Moisture Stuck Over Big Island, 6 Inches Over Parts of Maui

Photo by Seth Welcker. Trees and electric lines down on the Kula Highway past the ʻUlupalakua General Store block access to transmitter sites for two Pacific Media Group stations that were knocked of the air by the storm. 8/8/2014.

By Wendy Osher

(Update: 9:22 a.m.; 7 a.m. 8/8/2014)

What’s left of the center of tropical storm Iselle has moved offshore, southwest of the Big Island, and continues in a WNW motion.

The system was last tracked passing south of Maui County at 8 a.m. and was moving WNW at 20 mph, with maximum sustained winds near 50 mph.

Mike Cantin with the National Weather Service said Iselle still remains a threat.

“That’s what I’m trying to emphasize out there — that as folks wake up and it seems a little breezy and there are some showers out there, the idea is that we could still get these  sudden gusts, and still the potential for flooding. There is still some deep tropical moisture out there and as it moves further west, the moisture will transition off the Big Island and begin to work its way further west,” said Cantin in a morning press conference.

“Some areas on the windward side of the Big Island have gotten in excess of 11 inches of rain already, and it’s still raining, so there will be some locations that get well over a foot of rain on the Big Island,” said Cantin. Elsewhere, he said, we’re still looking at about 5 to 8 inches in Maui County and on Oʻahu.

According to Cantin, up-slope areas of windward Maui and the slopes of Haleakalā have picked up about six inches of rain already, and it is still raining up there.

On the Kula Highway, past the ʻUlupalakua General Store, trees and electric lines blocked access to a transmitter site for two radio stations run by Pacific Media Group that were knocked off the air by the storm.

“I think rainfall is going to be the big threat as we move ahead with this, and those sudden wind gusts which can still do damage to roofs, power poles, power lines, cause power outages, and other issues,” he said.

Timing wise, it looks like the strongest potential gusts are mid-day for Oʻahu, through about that time for Maui; and for the Big Islands the winds have really dropped off, but it’s just the rain now,” said Cantin.

“We’re seeing that a lot of the moisture is being stuck over and wrung out over the Big Island. It appears — I’ve heard a lot of folks saying — that it looks like it’s hung up over the Big Island.What’s happening is the center is moving away, but all the moisture is being wrung out. It still is moving west — it’s just that the moisture is stuck in place,” he said.

According to Cantin, the outer edge of the circulation is impacting Maui County now and approaching Oʻahu. “We’re expecting winds on Oʻahu to increase as we head towards late-morning, midday. What we’re seeing away from the center is generally wind gusts — the highest wind gusts in the ballpark of 35 to 45 mph, and maybe some spots up to 50 mph where it’s the strongest. We expect that to be the case as we go through midday and it approaches Oʻahu, the storm will be to the south, but that swath of wind will come by,” said Cantin.

“Sustained winds are generally maybe 25 to 30 mph, maybe up to 35 in some real windy areas. But otherwise, it will be more gusty and associated with terrain where the winds funnel down through valleys, up and over the Koʻolaus, around the channels, around the sides of the islands, and also with the showers. If you get a heavier shower, it’s going to help mix down and bring down the winds from above. So you can get these gusts along with rain. That’s going to be the story as we go through the rest of today for Maui County and Oʻahu,” said Cantin.

For Kauaʻi, if Iselle stays on its current track far enough to the south, there may not be that much of an issue as far as wind and rainfall amounts on Kauaʻi, according to Cantin.

“We’ve already dropped our rainfall amount expectations, which are now down to 3-5 or 3-6 inches for Kauaʻi. If it stays south, there may not be as much of an impact for the folks on Kauaʻi and Niʻihau,” he said.

Additional forecast update issued by the National Weather Service at 9:22 a.m. HST on Friday, Aug. 8, 2014:

SURF IS PEAKING AT HAZARDOUS LEVELS OF 15 FEET THIS MORNING ALONG
THE EXPOSED WINDWARD COASTS. SOME SOUTH FACING SHORES WILL SEE