Hurricane Guillermo last night intensified to a Category 3 storm, but forecasters said it is expected to gradually weaken beginning today as it continues to head toward the Islands.

At 11 p.m. yesterday, Guillermo was about 1,600 miles east of Hilo and moving west-northwest at 16 mph. The storm had maximum sustained winds of 115 mph, which extended about 35 miles from Guillermo's center.

The National Hurricane Center upgraded it at 7:30 p.m. from a Category 2 hurricane.

Guillermo is forecast to cross 140 degrees west longitude and enter the Central Pacific, commonly called "Hawaiian waters," tomorrow afternoon as a tropical storm and continue to weaken as it moves over cooler waters.

Jonathan Hoag, National Weather Service forecaster, said it's still too early to predict if the storm will have any effect on the state's weather. The National Hurricane Center's five-day track has the storm to the northeast of the Big Island Tuesday afternoon as a tropical depression.

"Weakening tropical systems still have potential for wind damage and localized heavy rains and flooding," Hoag said. "But at present it's too distant and too far away in time to be sure of what the specific effects would be. So all we do is generalize."

Remnants of the former Hurricane Felicia passed by the Islands this week and brought heavy rain to parts of Kaua'i and O'ahu. Hoag said similar rain would be welcome in other parts of the state.

"We might hope for rainfall from a weakening tropical system over the Big Island and Maui because they're so short," Hoag said of drought conditions in parts of those Islands.