Hurricane Iselle intensified into a category 4 hurricane with sustained winds of 135 mph as a new tropical storm formed behind it in the Eastern Pacific.
Iselle is moving west at 8 mph on a path toward Hawaii and was 1,150 miles east of Hilo at 5 p.m.
A flood potential outlook issued by the National Weather Service Monday afternoon says heavy rain and flash flooding is possible Thursday and Friday.
“The latest forecast from the National Hurricane Center in Miami shows Iselle reaching the vicinity of the Big Island as a tropical storm by Thursday night/early Friday morning,” forecasters said.
Forecasters are estimating winds of 45 to 55 mph, with gusts of up to 80 mph Thursday night on windward slopes of Haleakala on Maui.
The current long-range forecast for Honolulu and southern shores of Oahu calls for possible tropical storm conditions starting Thursday night and continuing into Friday, with 45 to 50 mph winds with gusts to 75 mph after midnight Thursday. Forecasters estimate a 100 percent chance of rain.
However, forecasters caution that small changes in the storm’s path will change the forecast, which will also change as the storm track is updated.
“Due to uncertainty in the track at days 4 and beyond, it is too early to be confident in the wind speeds, rainfall amounts, or any impacts this storm may bring to the islands,” forecasters said.
Iselle is expected to remain a major hurricane for at least a couple more days as it crosses into the Central Pacific and should gradually weaken into a tropical storm as it approaches Hawaii.
Iselle should also bring some surf to east and south shores before it arrives in Hawaii.
Behind Iselle, the tenth tropical storm of the busy Eastern Pacific hurricane season formed Sunday, and could also be on a path towards Hawaii.
Tropical Storm Julio is moving west near 16 mph and was located about 1,065 miles southwest of Baja, California at 5 p.m.
Sustained winds are at 60 mph, but forecasters say it could strengthen into a hurricane by Wednesday before weakening as it moves over cooler waters.
Forecasters are monitoring the storm and say it could bring more rain to Hawaii starting Saturday.