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.

BEAUMONT, Texas — Tropical Storm Erin is moving quickly westward across the Atlantic Ocean and could strengthen into a hurricane by late Thursday, prompting the National Hurricane Center to advise residents of the northern Leeward Islands, Virgin Islands and Puerto Rico to monitor the storm's progress.