Hurricane Nolo Strengthens Toward Hawaii's Big Island, With Forecasters Warning of Up to 35 Inches of Rain

Hawaii's Big Island is under a hurricane watch as Hurricane Nolo strengthens over the Pacific roughly 285 miles south of South Point, with winds now near 80 mph, according to Hawaii News Now's first-alert forecast issued Thursday. The storm is expected to make its closest approach to the island late Friday into Saturday as a high-end Category 2 or possibly a Category 3 hurricane, and while it is not currently forecast to make direct landfall, forecasters say a close pass alone could still deliver Category 1 or Category 2 conditions to parts of the island.

The real danger is rain, not wind

CBS News reports forecasters expect 15 to 30 inches of rain across the eastern and southern Big Island, with isolated totals as high as 35 inches in the steepest terrain, and warns that rainfall of that scale could cause "catastrophic and life-threatening flooding and mudslides". The Honolulu Star-Advertiser notes Nolo strengthened from a tropical storm to a hurricane through Thursday, meeting the threshold that triggered the watch's upgrade, and that the National Weather Service expects the rainfall threat to persist even if the storm's core stays offshore.

A state already worn down

This is Hawaii's fifth major weather or geological disaster of the year, following the Kona Low storms in March, a Hawaii Island earthquake in May, and Hurricanes Lala and Lowell over the summer, a run of events that has already left an estimated 686 million dollars in damages across the state. Emergency managers on the Big Island, still working through recovery from the earlier storms, are treating Nolo's rainfall forecast as the more urgent hazard than its wind speed, since mudslide-prone terrain that has already been saturated by earlier storms this year is more vulnerable to a repeat soaking than it would be in a normal, drier year.

What residents are being told

County officials have not yet ordered mandatory evacuations as of Thursday, and the storm's exact track over the coming 48 hours will determine how much of the rainfall total lands over populated areas versus open ocean. Weather.com's Friday update advises residents in flood-prone and steep-terrain areas of the Big Island to prepare now rather than wait for the storm's closest approach, given how quickly heavy tropical rainfall can turn into flash flooding on the island's volcanic terrain.