puerto Rico and the Virgin Islands after rapidly intensifying into a catastrophic Category 5 hurricane over the weekend.

Hurricane Erin restrengthened into a Category 4 storm late Sunday, with forecasters warning it is expected to intensify and grow in size in the coming days as it lashes Caribbean islands with heavy rains that could cause flash floods and landslides.

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.

As of 5:00 p.m. AST on Sunday, Erin’s center was positioned approximately 275 miles northwest of San Juan, Puerto Rico, tracking west-northwest at 13 mph. Although no longer directly affecting the area, the storm’s outer bands are still delivering heavy rainfall, dangerous marine conditions, and life-threatening surf along coastal areas.

While the compact hurricane's center wasn't expected to strike land, it threatened to dump flooding rains on the northeast Caribbean as it continued to grow larger.

Hurricane Erin has strengthened into a Category 2 storm as it approaches Puerto Rico and the Virgin Islands, bringing heavy rains that could cause flooding and landslides.

It quickly powered up from a tropical storm to a Category 5 in a single day, the National Hurricane Center said.

Tropical Storm Erin on Tuesday continued to push west through the Atlantic as the National Hurricane Center forecasted it to become a major hurricane with Puerto Rico and other Caribbean islands in its potential path.