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Lane weakens to tropical storm, but may unleash ‘major flooding’ into the weekend

Heavy rain fell on Hawaii on Aug. 23, resulting in flooded residential streets as Hurricane Lane approached Oahu. (Video: Drea Cornejo, Amber Ferguson, Melissa Macaya/The Washington Post, Photo: Getty Images/The Washington Post)

(This article, first published at 11:30 a.m., was updated at 11:30 p.m. based on the latest conditions.)

11:20 p.m. update: Lane has been downgraded to a tropical storm due to strong wind shear which has disrupted its circulation. Positioned about 150 miles south of Honolulu, its peak winds have dropped to 70 mph. The hurricane warnings for Oahu and Maui have been downgraded to tropical storm warnings.

Hurricane-force winds are no longer anticipated from the storm. However, tropical-storm-force winds are still likely. As has always been the case with this storm, very heavy rainfall and flooding are the greatest concerns.

“Excessive rainfall remains possible into the weekend, which could lead to additional flash flooding and landslides,” the Central Pacific Hurricane Center said in its latest advisory.

Original post

Nearly three feet of rain have fallen on Hawaii’s Big Island as Hurricane Lane unloads an unrelenting deluge. The downpours have spread over Maui, Oahu and Kauai, where conditions are predicted to further deteriorate.

The Central Pacific Hurricane Center reported “catastrophic flooding” on the eastern side of the Big Island early Friday and forecasts “additional major flooding and landslides” into the weekend.

Extreme rainfall brought flooding to parts of Hawaii as Hurricane Lane drenched the Big Island. (Video: Taylor Turner/The Washington Post)

Over some of Hawaii’s high terrain, rainfall totals could top 40 inches.

In addition to the extreme rainfall, dangerous surf conditions and strong winds are likely as the powerful storm tracks closer to the Hawaii’s central islands.

However, it has become likely Lane will remain offshore, rather than striking the islands head-on. That said, the storms effects are expected to be serious and officials are urging residents not to let their guard down.

“Regardless of whether Lane makes landfall, severe impacts are still possible and the effects can extend far to the north and east of the center of Lane,” the hurricane center said.

The latest

The Category 2 hurricane, packing winds of 105 mph, is positioned about 150 miles south of Honolulu and is crawling north at just 5 mph.

Over the last 12 hours, the storm has become increasingly disorganized. Its well-defined eye has collapsed, and the storm has morphed into an assymetric blob. As a result, the peak winds are on a down trend, which is expected to continue. Rain – more than wind – has proven to be the storm’s greatest menace, so far.

The Big Island’s Hakalau Station, in the mountains west of Hilo, has registered over 33 inches of rain. A flash flood warning remains in effect for the eastern half of the Big Island, where floodwaters have closed roads and turned mild streams into raging rivers.

Hilo has picked up nearly 20 inches of rain from the storm, pushing its August rainfall total to second most on record.

Rainfall totals on Kauai and Maui have reached as high as 3 to 5 inches, while most reporting stations in Oahu have received less than one inch.

Fanned by tropical-storm-force winds, a brush fire has spread on in Lahaina on Maui, forcing evacuations. At 8:40 a.m., local time Friday, winds in Lahaina were sustained at 37 mph with gusts to 54 mph. A second fire was reported near Kaanapali on Maui.

Peak wind gusts on the islands have reached 35 to 67 mph. Honolulu clocked a gust to 43 mph just before 5 a.m. local time Friday.

Hurricane warnings are in effect for Oahu and Maui, while a tropical storm warning covers the Big Island. Kauai is under a tropical storm watch.

Useful link: Weather radar for Hawaii

The forecast

A day ago, it wasn’t obvious whether Lane would be pulled north and slam into Maui and/or Oahu, or take more of a westerly course, remaining well offshore. It now appears more likely the storm will take the offshore track.

Even so, the turn to the west may not occur until Saturday, and the storm is still edging closer to the islands. In other words, conditions should continue to deteriorate with heavy rain and wind picking up – especially by late Friday afternoon and Friday night in Oahu and Maui. Even if the storm center remains offshore, the islands are positioned to be affected by the storm’s wettest and windiest northwest side.

In Oahu and Kauai, where the storm will be last to depart, conditions may not improve until Sunday or Monday, when the storm should be pulling away.

Useful link: Detailed forecast region by region over Hawaiian Islands from National Weather Service

Over the next 36 hours, at least, dangerous amounts of rainfall are possible.

“Lane is expected to produce total rain accumulations of 10 to 20 inches, with localized amounts up to 40 inches possible over portions of the Hawaiian Islands,” the hurricane center said.

The Hawaiian Islands’ high terrain has a history of being the recipient of some of the world’s most extreme rainfall (one location on Kaui received nearly 50 inches in 24 hours in April). In the case of Hurricane Lane, some areas may receive multiple feet of rain (and some already have).

Useful link: Local hurricane statement from National Weather Service

The storm’s peak winds are on a down trend, which should continue, but if the storm center gets close enough to Maui and/or Oahu, hurricane-force gusts would be possible Friday night, especially in the high terrain and in the upper floors of high-rise buildings.

Should hurricane-force winds materialize, they would result in “considerable roof damage to sturdy buildings,” severe damage to mobile homes, “many large trees snapped or uprooted,” “impassable” roads, and power outages, the Weather Service said.

However, there is a higher probability of tropical-storm-force winds, which could still cause tree damage, minor structural damage and power outages. These winds, which have already started to affect parts of the Big Island, Maui and Oahu, may affect Kauai by Friday night or Saturday.

As the storm churns to the north-northwest, it will also push massive waves into the coastline.

“Surf heights for the Big Island are forecast to range from 10 to 15 feet along the southwest facing shores, with 6 to 10 feet for east facing shores,” the National Weather Service said.  “Surf heights for Maui County, Oahu and Kauai County will rise 15 to 25 feet by [Friday] afternoon.”

The battering waves are expected to bring “significant beach erosion and overwash onto vulnerable coastal roadways through Saturday as Lane makes its closest approach, particularly around the time of the normal high tide cycles,” the weather service added.

Lane: A historic hurricane in the Central Pacific

As it moved within 300 miles of the islands, Hurricane Lane became the closest Category 5 storm on record to approach Hawaii before it began to weaken. The next-closest storm of such strength to approach the islands was John in 1994.

It is only the sixth storm to reach Category 5 intensity in the Central Pacific on record, joining Patsy (1959), Emilia (1994), Gilma (1994), John (1994) and Ioke (2006).

The storm’s central pressure dropped as low as 929 millibars, making it the most-intense hurricane (as measured by pressure) since Patricia in 2015 in the eastern half of the North Pacific Ocean.

In large part due to Lane, the Northeast Pacific Ocean has generated the most Accumulated Cyclone Energy, a measure of storm intensity and longevity, on record for the month of August.