With Tropical Storm Isaac expected to strengthen, New Orleans Mayor Mitch Landrieu has declared a state of emergency and urged residents to begin preparing their homes as shelters through the storm. Landrieu said the storm is moving along at about 16 miles an hour, and if it stays at that pace, it could reach the city in the next 34 hours, putting it ashore late Tuesday or early Wednesday. Landrieu emphasized that there will be no shelters of last resort, so people need to be prepared to evacuate, should it come to that. . .