Drenching rain unleashed tons of mud, rock and trees across the Pali Highway yesterday morning, choking one of O'ahu's main arteries yet again and sending commuters into gridlock throughout the day and into the night.

State Department of Transportation crews planned to continue cleaning up the debris outside the second townbound Pali tunnel last night. They hoped to open the Pali Highway this morning to town-bound commuters by contraflowing traffic starting near St. Stephen's Diocesan Center from 4 a.m. to noon.

No schools were scheduled to be closed today because of the weather, the Department of Education announced last night.

Yesterday's combination of heavy, continuous rain, a mudslide that shuttered traffic in and out of the Pali tunnels, and even the possibility of a tornado on Kaua'i and O'ahu, came less than three weeks after two earthquakes rocked the state and helped knock out power.

And it was only two months since O'ahu was choked by gridlock traffic when a military truck crashed into an 'Aiea overpass, shutting down the H-1 Freeway and sending commuters crawling for hours through improvised, alternate routes to get home.

Dennis Lee, 60, was driving his 1984 Toyota Tercel through the Pali tunnels toward town when he found himself behind a line of about 15 cars that were all stopped.

"All of a sudden you could see a lot of clear water, then muddy water and then a lot of rocks," Lee said. "Everyone started getting out of their cars and somebody said there was a landslide."

Lee, who has lived on the Windward side for 18 years, had never seen so much continuous rain and was out photographing waterfalls.

Trapped inside the Pali tunnels about an hour, he walked out into the rain and began shooting photos of the mudslide, which was "as high as a car," he said. "It stretched across the two (town-bound) lanes and over one lane Kailua-bound. We were all stuck."

A 58-year-old woman who had been driving a van when the mudslide fell was shaken up but otherwise unhurt, said Bryan Cheplic, spokesman for the city's Emergency Medical Services department.

The woman was taken to Castle Medical Center in "extremely stable condition," Cheplic said.

Two city paramedics, who were stuck behind the line of cars, hiked a quarter-mile to the scene in the rain to get to the woman, he said, as a third paramedic maneuvered their ambulance through traffic.

No one else needed medical treatment, he said.

Road crews worked to clear the debris — largely mud, rock and trees — through the night.

Workers leave early

Within hours of the mudslide — and a second, smaller mudslide farther Kailua-bound near Kapa'a Quarry Road — Gov. Linda Lingle and Mayor Mufi Hannemann let some government workers off early to go home. Police also sent nonessential workers home early, but kept officers in uniform and many of them on overtime.

Last night, as thousands of drivers navigated through rainy streets to get home, Hannemann asked drivers to stay put if they didn't have to use O'ahu's roads.

"We want people to stay off the road except for those who have to be on the road," Hannemann said. "And exercise patience. Drive with aloha and exercise a lot of caution."

With the Pali tunnels closed, Windward commuters tried to get home through East Honolulu or by heading north and taking the H-3 Freeway or Likelike Highway.

But many were confused and frustrated by an electronic road-work sign on the H-1 Freeway that announced that the Likelike Highway would be closed because of road work.

Many apparently did not see the portion of the sign that said the Likelike would not be closed until Sunday, said Scott Ishikawa, spokesman for the state Department of Transportation.

Some of the heaviest rain fell on the Windward side, where the Wilson Tunnel on the Likelike Highway saw nearly 10 inches in 24 hours.

Weather forecasters saw ominous upper air wind movements during the day, which raised the possibility tornadoes could develop. But no tornado watch or warning was ever issued and by the end of the day that possibility had largely dissipated, said National Weather Service meteorologist Nezette Rydell.

"Flooding is by far the larger threat right now," she said.

Police closed the Kane'ohe-bound lane of Kamehameha Highway in Waiahole Valley and had to contraflow traffic due to flooding.

Drivers could get through, but it was "slow going," said John Cummings, spokesman for O'ahu Civil Defense.

vehicles Stuck in water

Five vehicles got stuck in water and had to be towed out. Police were advising drivers of small cars to stay out of the area.

"It's the usual flooding and ponding that occurs in the area when it gets rain like this," Cummings said.

He urged drivers not to drive across flooded roads or highways anywhere.

"You could get hit by a flash flood," he said. "We don't want that. Turn around, don't drown — bottom line. Even if you have a big truck."

The state Department of Health also was advising people to stay out of streams and coastal waters that turned murky or brown by storm waters and could contain chemicals, microorganisms from overflowing cesspools, septic tanks or animal feces.

Warning signs will go up around waters known to have been contaminated, but health officials want people to be cautious about venturing into storm or standing water — even if no signs are present.

The rains yesterday also caused some anxious moments on Kaua'i, where rivers quickly rose to flood levels as heavy rain ran off soils already soaked from rainfall earlier in the week.

The Hanalei River flooded over Kuhio Highway, stranding residents and visitors throughout the afternoon.

Other streams rose to near flood levels, but no serious flooding was reported. Other than ponding and roadway debris, civil defense authorities reported few problems — despite nearly 9.85 inches of rain at Mount Wai'ale'ale in the 24 hours to 5 p.m. yesterday.

The storm system that drenched Kaua'i and O'ahu was to move over Maui County last night and today before drifting away from the Islands.

"The strongest focus is the middle islands of the state," said the National Weather Service's Rydell. "All of Maui County could see some heavy stuff overnight."

Depending on the speed with which the low-pressure system moves, thunderstorms and heavy rain could continue into the morning before the system moves away.

The Big Island missed most of the rain from the storm system, but did experience some thunderstorms north of Hilo yesterday, and could experience more thunderstorms today, she said.

Rydell said that by late today, the system should have moved on. "We expect it to diminish and pull on out," she said.

However, moist air and light winds could keep conditions wet into the weekend.

"The big trigger will be gone, but it won't suddenly be dry," she said. Trade-wind weather is expected to re-establish itself late Monday.

Civil defense tested

Yesterday's combination of events tested state and O'ahu Civil Defense plans that were still being revisited following last month's 6.7- and 6.0-magnitude earthquakes that were centered off the Big Island.

The regularly scheduled monthly test of Hawai'i's warning sirens yesterday came about an hour after the 10:30 a.m. Pali Tunnel mudslides and caused some worried residents to call state Civil Defense.

"They wanted to know why we're blowing the sirens," said Ray Lovell, state Civil Defense spokesman. "We figured this might happen with the first test after the earthquake. But we've got to test."

The test wasn't without glitches. As state Civil Defense officials were preparing to transmit the simultaneous test warning message to radio and television stations, a contractor inadvertently cut a cable near state Civil Defense headquarters, shutting down the telephone line that transmits the signal.

Civil Defense officials started getting calls from radio and TV stations saying the line appeared to be dead. So state officials told the broadcasters to monitor KSSK radio and pick up the signal on a back-up line that uses radio waves, Lovell said.

"It's working but the audio quality sounds more like it's coming over a telephone," Lovell said. "The system still works."

Both the primary and back-up alert systems were back online and operating by early afternoon.

One school in the state — Kilohana Elementary School on Moloka'i — didn't open due to heavy rain, but no other schools were closed by weather.

Wednesday is an early release day, so once students left at 1:30 p.m., principals on O'ahu and Kaua'i were given permission to dismiss teachers and staff who live in affected areas.

Advertiser writers Peter Boylan, Mike Gordan, Treena Shapiro and Jan TenBruggencate contributed to this report. Reach Dan Nakaso at dnakaso@hono luluadvertiser.com or 525-8085.

Reach Dan Nakaso at dnakaso@honoluluadvertiser.com.