Kona low to be double-edged sword for Hawaii

This image of the central Pacific Ocean, with Hawaii near the middle, shows a vast area of stormy conditions on Friday, Dec. 1, 2023. (AccuWeather Enhanced RealView™ Satellite)

Trouble is brewing in paradise, AccuWeather meteorologists say. Residents and vacationers across the islands of Hawaii will continue to be drenched by rounds of heavy rain through the rest of this week as a feature referred to as a Kona low is expected to continue circulating over the islands. Heavy snow will pile up on the summits of the Big Island.

A Kona low is an area of low pressure that typically sets up to the west or northwest of the state and ushers in south-to-southwest winds across the Hawaiian Island chain, spreading tropical rain across the region. The south-to-southwest winds starkly contrast the prevailing east-northeast trade winds that occur most often.

The term "Kona" is a Hawaiian word that means leeward and describes winds with a southerly component across the region.

"A huge storm was in place across the Aleutians last week, and pieces of energy from that storm broke off and are now camped west of the Hawaiian Islands," explained AccuWeather Meteorologist Joseph Bauer.

Bauer added that this storm has led to the development of low pressure in the region, which is pulling enhanced tropical Pacific moisture over the islands into this weekend.

The drenching rainfall will continue across Hawaii into the start of the weekend, which may help improve the ongoing drought conditions. However, improvements to the drought will come at the expense of flash flooding.

Along with the downpours will be the risk of flash flooding, road washouts and debris flows, especially in recent burn scar locations.

Rainfall amounts could range from 2-3 inches across portions of the western islands, with locally higher amounts across the south- and southeast-facing slopes of the higher terrain across Kauai and Oahu due to the southerly flow.

As of Friday morning, some of the top rainfall amounts on part of the Big Island range from 6.36 inches at Hilo to 14.81 inches at Pahoa, Hawaii. Meanwhile, Honolulu has picked up about 2 inches of rain thus far from the storm, which is only about 0.25 of an inch under the entire month's worth of rain in November.

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"This enhanced moisture will strengthen usual shower and thunderstorm activity in the region, leading to localized areas of flooding, mudslides and debris flows, especially in areas recently affected by wildfires," explained Bauer.

Statewide flood watches were issued late Monday night for heavy rainfall expected through Thursday afternoon.

Excessive runoff from the higher terrain could cause streams to overflow and result in road closures. Residents in urban areas may face rapid runoff that can even cause property damage and significant flooding.

The wettest period is expected to continue across the region through the end of the week. However, rain and thunderstorms can also linger across the western islands on Saturday.

Conditions can become breezy at times, but the strongest winds are expected to stay offshore to the northwest. Through late week, boaters and mariners should exercise caution in this zone north and west of Oahu and Kauai, especially if operating small craft.

The air is cold enough for snow to fall on the summits of the volcanos on the Big Island, which tower just over 13,000 feet above sea level.

Rounds of heavy snow, including near-whiteout conditions, have occurred. The summit of Mauna Kea has picked up several inches of snow thus far, with blowing and drifting snow as well.

A webcam shows snow on the summit of Mauna Kea, Hawaii, on the morning of Nov. 30, 2023. (Japan Hawaii Observatory)

Although West Maui opened back up for tourism on Nov. 1, locations in Maui County that were impacted by the devastating Lahaina wildfire last August are still struggling to rebuild properties, Hawaii Gov. Josh Green told NewsNation.

Drought conditions across the Hawaiian Islands range from moderate to extreme levels, according to the U.S. Drought Monitor.

Forecasters say that the rainfall expected this week may provide minor improvements to the Hawaii drought but may not entirely diminish the dry conditions.

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