Weather Forecast

Hawaii County Weather Forecast for August 16, 2021

August 16, 2021, 7:16 AM HST
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Hilo

Today: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 81 to 87 near the shore to around 72 at 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 65 to 72 near the shore to around 54 at 4000 feet. Southeast winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Tuesday: Mostly sunny with isolated showers in the morning, then partly sunny with showers likely in the afternoon. Highs 82 to 88 near the shore to around 73 at 4000 feet. Southeast winds up to 10 mph. Chance of rain 60 percent.

Kona

Today: Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 81 to 86 near the shore to around 70 near 5000 feet. Light winds becoming west up to 10 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 69 to 74 near the shore to around 54 near 5000 feet. Northwest winds up to 10 mph in the evening becoming light. Chance of rain 30 percent.

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Tuesday: Mostly sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 82 to 87 near the shore to 68 to 73 near 5000 feet. West winds up to 10 mph. Chance of rain 50 percent.

Waimea

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Today: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 70 to 83. Northeast winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows around 67 near the shore to 55 to 61 near 3000 feet. East winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Tuesday: Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 71 to 84. Northwest winds up to 10 mph shifting to the northeast in the afternoon. Chance of rain 50 percent.

Kohala

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Today: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 70 to 83. Northeast winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows around 67 near the shore to 55 to 61 near 3000 feet. East winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Tuesday: Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 71 to 84. Northwest winds up to 10 mph shifting to the northeast in the afternoon. Chance of rain 50 percent.

South Big Island

Today: Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs around 85 near the shore to around 75 near 5000 feet. East winds up to 15 mph. Chance of rain 40 percent.

Tonight: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows around 68 near the shore to around 52 near 5000 feet. East winds up to 10 mph. Chance of rain 30 percent.

Tuesday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs around 86 near the shore to around 76 near 5000 feet. East winds up to 15 mph shifting to the southeast in the afternoon. Chance of rain 50 percent.

Puna

Today: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 81 to 87 near the shore to around 72 at 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 65 to 72 near the shore to around 54 at 4000 feet. Southeast winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Tuesday: Mostly sunny with isolated showers in the morning, then partly sunny with showers likely in the afternoon. Highs 82 to 88 near the shore to around 73 at 4000 feet. Southeast winds up to 10 mph. Chance of rain 60 percent.

Waikoloa

Today: Sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 82 to 87 near the shore to 68 to 75 above 4000 feet. West winds up to 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows around 73 near the shore to 52 to 59 above 4000 feet. West winds up to 10 mph in the evening becoming light. Chance of rain 30 percent.

Tuesday: Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 83 to 88 near the shore to 69 to 76 above 4000 feet. Northwest winds up to 10 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

A light wind pattern will hold in place today through Wednesday, with showers developing over the island interiors each afternoon, and mainly dry conditions expected each night. More typical trade wind weather will return Thursday through Saturday, with showers favoring windward and mauka areas. The trades could become disrupted again by Sunday, with a sea breezes favoring shower development over the island interiors during the afternoon hours.

Discussion

Currently at the surface, a southwest to northeast oriented trough of low pressure is located around 200 miles north- northeast of Hilo, while a 1029 mb high is centered around 1300 miles north of Honolulu. The trough is moving slowly westward early this morning and has weakened the trade winds to gentle levels. Infrared satellite imagery shows clear to partly cloudy conditions across much of the state, with a few pockets of more extensive cloud cover near the Big Island and over windward sections of Oahu and Kauai. Radar imagery shows scattered showers moving into windward Oahu and Kauai, with very shower activity reaching land over Maui County and the Big Island. Main short term concerns revolve around trade wind trends and rain chances during the next few days.
The trough of low pressure north-northeast of the state will track slowly westward during the next couple days, disrupting the trade wind flow across the island chain. The trades are expected to become disrupted by late morning, with light and variable winds featuring daytime sea breezes and overnight land breezes expected this afternoon through Tuesday. Trade winds should begin to slowly return from east to west across the state on Wednesday as the trough shifts west of the islands and high pressure builds to the distant northeast. Moderate to locally breezy trade winds should then return Thursday through Saturday, with the trades possibly decreasing again by Sunday as the remnants of tropical cyclone Linda disrupt the gradient across the island chain.
As for the remaining weather details, a few trade wind showers should continue to affect Oahu and Kauai this morning. A convective shower regime should take hold this afternoon through Wednesday, featuring the development of scattered showers over interior and mauka locations each afternoon. These showers will then fizzle out in the evening, followed by mainly dry conditions overnight. A more typical trade wind pattern should become re- established Wednesday night through Saturday, with showers favoring windward and mauka areas. A sea breeze driven convective shower pattern will be possible again by Sunday, favoring shower development over the interior of the islands during the afternoon hours.

Aviation

Weakening trade winds will allow local scale land and sea breezes to become more dominant over the islands today. An upper level low drifting into the region from the northeast direction will decrease atmospheric stability allowing cloud heights to deepen. Converging sea breezes will cause clouds to build and showers to develop over each island during the afternoon to early evening hours. Diverging land breezes forming after sunset will cause clouds over island interiors to diminish through the early morning hours.
No AIRMETs in effect and none are expected.

Marine

A surface trough passing north of the state the next few days will disrupt trade flow and ultimately weaken winds around the islands. The western movement of this trough should subtly veer light to gentle breezes east southeast in time through early Wednesday. Reestablishing east trade winds will strengthen by Thursday as the trough moves west of the chain.
South shore surf will be on the rise today with the arrival of an anticipated large, long period south swell. Offshore southern buoys are showing the high period frontrunners while the nearshore PacIOOS Barber’s Point buoy is registering rising swell within the higher energy bands. Several pulses within this swell will have this south shore surf event lasting through mid week. A High Surf Advisory will likely be in effect for south facing shores as early as this afternoon but certainly for peaking surf at or slightly above 10 feet Tuesday and Wednesday.
The ongoing fairly low, moderate period northwest-west swell will be slowly declining through Tuesday. This will have north and west facing shore surf gradually falling through late Tuesday. Surf along east facing shores will remain relatively small the next several days. Swell within the captured fetch from Hurricane Linda in the East Pacific might make it to the east facing shores of the eastern most islands as small, long period east swell by Wednesday.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov

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