Oahu has joined Maui County and the Big Island under a tropical storm warning as Olivia continues to march west packing maximum sustained winds of 70 mph.

Kauai County is now under a tropical storm watch.

As of 5 p.m. Monday, the National Weather Service advised that Olivia was about 530 miles east of Honolulu and about 380 miles east-northeast of Hilo.

A tropical storm warning means storm conditions are expected within 36 hours, while a watch means they are expected within 48 hours..

“On this forecast track, tropical storm conditions are expected over parts of Hawaii starting late Tuesday,” the NWS said. “Little change in strength is forecast today, with slight weakening starting tonight and continuing through Tuesday. However, Olivia is forecast to be a strong tropical storm when it reaches the Hawaiian Islands.”

NOAA

The advisory continued:

• Rainfall: Olivia is expected to produce total rainfall accumulations of 10 to 15 inches. Isolated maximum amounts of 20 inches are possible, especially over windward sections of Maui County and the Big Island. This rainfall may produce life-threatening flash flooding.

• Surf: Large swells generated by Olivia will spread from east to west across the Hawaiian Islands early this week. This will cause surf to build along exposed east facing shorelines as Olivia approaches. This surf may become damaging across parts of the state.

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