(Reuters) -Hurricane Erin has re-intensified into a category 4 storm on Sunday after completing an eyewall replacement cycle, with the U.S. National Hurricane Center warning of life-threatening surf and rip currents along the U.

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.

Hurricane Erin continues to rapidly intensify in the Atlantic Ocean with its outer bands starting to impact the northern Leeward Islands.

SAN JUAN, Puerto Rico (AP) — Erin strengthened into a powerful Category 4 hurricane in the Caribbean on Saturday and continues to intensify, the National Hurricane Center said. The storm is 150 miles northeast of Anguilla with maximum sustained winds of 145 mph. It is moving west-northwest at 20 mph (31 kph).

Charley roared ashore near Cayo Costa, Florida, or west of Fort Myers, packing maximum sustained winds of 150 mph on the afternoon of Aug. 13, 2004. The intensification of Charley prior to landfall was a worst-case scenario since nearly eight hours earlier over the eastern Gulf, it was a Category 2 with 110 mph winds.