By Karin Stanton
KAILUA-KONA, Hawaii (Reuters) - Tropical storm Kilo formed from a low-pressure system drifting across the central Pacific on Friday on a trajectory that could threaten the Hawaiian islands as it strengthens into a hurricane early next week, the National Weather Service reported.
Kilo, with sustained winds of up to 40 miles per hour (64 mph), was centered roughly 500 miles (800 km) south-southeast off Hawaii's Big Island at 5 a.m. and was forecast to remain on a northwesterly path before possibly taking a sharper turn north on Sunday morning.
Forecasts also call for the storm to grow by the next day into a Category 1 hurricane, with maximum sustained winds of 74 mph (120 kph), said Chevy Chevalier of the National Weather Service's Central Pacific Hurricane Center in Honolulu.
At that point, Kilo would be churning hundreds of miles to the southwest of the island of Kauai, and could strengthen further into a low-end Category 2 hurricane by Wednesday with sustained winds of about 100 mph (160 kph), Chevalier said.
If the storm then drifts easterly at midweek, as some forecasts suggest, Kilo could begin to pose a threat to Kauai and Niihau, a smaller, less populated island at the westernmost end of Hawaii's inhabited island chain.
Kilo, whose storm-force winds extended out more than 100 miles (160 km) from its center on Friday, ranks as the fourth named storm to form in the central Pacific basin this season, Chevalier said.
The formation of Kilo came as Hurricane Danny, the first of the 2015 Atlantic season, strengthened into a potentially destructive Category 3 storm on Friday, with winds measured at up to 115 mph (185 kph), government forecasters said.
Danny was expected to weaken back into a tropical storm as it reaches the outer Caribbean islands early next week.
The most recent Pacific cyclone to make landfall in Hawaii was Iselle, which struck the Big Island as a tropical storm last August. But that storm caused far less destruction than Hurricane Iniki, the most powerful on record to strike Hawaii, which hit Kauai in September 1992 as a Category 4 storm.
(Additional reporting and writing by Steve Gorman from Los Angeles; Editing by Sandra Maler)