Iselle regains strength, hurricane warnings issued for Big Island of Hawaii

Thursday, August 7, 2014, 9:14 AM - Hurricane Iselle is taking aim at Hawaii and the window of time to prepare is dwindling.

A hurricane warning has been issued for the main Hawaiian Islands, the first time since Hurricane Fernanda in 1993.

"If Iselle holds together as a hurricane and makes landfall within the islands, it would be the first hurricane to do so since 1992's Hurricane Iniki," says weather.com.

Against what was originally predicted, forecasters say Iselle isn't slowing as it approaches Hawaii.

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The storm loomed about 560 km east of Hilo early Thursday, with sustained winds 135 km/h.

"The onset of tropical storm conditions is expected on the Big Island of Hawaii this afternoon with hurricane conditions expected tonight," says the Central Pacific Hurricane Center in Honolulu. "Tropical storm conditions are expected over Maui County tonight and for Oahu late tonight and Friday."

Very large and damaging surf if also expected to rapidly build along the east and south shores on Thursday continuing into Friday.

Up to 200 mm of rain are expected along the track of Iselle with isolated maximum amounts of 300 mm, the centre warns.

"These rains could cause life-threatening flash floods as well as rock and mud slides."

Governor Neil Abercrombie already signed an emergency proclamation in advance of Iselle and Hurricane Julio, which isn't far behind.

It is expected to slowly strengthen and pass north of the Big Island sometime over the weekend.

MTSAT-2 and GOES-15 imagery of Halong, Genevieve, Iselle and Julio spanning 6,500 miles across the Pacific. pic.twitter.com/65fkl73T3Y

— NOAA Satellites (@NOAASatellites) August 7, 2014

Officials say the two approaching storms within days is extremely rare.

"Dating to 1949, there is only one case where tropical cyclones with direct impact were even 10 days apart," said Kevin Roth, lead meteorologist at The Weather Channel. "That happened in 1982, when what had become Tropical Depression Daniel on July 22 was followed by Tropical Storm Gilma, which brushed the southern tip of the Big Island on Aug. 1. Incidentally, later that season, Hurricane Iwa tracked just west of Kauai in late November and caused an estimated at $234 million in damage."

Roth says a pair of tropical cyclones directly affecting Hawaii in just two to three days' time "is unprecedented in the satellite era," weather.com adds.

Many in Hawaii aren't taking any chances and stores say they are re-stocking shelves as frequently as possible. 

According to Costco's assistant general manager in Honolulu however, they're having a tough time keeping up with essential supplies. 

"This one seems to be a little bit busier than normal just because of the severity of the one and the one right after it coming," says manager Scott Ankrom. "But it always comes as soon as you see that something's coming. Usually the three or four days beforehand, everybody rushes because they realize just how prepared they really aren't."

As of early August, the eastern Pacific had already spawned 10 named storms, says weather.com, including three Category 4 hurricanes.

"On Aug. 4, Iselle became the season's third Category 4 eastern Pacific hurricane."

With files from CNN