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 threatened the East Coast with dangerous rip currents as the large storm was expected to grow while moving on a projected path up the Atlantic Ocean, the National Hurricane Center in Mi