August 7th, 2014

Hawaii Double Threat: Hurricanes Iselle and Julio

Posted at 3:30 PM ET

hawaii-smallHurricane Iselle is poised to become the first hurricane in 22 years to make a direct landfall in Hawaii. According to the Central Pacific Hurricane Center (CPHC), Iselle is located 305 miles east-southeast of Hilo, Hawaii and 510 miles east-southeast of Honolulu, Hawaii. It has already started raining in Hilo and conditions are expected to deteriorate through the day, with the onset of tropical storm conditions this afternoon and hurricane conditions tonight. Trailing Iselle is Hurricane Julio. Julio is presently 1,235 miles east of Hilo, Hawaii. Julio is expected to impact the area shortly following Iselle, but with some uncertainty concerning the expected track and impacts.

With Iselle expected to arrive late Thursday, state officials have warned the public to be prepared for flash floods, mudslides, and power outages, and advised them to prepare seven-day disaster supply kits. Governor Neil Abercrombie signed an emergency proclamation to allow for easier access to emergency funding and personnel. Public schools have been ordered to close on the islands of Maui, Molokai, Lanai and the Big Island, according to the Hawaii State Department of Education. Flight cancellations have also been reported as the state braces for the impending hurricanes.


Track and estimated wind of Hurricane Iselle (left) and Hurricane Julio (right), according to official advisories of the Central Pacific Hurricane Center and the National Hurricane Center. Advisories issued at 11AM EDT (15 UTC) 7 August.

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 for further information.


The last hurricane to make a direct landfall on Hawaii was in 1992 when Hurricane Iniki destroyed more than 1,400 homes in Kauai and claimed six lives.

Meteorological Discussion

It appears that Hawaii will experience its first hurricane landfall since Hurricane Iniki (1992). Hurricane Julio is following a very similar track to Iselle and is expected by the National Hurricane Center (NHC) to pass close and to the north of Hawaii (with a direct landfall scenario still possible). Hawaii has not experienced two hurricanes in succession for the available historical record.

Hurricane Iselle

As of the 5 AM HST (15 UTC) advisory, Iselle carries maximum sustained winds of 80 mph (130 km/hr). Hurricane and tropical storm force winds extend outward from the center of circulation to 35 and 140 miles, respectively. Iselle continues to move west-northwestward along the base of the subtropical ridge.

During the overnight hours, Iselle started to slowly weaken, but probable landfall as a category-1 hurricane can be expected at Hilo. According to the CPHC, Iselle is expected to make landfall at Hilo tonight as a hurricane, and pass the smaller islands into Friday. During this time, Iselle should continue to weaken and affect the remaining islands as a strong tropical storm. Hurricane and tropical storm warnings have been posted to this effect.

Over the past few days, Hurricane Iselle was able to maintain its intensity due in part to its earlier symmetric structure and strength, and also a recent period of relaxed wind shear between two weather systems. Model intensity guidance struggled with this storm, possibly a result of the region of relaxed wind shear (between two weather systems), and perhaps with the earlier remarkable structure of this hurricane.

Hurricane Julio

Hurricane Julio continues to slowly strengthen as it moves to the west at 17 mph (28 km/hr), following the base of the subtropical ridge on a very similar path to Iselle. Maximum sustained winds as of the 5AM HST (15 UTC) advisory are 105 mph (165 km/hr). Hurricane and tropical storm force winds extend outward from the center of circulation to 15 miles (30 km) and 90 miles (150 km), respectively.

According to the NHC, a continued west-northwestward motion is expected to continue over the next 48 hours.

Over the longer term, it is too early to determine the exact track and intensity of Julio as it approaches Hawaii. While a weakness was expected to develop in the subtropical ridge, it appears that this will not be as significant as expected. The result should be a track further to the south than earlier forecast scenarios.

According to the NHC, Julio should pass to the north of Hawaii as a strong tropical storm, and close enough to render impacts. Julio should approach the islands late Saturday and pass them at closest approach during the day Sunday. A more southerly track closer to the islands is still possible, and this would inflict a higher degree of impacts. Interests in Hawaii should closely monitor the progress of this storm.

Expected Hazards and Impacts

Expected hazards and impacts from Iselle include:

Tropical storm wind conditions for Hilo this afternoon, with the onset of hurricane conditions tonight. The remaining islands should experience tropical storm conditions over Maui tonight, Oahu Friday, and Kauai Friday afternoon. 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 powerlines over most of the islands. Weaker and older structures should experience a higher degree of damage.

Excessive surf with large and damaging waves of 10-15 feet (3-5 m), especially for eastern and southern-facing beaches, coupled with a storm surge on the order of 1-3 feet (0.3 m to 1 m). Property on the immediate coast could well experience impacts of a severe nature.

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 can be expected as a result, posing a threat to life and property.

The impacts of Julio and their severity will depend on how close the storm comes to 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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Guy Carpenter publishes CAT-i reports for major natural catastrophes worldwide. These reports cover catastrophes including worldwide tropical cyclones, earthquakes, major UK and European floods and any other natural event that is likely to incur a significant loss to the (re)insurance industry. Please email if you wish to be added to the free email distribution list.

Guy Carpenter compiles RISK-i reports for major technological or man-made events worldwide. These reports cover risks to property, transport and life including explosions, fires, crashes, engineering disasters and terrorist attacks that are likely to incur a significant loss to the (re)insurance industry. Please email if you wish to be added to the free email distribution list.

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