A typhoon that had left the Philippines after killing nearly 600 people and leaving hundreds missing in the south has made a U-turn and is now threatening the country’s northwest, officials said Saturday. The weather bureau raised storm warnings over parts of the main northern island of Luzon after Typhoon Bopha veered northeast. There was a strong possibility the disastrous storm would make a second landfall Sunday, but it might also make a loop and remain in the South China Sea, forecasters said. In either case, it was moving close to shore and disaster officials warned of heavy rains and winds and possible landslides in the mountainous region.