A powerful and slow-moving storm was inching across Hawaii on Wednesday, bringing an extended period of heavy rain, thunderstorms and strong winds that could last into early next week. Forecasters said flash flooding and downed trees and power lines were possible across the state, and significant snowfall was likely on the summits of the Big Island.
The storm, known as a kona low, is a major weather maker in the Hawaiian Islands. On Tuesday, the Honolulu office of the National Weather Service said a “high-impact weather event” was beginning to unfold, as the system strengthened northwest of the state, drawing in very moist tropical air northward toward Hawaii.
Flooding concerns had already begun for the western end of the state, in Kauai and Oahu, where forecasters said rainfall rates reached up to two inches per hour on Tuesday.
The flood threat is expected to grow as the week progresses. Repeated rounds of rain and thunderstorms could produce intense rainfall rates, as the storm is expected to slowly spread eastward across the rest of the smaller islands by midweek, before reaching the Big Island toward the end of the week.
Flood watches, which mean flooding is possible, were issued for Niihau, Kauai, Oahu, Maui County and the Big Island through Saturday afternoon. Forecasters warned that streams and drainage systems could overflow, potentially leading to road closures, property damage and landslides.
Forecasters also said severe thunderstorms were possible, especially on Friday and Saturday, and could bring strong winds, large hail and even a tornado.
In addition to the threat of severe storms and flooding, strengthening winds are expected to be another hazard later in the week, especially across the summits of the Big Island, where gusts exceeding 100 miles per hour are forecast by Saturday. A high wind watch was issued from Thursday evening through Sunday afternoon. Forecasters said the powerful winds could bring down trees and power lines.
On the highest peaks of the Big Island, winter weather is also expected. Forecasters said cold air associated with the storm could allow heavy snow with significant accumulations on the summits later in the week, and during the weekend. A winter storm watch from Thursday evening through Saturday afternoon was issued for areas above 12,000 feet, where total snow accumulations of eight inches are possible.
Nazaneen Ghaffar is a Times reporter on the Weather team.
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