Post-Christmas rain floods Kaupo, sets record in Hilo

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KAHULUI - An upper-level low-pressure system moving in from east of the Big island combined with a strong trade wind flow to generate heavy showers on Maui and the Big Island on Thursday and Friday.

Hilo Airport reported record high rainfall for Dec. 26, with 5.25 inches recorded by 5 p.m. - and rain still falling. The old record was 3.74 inches set in 1981.

But Maui rain gauges matched the flow, with the Kaupo Gap recording 7 inches of rain as of 5 p.m. Friday, while Oheo Gulch, also on the remote east end of Maui, received 4.38 inches.

The downpour on the east end of Maui forced the closure of the Kaupo Road at Pahihi Gulch, where flooding made the road unsafe, according to a Maui County statement issued at 9 a.m. Friday. The road will remain closed indefinitely, the county said.

If the windy, wet conditions kept people off the beaches, off whale watch cruises and off the road to Kaupo, it led to crowds at shopping centers and at the Maui Ocean Center at Maalaea.

At the Ocean Center, marketing director Lori Mellenbruch estimated more than 2,000 visitors stopping in, leading to a line or more than 100 waiting for admission early in the afternoon - when the sun was out.

"The line can definitely form when there's wind and there's rain, and the boats are canceled," she said. "Our Number One competition is the beach."

The center is open from 9 a.m. to 5 p.m., but admission peaks between 10 a.m. and 2 p.m.

It will likely be a good place to visit through the weekend, with Maui weather analyst Glenn James saying the stormy conditions are expected to continue into Monday.

James, senior weather analyst with the Pacific Disaster Center, said the heavy rain is generated by strong trade winds from a high-pressure system northeast of the islands combining with the upper-level low that is augmenting the surface moisture carried in on the trade wind flow.

"There's a low pressure area aloft that we've been tracking all this week, coming out of the east of the Big Island, while the surface trade winds are coming from the northeast. For the last five, six days, they've been marching in our direction, arriving at the same time," he said.

"The combination is a one-two punch, with strong, wet trade winds and this upper-level low that has enhanced greatly the rainfall on the windward sides."

The wind has been blustery enough to push the wet conditions over to leeward areas, bringing significant rainfall to Kihei, Kula and Ulupalakua.

"With the upper low, you are bringing in cold air aloft with the lower-level trades bringing in moisture on the surface. The combination of the warm moist air off the ocean and the cold air aloft creates instability," he said.

While the upper low is moving west and weakening, it will continue to generate clouds and showers before it moves away. Even after it passes, James said the trades will continue to bring in windward and mauka showers.

He said it was too early to predict the conditions for New Year's Eve on Wednesday, although preliminary forecasts indicated southeasterly winds during the day and only light trades at night.

On Friday, the trades were pumped up to a high of 46 mph on Kahoolawe, 33 mph in Maalaea Bay and 29 mph at Kahului Airport.

On the Haleakala summit, winds were blowing 25 mph with a peak gust of 44 mph at 3:30 p.m. With overnight temperatures expected to fall below freezing, summit roads were expected to be icy today, with more than 3 inches of rain recorded Friday.

James produces the www.hawaiiweathertoday.com site, which will have updates on Maui weather conditions through the weekend.

* Edwin Tanji can be reached at citydesk@mauinews.com.

* This story includes a correction in the spelling of Lori Mellenbruch.