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.

Parts of North Carolina's Outer Banks have been placed under a tropical storm and storm surge watch as the still-growing, powerful, major Hurricane Erin begins a northward turn Tuesday that could send hazardous surf,