Tropical Storm Lane continued a weakening trend overnight as the mountainous and rugged terrain of the Hawaiian islands ripped apart the former Category 5 hurricane.
Despite the downgrade to a tropical storm, Lane continues to produce catastrophic amounts of rain on the Big Island of Hawaii, where flash flooding and mudslides have forced numerous road closures, evacuations and swift-water rescues. At least four weather stations on the Big Island have reported more than 40 inches of rain since Wednesday afternoon.
And there is still a lot more rain on the way. By the end of the weekend, Lane may become the wettest tropical system to affect the United States, breaking a record set a year ago when Hurricane Harvey dropped 60.58 inches of rain in Port Harvey, Tex.
Lane was downgraded to a tropical storm at 2 p.m. Hawaiian time (8 p.m. Eastern) on Friday after the storm underwent rapid weakening when it encountered an unfavorable environment as the center of circulation approached the islands. As of 11 a.m. Eastern time Saturday, Lane had maximum sustained winds of 60 mph and was about 110 miles southwest of Honolulu, moving north at 3 mph.
Lane will probably lose its tropical-storm status sometime in the next 36 hours. But the storm will continue to produce immense rainfall through the remainder of the weekend, with an additional 10 to 30-plus inches of rain possible for parts of the Big Island.
The island of Oahu, home to Honolulu and 70 percent of Hawaii’s 1.4 million residents, has not experienced the same severity of effects as the Big Island so far. Five to 10 inches or more of rain, the bulk of which will fall in the next 36 hours, is expected in and around Honolulu.
Devastating rainfall totals on the Big Island
With rain bands enhanced by the sloped terrain on the east side of the Big Island, Lane has produced some jaw-dropping rain totals. Hilo, on the northeast side of the Big Island, recorded 15 inches of rain on Friday, making it the fifth-wettest day on record for the city. Hilo has received 31.85 inches of rain since Wednesday, marking the wettest three-day period recorded. The combination of terrain-enhanced rain bands and a slow-moving storm system means that a lot more rain will probably fall on the Big Island.
Dramatic destruction of Lane caught on satellite
On Friday afternoon, satellite imagery captured a fascinating and rapid weakening of Lane as the storm approached the Big Island. Tropical systems prefer upper-air wind patterns without any wind shear (the change in wind speed or direction with height). As Lane’s outer bands began to interact with land Friday afternoon, the rugged and steep slopes of the Hawaiian terrain created an environment full of wind shear.
Lane’s center of circulation was essentially split in two, with a surface-based center of circulation south of Hawaii and a midlevel circulation moving in an opposite direction toward the northeast. This “decoupling” of the two centers of circulation is the mark of death for tropical systems, but as the deluge on the Big Island exemplifies, weakened tropical systems can still be dangerous.