While Erin is expected to take a northward turn in the Atlantic, a new system off the coast of Africa has the National Hurricane Center's attention.

The storm will remain a major hurricane through the middle of the week, according to the National Hurricane Center.

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.

Erin is a Category 3 hurricane, the National Hurricane Center said in its 5 p.m. ET update Sunday, with sustained winds of 125 mph and tropical storm-force winds reaching out 205 miles. The storm is expected to continue to fluctuate in intensity and could double or even triple in size as it moves north and west,

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.

Erin, the first hurricane of the season, is now forecast to become a Category 4 by Sunday. Here's where it could head in the week ahead.

Hurricane Erin pelted parts of the Caribbean and was forecast to create dangerous surf and rip currents along the U.S. East Coast this week