Hawaii Island Drops Hurricane Watch as Nolo Tracks West With 90 mph Winds

Q: With Nolo moving away, why are experts still warning of life-threatening 25-inch floods and mudslides on the Big Island?

Experts are still warning of life-threatening flooding because the danger on the Big Island comes less from a direct hit by Nolo’s eye than from its rain bands, slow movement earlier in the day, and Hawaii’s terrain. Forecasters said Nolo lingered south of the island before beginning its westward move, allowing outer bands of tropical moisture to keep training over the same areas. Even as the center pulls away, those bands can continue dumping intense rain, especially across the island’s eastern and southern slopes. The Central Pacific Hurricane Center said additional rain of several inches is still expected, bringing storm totals to 10 to 20 inches, with isolated spots reaching 25 inches. The Big Island’s steep mountains make that far more dangerous. Moist air is forced upslope, which can sharply increase rainfall rates. In narrow valleys, gulches and drainage channels, water can rise quickly, triggering flash floods. Saturated hillsides are also more likely to fail, raising the risk of mudslides and rockfalls. Officials are especially concerned because some of the same southeastern areas were hit hard by recent storms and the ground is already wet in places. That reduces the land’s ability to absorb more water and increases runoff. So while the hurricane watch has been dropped, the flood threat has not. That is why the tropical storm warning, flood watch, road closures, and shelters remain in place even with Nolo moving away.

3 articles · Updated · Hawaii Tribune-Herald · Sep 26

Hawaii Island's hurricane watch was canceled after Nolo began moving west away from the island, though a tropical storm warning and flood watch remained in effect Friday afternoon.
At 11 a.m., Nolo was 160 miles south of South Point with 90 mph sustained winds, moving west at 5 mph; hurricane-force winds extended 35 miles from the center and tropical-storm winds 150 miles.
Forecasters said the storm should stay well south and southwest of the main Hawaiian Islands, with models agreeing it will be clear of the chain before turning west-northwest early next week.
Nolo is still expected to strengthen into a major hurricane this weekend, peaking near 130 mph south-southwest of Kauai late Sunday night before weakening and passing far west of Kauai by Tuesday.