Tropical Storm Flossie has formed in the Pacific Ocean about halfway between Hawai'i and Mexico, but its potential effects on the Islands won't be known until tomorrow, the National Weather Service said yesterday.

The storm was about 1,600 miles from Honolulu at 10:45 p.m. Hawai'i time yesterday, according to the National Hurricane Center in Miami, and on a track that would have it passing south of the Big Island late Tuesday.

Flossie was moving west toward Hawai'i at about 14 mph and had maximum sustained winds of 63 mph, the center said.

"The official forecast calls for a gradual strengthening," the center said. The storm had the potential to reach hurricane strength late yesterday and weaken today, forecasters said.

A five-day forecast for Flossie won't be made until tomorrow, when the storm is expected to cross 140 degrees west longitude, said Wes Browning, director of operations at the National Weather Service in Honolulu and deputy director of the Central Pacific Hurricane Center.

"Right now the cone of uncertainty, the potential extended track storm, doesn't even reach the state," Browning said. "It's too early to tell about the potential impacts on the state of Hawai'i. We'll get a much clearer idea as we head into the weekend."

The systems become named storms when sustained winds reach 39 mph.

The National Oceanic and Atmospheric Administration predicted there will be two to three tropical storms in Hawai'i's 2007 hurricane season, which runs from June 1 to Nov. 30.