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Hurricane Iselle Downgraded to Tropical Storm

A satellite image reveals tropical storm Iselle bearing down on the Big Island of Hawaii.
(Image credit: NOAA)

As the winds from tropical cyclone Iselle lashed at the Big Island of Hawaii late Thursday evening local time, the storm was downgraded from hurricane status to a tropical storm, according to the National Weather Service's Central Pacific Hurricane Center.

In an updated advisory on Iselle that came at 11 p.m. Hawaii-Aleutian Standard Time, as the storm reached a position about 50 miles (80 kilometers) south of the city of Hilo, the National Weather Service (NWS) also noted that the watches and warnings in effect across the state were not being changed.

The Big Island remains under a hurricane warning, and the rest of the state remains under a tropical storm warning. "Conditions will remain treacherous enough to warrant the continuation of the hurricane warning for the Big Island and its adjacent waters," the NWS said on its website.

The storm was moving west at 10 mph (16 km/h), and had sustained winds reaching speeds of 70 mph (113 km/h), the advisory said. [Hurricanes from Above: See Nature's Biggest Storms]

The difference between a hurricane and a tropical storm is that the winds of a hurricane are stronger. To be considered a hurricane, a storm's winds must reach 74 mph (119 km/h), according to the National Oceanic and Atmospheric Administration. If a storm's winds are between 39 mph and 73 mph (63 to 118 km/h), it is considered a tropical storm.

On the Big Island, about 10,000 customers lost power Thursday night, according to news reports. Downed trees and damaged roofs were reported on the Big Island, and power outages were also reported on neighboring Maui, according to the NWS.

As the storm moves over the Big Island, sustained winds of up to 45 mph (72 km/h) are expected, with gusts reaching up to 70 mph, according to the NWS.

Dangerously high surf as well as coastal and inland flooding are also expected as Iselle continues to make its way west across the state on Friday, according to the NWS.

On the heels of Iselle, Hurricane Julio is also likely to impact Hawaii early next week. That storm is currently about 1,000 miles (1,600 km) east of the islands, and is a Category 3 hurricane, but is expected to weaken as it travels west.  

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Karen Rowan
Karen came to LiveScience in 2010, after writing for Discover and Popular Mechanics magazines, and working as a correspondent for the Journal of the National Cancer Institute. She holds an M.S. degree in science and medical journalism from Boston University, as well as an M.S. in cellular biology from Northeastern Illinois University. Prior to becoming a journalist, Karen taught science at Adlai E. Stevenson High School, in Lincolnshire, Ill. for eight years.