Tropical Storm Iselle made landfall at about 2:30 a.m. HST (1230 UTC) today along the Kau Coast on the Big Island, according to the Central Pacific Hurricane Center (CPHC). Maximum sustained winds at landfall were 60 mph, with higher gusts especially at higher elevations. Iselle was moving slowly leading to excessive rainfall accumulations. Resulting flooding has been extensive, together with reports of downed trees and power lines for affected areas. Roads are blocked with debris and downed trees, and power outages have affected at least 33,000. Some roof damage has been reported. There are no reports of deaths or major injuries.
Hurricane Julio has started to weaken from its Category 2 strength. Julio should continue to move to the west-northwest and pass the islands late Saturday and Sunday, according to the CPHC. A direct landfall appears unlikely; however, impacts are still possible for Hawaii if Julio takes a more southerly track.
Forecast track and wind of Tropical Storm Iselle from the Central Pacific Hurricane Center. 11 a.m. EDT (15 UTC) August 8.
Forecast track and wind of Hurricane Julio from the Central Pacific Hurricane Center. 11 a.m. EDT (15 UTC) August 8.
Hazard data illustrated in the CAT-i map was taken from i-aXs®, Guy Carpenter’s web-based risk management platform. i-aXs users can view impacted areas on any map as well as see how their portfolios were affected. Please contact your broker or GC Analytics® representative for assistance or go to www.i-axs.info for further information.
Hazards and Meteorological Discussion
Iselle was downgraded to tropical storm status by the CPHC at 2 a.m. HST (12 UTC). According to the CPHC official advisories, landfall occurred at about 2:30 a.m. HST (1230 UTC) along the Kau Coast on the Big Island, about 5 miles (8 km) east of the town of Pahala. Maximum sustained winds at landfall were 60 mph (100 km/hr), with a central pressure of 1001 mb. Forward motion at landfall was 9 mph (15 km/hr) to the west-northwest. The slow forward speed at landfall has led to excessive rainfall accumulations, with some local reports already exceeding 10 inches (250 mm). As of 4 a.m. HST (14 UTC), the center of circulation of Iselle could no longer be reliably located by radar.
As of the 5 a.m. HST (15 UTC) advisory, Iselle carried maximum sustained winds of 50 mph. Tropical storm winds extended outward from the center of circulation to 105 miles (165 km). Iselle carried a west-northwest motion of 13 mph (20 km/hr), and a central pressure of 1003 mb. With this advisory, Iselle was about 75 miles (125 km) west-southwest of Hilo, and about 180 miles (300 km) southeast of Honolulu.
Iselle continues to weaken due to interaction with the mountainous terrain of Hawaii and a very hostile shear environment. Further weakening is expected by the CPHC, with Iselle expected to degrade rapidly to a post-tropical remnant low as early as Saturday afternoon.
Ongoing hazards from Iselle include:
- • Tropical storm wind conditions for the Big Island and Maui County this morning. Tropical storm conditions are expected on Oahu and Kauai Counties later today. Wind speeds and gusts will be higher with greater elevation in mountainous areas. Light to moderate wind damage can be expected, together with downed trees and power lines over most of the islands. Weaker and older structures should experience a higher degree of damage.
- • Excessive surf with large and damaging waves continues, mainly for east and south facing shores of the Big Island. Dangerous waves of 10-15 feet (3-5 m) are possible today according to the National Weather Service (NWS). This should diminish during the day.
- • Heavy rainfall on the order of 5-8 inches (120-200 mm), with local amounts to 12 inches (300 mm) is expected. Flash flooding and mudslides are an ongoing threat as a result, posing a threat to life and property. Flash flood warnings have been posted by the NWS to this effect.
The hurricane warning for Iselle has been discontinued, but tropical storm warnings remain in effect for all of Hawaii.
Hurricane Julio has started to weaken, and now carries maximum sustained winds of 105 mph (165 km/hr), as of the CPHC advisory of 5 a.m. HST (15 UTC). Julio is now a Category 2 hurricane on the Saffir-Simpson Scale. Hurricane and tropical storm force winds extend outward from the center of circulation to 35 miles (55 km) and 115 miles (185 km), respectively. Julio continues to move to the west-northwest at 16 mph, with a central pressure of 966 mb.
Thanks to dry air and cooler waters, Julio has started to weaken from its earlier Category 3 strength. Increasing wind shear should contribute further to the weakening trend through Sunday.
Julio should continue to follow its current west-northwest motion along the base of the subtropical ridge. Some model guidance solutions have varying expectations on the timing and edge of the ridge, and some actually anticipate a break to develop. The variability of these scenarios continues to bring uncertainty to the expected track of Julio.
The official CPHC track forecast rules out an actual landfall in Hawaii, bringing Julio closest to the islands late Saturday into Sunday as a low-grade hurricane. However, the southern track scenarios bring Julio close enough that impacts could be rendered to the islands including possible tropical storm conditions. Interests in Hawaii should closely monitor the progress of Julio as Iselle clears the islands.
Sources: Reuters, Associated Press, Agence France Presse, U.S. National Weather Service, U.S. National Hurricane Center, U.S. Central Pacific Hurricane Center.
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