Hurricane Erin could 'at least double or triple in size' next week and the track has shifted south, but remains likely to turn away from the East Coast.

Storms that ramp up so quickly complicate forecasting for meteorologists 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 rapidly intensified to a Category 5 storm on Saturday and is headed north through the Atlantic, where it's expected to miss the U.S., but bring dangerous conditions to coastal areas.

Tropical Storm Erin is expected to become a hurricane later today, Aug. 15, and a Category 4 hurricane with maximum sustained winds of 130 mph over the weekend. A major hurricane is a Category 3 or stronger, with maximum sustained winds of at least 111 mph.