Tropical Storm Darby bore down on Hawaii on Saturday, prompting its governor to declare an emergency over a storm expected to make landfall with strong winds and heavy rain later in the day. Forecasters said Darby would reach the U.S. state’s Big Island on Saturday when maximum sustained winds could near 50 mph (80 kph) and as much as 15 inches (40 cm) of rain could fall, the National Weather Service said in an advisory. The torrential rainfall could cause life-threatening flash floods as well as landslides, it said.