Hurricane Iselle picked up strength in the open Pacific on Monday as the powerful storm barrelled toward Hawaii, US forecasters said.
The Miami-based National Hurricane Center upgraded Iselle -- now some 1,245 miles (2,005 kilometers) east of Hilo, Hawaii -- to a Category Four storm on the five-level Saffir-Simpson scale.
Earlier Monday, it had been listed as a Category Three storm.
In its latest advisory, the NHC forecast a "gradual weakening" over the coming days and, on its current trajectory, Iselle could reach Hawaii as a tropical storm by early Friday.
At 1500 GMT, Iselle was packing maximum sustained winds of 140 miles per hour (220 kilometers per hour) and moving west near 10 miles per hour, it said.
No coastal watches or warnings are in effect.
Separately, the NHC warned that Tropical Storm Julio -- swirling in the Pacific about 900 miles southwest of the southern tip of Baja California -- could be near hurricane strength by Wednesday.
At 1500 GMT, Julio was packing maximum sustained winds of near 45 miles per hour and advancing to the west at about 13 miles per hour.