Lane now Category 4, rain the greatest threat to Hawaii

Posted: Aug 22, 2018 6:47 PM -04:00 Updated:
Source: NOAA Source: NOAA

After becoming a Category 5 storm early Wednesday, Hurricane Lane has begun to weaken. It is still however a strong Category 4 storm with 155 mph winds as of Wednesday night. Weakening was expected as Lane continues to turn north towards Hawaii. While Lane will continue to weaken the further north that it goes, the issue is that it will pass frighteningly close to all of the main Hawaiian Islands over the next three to four days. Five of the eight largest Hawaiian Islands remain in the forecast cone of concern, including the most heavily populated island of Oahu. Lane will be a weakening Category 1 storm as is makes its closest approach to the capital city of Honolulu on Saturday.

Much of the hurricane force winds with lane are expected to stay offshore, but the storm is large enough that all of the main islands should experience tropical storm force winds. In addition, the tall mountains and narrow valleys on many of the islands will act to speed up winds in localized areas, meaning hurricane force winds are still likely in isolated spots around the state. According to the state of Hawaii, many of the buildings built before the early 1990s on the islands are not designed to withstand hurricane force winds. The damage from even a weak hurricane would be higher in Hawaii than the damage it would have in Florida because of the differences in building code. The winds from Lane will also contribute to a much more dangerous threat.

Much of the annual rain in Hawaii is caused by easterly winds rising up the sides of the dead or dormant volcanoes (and one active one in Kiluea) that make up the islands. These volcanic peaks reach as high as 13,000 feet on the Big Island, 10,000 feet on Maui, and 4,000 to 5,000 feet on Oahu and Kauai. Even though Maui and the Big Island are outside of the forecast cone of concern, they will see just as much if not more rain from Lane than the islands in the cone because of this effect, called orographic lift.

The rain forecast from the storm is a setup for a flooding catastrophe. Rainfall across the islands will range from 10 to 15 inches. Some areas could see up to 20 inches of rain. Deadly mudslides, landslides and flash flooding are likely because of the steep terrain on the islands and the sheer amount of rain forecast. Ultimately the extreme rain will be the most damaging and potentially deadly impact from this storm.

 

In addition to the wind and the rain, high surf will cause damage and tornadoes are possible on the islands as they sit in the strong northeast quadrant of Lane as it passes.

 

A direct landfall from Lane is still possible, and if that does happen the storm would be in rare company. Since 1900 only two hurricanes have actually made landfall in Hawaii, both on the island of Kauai. Hurricane Dot hit in 1959 as a Category 1 and Hurricane Iniki hit in 1992 as a Category 4. Hurricanes are rare here for a couple of reasons. Many systems in the central Pacific pass south of the islands due to strong high pressure that blocks them from curving north there. Even if there is an opportunity for storms to move north such as with Lane, the environment for tropical development is still quite hostile around Hawaii. Substantial weakening almost always occurs before the storms make their closest approach. Iniki in 1992 was a notable exception due to it being a fast moving storm.