Hawaii to face flooding downpours, mountain snow this week

By Jordan Root, AccuWeather meteorologist
November 27, 2017, 11:40:17 PM EST

The threat for flash flooding and landslides will increase this week across Hawaii, and residents and vacationers will need to be on alert.

A plume of deep tropical moisture is expected to surge northward to Hawaii this week and will provide the fuel for heavier and more frequent downpours for some of the islands.

“The first round of heavy rainfall is expected through Tuesday, with torrential downpours focusing on the Big Island and Maui,” AccuWeather meteorologist Faith Eherts said.

Stronger-than-normal northeasterly trade winds will blow across the islands and up the windward slopes, and will combine with the deep tropical moisture to trigger very heavy rainfall.

Hawaii downpours 11.27 AM

“Rainfall rates of up to 2 inches per hour can result in dangerous flash flooding as well as landslides, which could topple trees and power lines and block or wash out roads,” Eherts warned.

Rainfall amounts of 3 to 6 inches are expected for Hilo and other windward coastal areas into midweek, with higher amounts farther inland across the Big Island and Maui.

It will be cold enough across the summits of Mauna Kea and Mauna Loa for heavy snowfall during this time. A few inches are expected with localized amounts of up to a foot possible.

Hikers will need to be vigilant and keep a close eye on weather conditions.

While rainfall amounts will be less on the leeward side of the islands, moisture may wrap around at times and lead to heavier showers.

Hawaii Weather Radar
Dangers of flash flooding
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Molokai, Oahu and Kauai will miss out on the heaviest rain, but a slight uptick in moisture will still bring more numerous and enhanced trade showers over the next few days.

Northeastward-facing coasts will face elevated surf this week thanks to the strong trade winds. Occasional gusts of 30 to 40 mph are in store.

The first part of the week will be very wet across some of the Hawaiian Islands, but the second half of the week and into the weekend could be just as wet, if not wetter.

Deep tropical moisture will remain strung out over Hawaii and there are indications that a storm could develop in the area by Friday. If this were to occur, there could be widespread enhanced showers for some or even all of the islands.

“Another round of heavy rain would exacerbate any existing flooding or bring new flooding problems to the other islands,” Eherts said.

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