Hurricane Iselle weakened slightly Monday afternoon as the Category 4 storm churns some 1,150 miles east-southeast of the Big Island. Iselle is expected to reach the Big Island as a tropical storm on Thursday evening.
The hurricane was packing maximum sustained winds around 135 mph and was located 1,150 miles east-southeast of Hilo as of 5 p.m. Monday, Central Pacific Hurricane Center forecasters say. Iselle is moving west at 8 mph and is expected to cross directly over the Big Island as a tropical storm starting after 5 p.m. Thursday.
“Iselle is a credible threat (to the Hawaiian Islands) and people do need to think about preparing for the chance of strong winds and wind-driven rainfall,” Forecast Meteorologist Tom Birchard said. “People definitely want to be prepared.”
Birchard said models currently indicate a 44 percent chance of damaging tropical storm force winds affecting Hilo and a 40 percent chance of tropical storm force winds in Kailua-Kona starting Thursday and continuing into Friday. Tropical storm force winds range between 39 and 73 mph.
There is a 2 percent chance of hurricane force winds — wind speeds of 74 mph or greater — for Kailua-Kona and a 3 percent chance of hurricane force winds for Hilo, he said. The center plans to launch on Tuesday a reconnaissance aircraft to sample the environment in and around the storm to provide additional information for forecast models.
In addition to damaging winds and flash flooding, Birchard said the storm will generate large surf along the Big Island’s east-facing shores starting as early as Wednesday evening.
The Central Pacific Hurricane Center, which is based in Honolulu, will begin issuing watches and/or warnings about 48 hours in advance of damaging winds and heavy rain reaching the islands, he said.
Iselle is expected to continue moving toward the west Monday evening before making a turn toward the west-northwest on Tuesday. The storm is expected to gradually weaken during the next couple of days as it encounters wind shear near the Hawaiian Islands.
Hurricane force winds currently extend outward up to 35 miles and tropical storm force winds extend outward up to 105 miles, according to forecasters.
Hurricane Iselle is expected to cross into the Central North Pacific Basin Center, which is located between 140 degrees west longitude and the International Dateline, on Tuesday morning. Both the Central Pacific Hurricane Center and National Hurricane Center are currently issuing advisories on the storm. Once Iselle enters the Central North Pacific Basin, the Central Pacific Hurricane Center will assume sole responsibility for issuing advisories and forecasts.
After Iselle passes the Hawaiian Islands, Birchard cautiuoned that another system, Tropical Storm Julio, is expected to arrive on Saturday or Sunday. For more details on Julio, click here.
“After Iselle, we’re not safe,” Birchard said. “Even if Iselle is a near miss, Julio still exists.”
Central Pacific Hurricane Center forecasters are also issuing advisories on Tropical Depression Genevieve, which was located about 1,040 miles southwest of Honolulu at 5 p.m. Monday. The depression is packing maximum sustained winds near 35 mph as it moves west-northwest around 16 mph.
Forecasters expect little change in Genevieve’s strength on Monday, however, gradual strengthening is expected Monday night into Tuesday, according to the center.
Elsewhere, in the Central Pacific, no tropical cyclones are expected through Wednesday morning.
Central Pacific Hurricane Center officials predicted four to seven tropical cyclones this year in the Central North Pacific Basin. Overall, they give this season an 80 percent chance for a normal to above average number of tropical storms to form.
The Central Pacific hurricane season began June 1 and ends Nov. 30.