Tropical Storm Lala forms near Hawaii, hurricane watch issued for the Big Island

Tropical Storm Lala formed Thursday in the Pacific Ocean, and it could bring heavy rain and flooding to the Hawaiian Islands this weekend.

A hurricane watch was issued for the Big Island of Hawaii as Lala is forecast to bring rain to the region starting late Friday, the Miami-based National Hurricane Center said.

Lala is about 680 miles east-southeast of Hilo, Hawaii, moving west with maximum sustained winds of 40 mph and could bring high winds and dangerous surf and rip currents.

According to forecasters, Lala is expected to strengthen and could be near hurricane strength as it approaches the Big Island. The center warned that wind speeds on the windward sides of hills and mountains are often up to 30% stronger than near-surface winds.

The forecast track has the storm near or just south of the Big Island on Saturday, and it will pass south of the smaller islands during the rest of the weekend.

Lala could bring rainfall totals of 5 to 10 inches to the Hawaiian Islands, with up to 20 inches possible, forecasters said.

"This rainfall may produce life-threatening flooding and mudslides, especially in areas of steep terrain," the NWS said.

Elsewhere in the Pacific, Tropical Storm Hernan formed Thursday about 1,460 miles west of the southern tip of Baja California. The storm is not expected to threaten land.