Weather Forecast

Hawaii County Weather Forecast for August 18, 2021

August 18, 2021, 7:16 AM HST
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Photo Credit: James Grenz

Hilo

Today: Partly sunny with scattered showers. Highs 81 to 87 near the shore to around 72 at 4000 feet. Southeast winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with numerous showers. Lows 66 to 73 near the shore to around 55 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 70 percent.

Thursday: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs 81 to 87 near the shore to around 72 at 4000 feet. Northeast winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 70 percent.

Kona

Today: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 82 to 87 near the shore to around 71 near 5000 feet. Light winds becoming west up to 10 mph in the afternoon. Chance of rain 40 percent.

Tonight: Partly cloudy with isolated showers. Lows 70 to 75 near the shore to around 55 near 5000 feet. Light winds. Chance of rain 20 percent.

ARTICLE CONTINUES BELOW AD

Thursday: Sunny. Isolated showers in the afternoon. Highs 82 to 87 near the shore to around 72 near 5000 feet. Northeast winds up to 10 mph shifting to the west in the afternoon. Chance of rain 20 percent.

Waimea

ARTICLE CONTINUES BELOW AD

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

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 68 near the shore to 56 to 62 near 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Thursday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 70 to 83. East winds 10 to 25 mph. Chance of rain 50 percent.

Kohala

ARTICLE CONTINUES BELOW AD

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

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 68 near the shore to 56 to 62 near 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Thursday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 70 to 83. East winds 10 to 25 mph. Chance of rain 50 percent.

South Big Island

Today: Mostly sunny. Breezy. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 85 near the shore to around 75 near 5000 feet. East winds up to 20 mph. Chance of rain 40 percent.

Tonight: Partly cloudy. Breezy. Isolated showers in the evening. Lows around 69 near the shore to around 53 near 5000 feet. Northeast winds up to 20 mph. Chance of rain 20 percent.

Thursday: Sunny and breezy. Highs around 85 near the shore to around 75 near 5000 feet. East winds 10 to 25 mph.

Puna

Today: Partly sunny with scattered showers. Highs 81 to 87 near the shore to around 72 at 4000 feet. Southeast winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with numerous showers. Lows 66 to 73 near the shore to around 55 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 70 percent.

Thursday: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs 81 to 87 near the shore to around 72 at 4000 feet. Northeast winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 70 percent.

Waikoloa

Today: Mostly sunny with isolated showers 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. Light winds becoming northwest up to 10 mph in the afternoon. Chance of rain 40 percent.

Tonight: Partly cloudy with isolated showers. Lows around 74 near the shore to 53 to 60 above 4000 feet. Light winds becoming southeast up to 15 mph after midnight. Chance of rain 20 percent.

Thursday: Sunny and breezy. Highs 83 to 88 near the shore to 69 to 76 above 4000 feet. East winds up to 20 mph shifting to the north in the afternoon.

Detailed Forecast

Synopsis

Sea breezes will continue today with scattered showers in the afternoon to early evening forecast. Expect a return back to passing windward and mountain showers in moderate to locally breezy trade winds starting tonight into Saturday. A tropical low will pass just north of the islands from late Saturday into Monday disrupting the trade wind flow once again. Expect humid sea breeze conditions during the day and the potential for locally heavy showers during this time period.

Discussion

An upper level low passing north of the state will drift northwestward away from the islands through Thursday. More stable weather trends are expected as this unstable low drifts away from the state. Expect converging sea breeze winds again today with building trades by tonight. Periods of afternoon showers will develop mainly along these convergence zones favoring western and interior sections of each island.
Thursday through Saturday…The high pressure ridge will build in far north of the state, increasing trade winds into the moderate range through Saturday. Increasing atmospheric stability will also decrease shower activity with brief passing showers favoring more typical windward and mountain areas.
Sunday and Monday…A tropical low, the remnants of Tropical Cyclone Linda, will pass just north of the Hawaiian Islands shutting down the trade winds once again. Deeper tropical moisture will move up into the islands producing very humid conditions. In the absence of trade winds, local scale land and sea breezes will develop, and converging sea breeze winds will produce periods of showers over island interior sections. Some of these showers may become locally heavy at times. Due to the uncertainties of this long range pattern it remains too early for island by island weather impacts. Stay tuned for more detailed information, as the time period grows shorter, and this extended range forecast evolves.

Aviation

Trade flow will gradually return over the next few days, shifting our cloud and shower pattern to one favoring windward areas. Expect VFR conditions across the TAF sites even as low clouds stubbornly cling to portions of Oahu this morning. An area of low clouds may reach windward and southeast portions of the Big Island within the next few hours, possibly spreading MVFR ceilings there.
No AIRMETs are currently in effect.

Marine

A surface trough extending south to just east of Kauai will continue to move west of the island later today. Trade winds will be returning to the area later today through tonight with trades reaching locally strong on Thursday. This will not last long as trades are expected to turn light and variable over the weekend. This comes about as the remnants of tropical cyclone Linda passes north of the islands Sunday through Monday night.
A above normal south swell may have peaked as per deep ocean buoys 51002 and 51003 south of the islands. So the surf will be trending down gradually through the day today. A high surf advisory (HSA) is in effect for the south facing shores through this afternoon, with the likelihood that it will be extended later today. No significant swells from the south are through early next week, although small moderate period swells will prevent the surf from going flat.
A small northwest pulse will continue to trend down today as well, with no significant northerly swells expected through the period. The swell from Hurricane Linda is expected to arrive this afternoon and spread west through Thursday and maintain moderate surf along east facing shores into the weekend.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 PM HST this evening for south facing shores of all islands.

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Data Courtesy of NOAA.gov

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