Tropical Storm Moke to sideswipe Hawaii with heavy rain, renewed flood risk

Tropical Depression Two-C has gained strength to a tropical storm. Moke will travel close enough to Hawaii to bring enough rain to cause flash flooding on the Big Island later this weekend to early next week.

Hawaii is facing another close call from the tropics just one week after Hurricane Lala passed near the Big Island. Tropical Storm Moke is expected to pass south of the island chain later this week into early next week as a tropical storm or hurricane and will pass close enough to have significant impacts.

"Moke is tracking farther south than Lala did," AccuWeather Lead Hurricane Expert Alex DaSilva said. "However, Moke is a larger storm with showers and thunderstorms currently extending hundreds of miles from the center of low pressure."

As of late Friday morning, HST, Moke was about 660 miles to the southeast of Hilo, Hawaii, located on the northeast coast of the Big Island. The storm was moving along at 10 miles per hour to the west-northwest and could reach hurricane intensity prior to reaching the Big Island's longitude.

"The exact track of Moke and the northward extent of the downpours and gusty squalls as it passes south of the Big Island on Sunday will determine how much rain falls over the island chain," DaSilva said. "Our forecast on that has not changed since we issued it on Thursday, as we factored in both the farther south track and the larger system concept. We will continue to re-evaluate as we see the storm evolve."

The storm has been rated as a 1 on the AccuWeather RealImpact™ Scale for Hurricanes for Hawaii.

It would not take much rain to lead to flash flooding, mudslides and washouts. Despite the forecast of somewhat less intense rain with Moke than with Lala, the ground is still saturated, and some hillsides remain unstable. Some infrastructure, such as roads and drainage systems, remains damaged or clogged with debris.

With Moke, a general 4-8 inches of rain is forecast to fall on the Big Island with local amounts between 8 and 12 inches and an AccuWeather Local StormMax™ rainfall of 24 inches.

Hilo may receive between 2 and 6 inches of rain from Moke. A general 1-2 inches of rain is forecast to fall over much of the balance of the Hawaiian Islands.

If Moke tracks farther south or its downpours stay closer to the center, rainfall totals would be lower. Should the storm drift farther north, heavier rain could fall, especially if Moke strengthens significantly and rain bands intensify.

"It appears that high pressure to the northeast of Hawaii will strengthen a bit and that will send some dry air southwestward," DaSilva said. "That high pressure area is being strengthened by interaction with Lala to the west. The dry air should prevent widespread excessive rainfall on the northern portion of the Big Island and throughout the balance of the island chain."

During the period from Aug. 14-17, Hito received nearly 15 inches of rain associated with Lala, which was nearly 1.5 times their entire historical average rainfall for August.

Parts of the Big Island received between 2 and 3 feet of rain with Lala and a maximum observed rainfall of 43.55 inches. Damage from Lala was extensive on the Big Island with pockets of power outages and pockets of rain- and wind-related damage scattered throughout the islands.

Since the center of Moke is forecast to pass to the south of the Big Island, the strongest wind gusts would likely occur in spiral bands or squalls.

Some gusts on the Big Island, mainly over the higher terrain, will reach between 40 and 60 mph with an AccuWeather Local StormMax™ wind gust of 85 mph.

Even though Moke will pass by well to the south of the islands, swells propagating outward from the center will lead to large breakers on the southeast and southern sides of the islands.

Dangerous surf conditions with strong rip currents are in store with some overwash that will lead to coastal flooding.

AccuWeather RealImpact™ Scale for Hurricanes

In contrast to the Saffir-Simpson Hurricane Wind Scale, which classifies storms by wind speed only, the AccuWeather RealImpact™ Scale for Hurricanes is based on a broad range of important factors. In order to better communicate a more comprehensive representation of the potential impact of a storm on lives and livelihoods, the scale covers not only wind speed but also flooding rain, storm surge and economic damage and loss.

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