Gilma, Hector to approach Hawaii as tropical rainstorms

Gilma, with reduced winds, but still packing rain, will approach Hawaii by the Labor Day weekend and may be followed by Hector just a couple of days later.

Just days after Hurricane Hone passed to the south of Hawaii bringing gusty winds and locally flooding rain, Gilma and Hector are waiting in the wings over the central Pacific with eyes for the islands as well, AccuWeather meteorologists say.

The second and third of the trio of tropical cyclones will make a run at Hawaii within the next week, a feat that is extremely rare.

Gilma is next on the list for this weekend

Gilma peaked as a Category 3 hurricane over the weekend, but winds were slowly on the decline early this week. Tuesday night local time, the tropical cyclone slipped to tropical storm status with 50-mph maximum sustained winds. During the daytime Wednesday, the storm held on to tropical storm strength.

As Gilma tracks over cool water to the east of Hawaii, it will continue to lose wind intensity with some minor fluctuations and become less organized for the balance of the week.

The system will effectively become a squally rain and gale center as it tracks westward in the general direction of Hawaii, perhaps just to the north of the islands. However, even if the center of circulation holds together, it may not be as critical for impacts, as there likely will no longer be a strong eyewall to contend with.

Instead, its gusty showers and drenching thunderstorms will be more spread out and could bring more impacts than a small, compact hurricane.

"One key point to consider even with a poorly organized tropical feature, such as a tropical rainstorm that passes just to the north of the islands, is that some of the south-facing slopes of the islands may get more rain than if a hurricane, such as Hone, was passing by to the south," AccuWeather Lead Long-Range Meteorologist Paul Pastelok said.

While there can be localized flash flooding and mudslides, much-needed rain might occur in hard-to-reach drought areas. Typically rainfall is plentiful on the north- and east-facing slopes of the islands due to the Northeast Trade Winds. The Northeast Trades create a rain shadow effect on the south- and west-facing slopes, which leads to dry brush that is susceptible to catching fire.

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A storm passing by to the north tends to help pull some rain into these arid locations, while a storm passing by to the south just amplifies the Trade Wind effect.

The leading showers and thunderstorms with locally gusty winds will begin on the Big Island late Thursday night or Friday and spread westward over the islands during the course of the Labor Day weekend. Rough seas and surf will precede the rainfall by a day or so as swells from Gilma spread out.

Hector to follow next week

AccuWeather meteorologists are also monitoring another cyclone, Hector, located several hundred miles east-southeast of Gilma. Hector will likely pass over waters that have been churned up and cooled somewhat by Gilma and Hone.

Hector became a tropical rainstorm on Wednesday night, local time, and will remain a tropical rainstorm when it reaches Hawaiian waters Sunday near the Big Island.

Depending on how much of Hector holds together, there may be a significant uptick in drenching showers, thunderstorms and gusty winds from Sunday to early next week, with little pause after Gilma departs. It is possible that Hector passes over or perhaps just to the north of the islands.

At the very least, the close proximity of the two additional tropical cyclones following Hone will tend to keep surf and seas stirred up around the islands from later this week through the Labor Day weekend. The wave action may interest surfers, but the different propagation of the waves from wintertime storms and the prevailing Northeast Trades can create dangerous conditions.

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