Weather Forecast

Hawaii County Weather Forecast for September 24, 2021

September 24, 2021, 7:16 AM HST
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Hilo

Today: Sunny early in the morning, then partly sunny with a 20 percent chance of showers in the late morning and afternoon. Highs 80 to 86 near the shore to 68 to 73 at 4000 feet. Northeast winds up to 15 mph.

Tonight: Mostly cloudy with showers likely. Lows around 68 near the shore to around 54 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 60 percent.

Saturday: Mostly cloudy. Showers likely in the morning, then scattered showers in the afternoon. Highs 80 to 86 near the shore to 68 to 73 at 4000 feet. East winds up to 15 mph. Chance of rain 60 percent.

Kona

Today: Sunny early in the morning, then partly sunny with a 20 percent chance of showers in the late morning and afternoon. Highs around 86 near the shore to around 73 near 5000 feet. Light winds.

Tonight: Partly cloudy. Lows 68 to 74 near the shore to around 54 near 5000 feet. Light winds.

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Saturday: Mostly sunny in the morning, then mostly cloudy with isolated showers in the afternoon. Highs around 86 near the shore to around 73 near 5000 feet. Light winds becoming west up to 10 mph in the afternoon. Chance of rain 20 percent.

Waimea

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Today: Mostly sunny. Breezy. A 20 percent chance of showers in the late morning and afternoon. Highs around 82 near the shore to 73 to 80 near 3000 feet. East winds up to 20 mph.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 67 near the shore to 54 to 61 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Saturday: Breezy. Mostly cloudy with scattered showers. Highs around 82 near the shore to 73 to 80 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Kohala

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Today: Mostly sunny. Breezy. A 20 percent chance of showers in the late morning and afternoon. Highs around 82 near the shore to 73 to 80 near 3000 feet. East winds up to 20 mph.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 67 near the shore to 54 to 61 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Saturday: Breezy. Mostly cloudy with scattered showers. Highs around 82 near the shore to 73 to 80 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

South Big Island

Today: Breezy. Sunny early in the morning, then partly sunny with a 20 percent chance of showers in the late morning and afternoon. Highs around 85 near the shore to around 74 near 5000 feet. East winds up to 25 mph.

Tonight: Partly cloudy. Breezy. Lows around 68 near the shore to around 53 near 5000 feet. East winds 10 to 20 mph.

Saturday: Breezy. Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 85 near the shore to around 74 near 5000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Puna

Today: Sunny early in the morning, then partly sunny with a 20 percent chance of showers in the late morning and afternoon. Highs 80 to 86 near the shore to 68 to 73 at 4000 feet. Northeast winds up to 15 mph.

Tonight: Mostly cloudy with showers likely. Lows around 68 near the shore to around 54 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 60 percent.

Saturday: Mostly cloudy. Showers likely in the morning, then scattered showers in the afternoon. Highs 80 to 86 near the shore to 68 to 73 at 4000 feet. East winds up to 15 mph. Chance of rain 60 percent.

Waikoloa

Today: Mostly sunny. Breezy. Highs around 85 near the shore to 69 to 75 above 4000 feet. Northeast winds up to 20 mph.

Tonight: Partly cloudy. Lows 69 to 74 near the shore to 50 to 57 above 4000 feet. East winds up to 10 mph.

Saturday: Mostly sunny in the morning then becoming partly sunny. Highs around 85 near the shore to 69 to 75 above 4000 feet. North winds up to 10 mph.

Detailed Forecast

Synopsis

A trade wind pattern will bring passing clouds and showers to mainly windward and mountain areas through the weekend and into next week, thanks to persistent ridging to our north. A weak surface trough passing westward to the south of the islands will boost rainfall across windward Big Island late Saturday and Sunday.

Discussion

A high far northeast of the state keeps a trade wind weather pattern across the forecast area this morning. A timely ASCAT pass showed that winds increased in strength slightly overnight, enough to issue a Small Craft Advisory for typically windy waters around Maui and the Big Island. Overnight soundings show an inversion base near 5500 feet, significantly lower than the previous afternoon, which keeps convective buildups and rainfall limited. Satellite and radar show low clouds and showers favoring windward areas. A few low clouds cling to lower Kona slopes on the Big Island as well.
Expect a trade wind weather pattern across the area through the forecast period. Ridging aloft will maintain a stable airmass as clouds and showers favor windward areas. A trough far southeast of the state is expected to swing northwestward over the next few days and skirt the Big Island, likely increasing clouds and showers there as early as late Saturday and into early Sunday. Trade winds will receive a boost in strength as the trough passes by to our south.

Aviation

A high is now centered far northeast of the islands and is remaining nearly stationary. Thus, trade winds will continue to be in the moderate to locally breezy range through today and beyond. Showers moving along on the trades will bring MVFR in lower ceilings and visibilities to mainly windward and mauka sections from time to time. VFR conditions will prevail otherwise.
No AIRMETs are currently in effect.

Marine

Surface high pressure northwest to north of the islands that is building in behind a weak Central Pacific cold front will produce a tight enough pressure gradient down across the state in continued support of generally fresh to locally strong trade winds. Early morning ASCAT satellite passes have warranted the issuance of a Small Craft Advisory (SCA) for the typically windier channels and bays around Maui County and waters south of Big Island through Saturday afternoon. An extension in time will likely be required for this SCA. A surface trough passing south of the area this weekend, along with this tighter north pressure gradient across the islands, will provide a subtle boost to weekend trades. An incoming northwest swell has elevated sea heights to near 11 feet in the northwest offshore waters. These elevated seas will move into more western nearshore waters through Saturday.
Long period energy from an incoming north northwest swell has reached the northwest offshore buoys, as well as the nearshore buoy off of Hanalei, Kauai. This new swell will build surf to as high as double overhead over the more northwest-exposed reefs and coastlines through Saturday. North and west facing shore surf should peak below High Surf Advisory thresholds later today and Saturday. This first northwest swell of the young autumn season will begin to diminish late Saturday into Sunday. The next mentionable smaller west northwest swell will come from Tropical Cyclone Mindulle in the West Pacific and arrive next weekend. South facing shore surf will hold at recent levels the next several days as small, background southwest south swell energy hangs on through the majority of next week. Short period wind waves generated from fresh trade winds will support mainly small, choppy surf along many east facing shores.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Saturday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov

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