Photo Gallery: Hurrricane Isaac 31/70

A message warns drivers of severe weather on Sunday, Aug. 26, 2012, in Miami. Isaac gained fresh muscle Sunday as it bore down on the Florida Keys, with forecasters warning it could grow into a dangerous Category 2 hurricane as it nears the northern Gulf Coast. (AP Photo/The Miami Herald, Hector Gabino) ORG XMIT: FLMIH102