Hurricane Iselle

Landfall | Summary
Posting Date: August 8, 2014, 1:30:00 PM

Iselle, the first tropical storm to hit the Big Island since 1958, was downgraded yesterday after forming off the coast of Central America last week. The storm made landfall along the Kau coast on the Big Island, east of Pahala (population 1,378) at 2:45 a.m local time (12:45 UTC), with sustained winds of 60 mph. As of the Central Pacific Hurricane Center’s (CPHC) 5:00 a.m. HST advisory today, Iselle is located 75 miles west-southwest of Hilo. Satellite imagery and other data suggested that Iselle no longer has a discernable eyewall. The storm has slowed and is now moving at 13 mph in a westerly direction and packing maximum sustained winds of 50 mph.

Large and destructive waves are expected to batter a long stretch of coast, creating the potential for widespread coastal flooding. The U.S. Coast Guard has closed several ports, including ones in Oahu, Maui, Molokai, Lanai and the Big Island. A tropical storm warning is in effect for the Big Island and Maui County, including Maui, Molokai, Lanai, and Kahoolawe islands, Oahu County and Kauai County, including Kauai and Niihau islands. All of the Hawaiian islands are under a flash flood watch today.

Exposure at Risk

Iselle made landfall along the Kau coast; the coastline in this region is dotted with hotels, although it also includes vast areas that are sparsely populated. Thus, the exposure value in this region is relatively low.

Iselle’s tropical storm–force winds at landfall could have caused more damage had they impacted a more densely populated location. Structural damage to non-engineered buildings is possible, particularly to roofs—while windows and the cladding on engineered structures could be damaged by impact from debris. Most insured residential structures on Hawaii’s west coast are made of wood, with about 40% of these being single-wall wood frame construction. Generally, load-bearing walls in these buildings are made of thin plywood boards and thus are quite susceptible to wind damage. Wind damage is likely to be limited to roofs, signage, traffic lights, and trees.

Reported Impacts

In advance of the storm, approximately 1,200 people were evacuated from coastal locations likely to be impacted by destructive waves. Authorities warned people in the area to consider making flight plans before airport travel was disrupted. Although the international airport in Honololu is still open, nearly 50 flights in and out have been cancelled. The Governor of Hawaii issued a declaration of emergency yesterday.

Schools are closed on the Big Island, Maui, Molokai, and Lanai, and all state offices are closed today. The state’s primary election is expected to continue as scheduled tomorrow. According to local officials, most of the state’s official polling places are also serving as emergency shelters.

The storm brought heavy rain and high winds to communities in the Big Island and parts of Maui County. Total precipitation on the windward side of the Big Island reached 11 inches in 24 hours. There are currently more than 20,000 customers without power. In Hawaiian Paradise Park, there were reports of damaged roofs and uprooted trees.

A threat of high surf remained throughout the day yesterday and into this morning along eastern shores, with swells peaking yesterday afternoon. The Big Island received surf as high as 16 feet, and Maui was expected to see waves as high as 12 to 18 feet.

Forecast Track and Intensity

The interaction of Tropical Storm Iselle with the mountainous terrain in the interior of Hawaii is producing heavy precipitation over much of the state. Iselle is expected to produce 4 to 8 inches of rain over all of the Hawaiian islands—with as much as 12 inches possible in isolated areas. Over the next few days, these rains are likely to result in flash floods and mudslides. Also, a dangerous storm surge will raise water levels by as much as 10 to 15 feet above normal tide levels along the south-facing coasts.

Iselle will maintain its present movement and pass over Maui and Oahu later today. As the storm interacts with the mountains of Mauna Loa and Mauna Kea, the CPHC forecast expects it to decay rapidly. It will begin dissipating due to drier air and increasing wind shear.

AIR does not expect significant insured losses from this event, primarily because of the region's relatively sparse population and preparations in advance of the storm. However, given the unique nature of the storm, AIR is dispatching a damage survey team to Hawaii to collect more information. The information contained in this and past NewsALERTs is available on the ALERT website.

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Posting Date: August 8, 2014, 1:30:00 PM