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Hawaii County Weather Forecast for September 21, 2022


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Hilo

Today: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs 81 to 87 near the shore to 69 to 75 at 4000 feet. North winds around 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with showers likely. Lows 68 to 75 near the shore to around 57 at 4000 feet. Northeast winds 10 to 15 mph in the evening becoming light. Chance of rain 70 percent.

Thursday: Mostly cloudy. Showers likely in the morning, then scattered showers in the afternoon. Highs 81 to 87 near the shore to 69 to 75 at 4000 feet. East winds around 10 mph. Chance of rain 70 percent.

Kona

Today: Sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 82 to 87 near the shore to around 70 near 5000 feet. Light winds becoming south around 10 mph in the afternoon. Chance of rain 40 percent.

Tonight: Mostly cloudy in the evening then clearing. Isolated showers. Lows 70 to 75 near the shore to around 57 near 5000 feet. Northeast winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

ARTICLE CONTINUES BELOW AD
ARTICLE CONTINUES BELOW AD

Thursday: Sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 83 to 88 near the shore to around 70 near 5000 feet. Southwest winds around 10 mph shifting to the east in the afternoon. Chance of rain 40 percent.

Waimea

Today: Partly sunny. Breezy. Showers likely in the morning, then scattered showers in the afternoon. Highs around 84 near the shore to 75 to 81 near 3000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 69 near the shore to 57 to 64 near 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Thursday: Partly sunny with scattered showers. Highs around 84 near the shore to 75 to 81 near 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Kohala

Today: Partly sunny. Breezy. Showers likely in the morning, then scattered showers in the afternoon. Highs around 84 near the shore to 75 to 81 near 3000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

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Tonight: Mostly cloudy with scattered showers. Lows around 69 near the shore to 57 to 64 near 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Thursday: Partly sunny with scattered showers. Highs around 84 near the shore to 75 to 81 near 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

South Big Island

Today: Breezy. Sunny in the morning, then cloudy with isolated showers in the afternoon. Highs around 86 near the shore to around 74 near 5000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Breezy. Mostly cloudy with isolated showers in the evening, then mostly clear after midnight. Lows around 71 near the shore to around 54 near 5000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Thursday: Breezy. Sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs around 86 near the shore to around 74 near 5000 feet. East winds 10 to 20 mph. Chance of rain 40 percent.

Puna

ARTICLE CONTINUES BELOW AD

Today: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs 81 to 87 near the shore to 69 to 75 at 4000 feet. North winds around 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with showers likely. Lows 68 to 75 near the shore to around 57 at 4000 feet. Northeast winds 10 to 15 mph in the evening becoming light. Chance of rain 70 percent.

Thursday: Mostly cloudy. Showers likely in the morning, then scattered showers in the afternoon. Highs 81 to 87 near the shore to 69 to 75 at 4000 feet. East winds around 10 mph. Chance of rain 70 percent.

Waikoloa

Today: Mostly sunny. Highs 83 to 88 near the shore to 69 to 76 above 4000 feet. Northeast winds 10 to 15 mph.

Tonight: Partly cloudy. Isolated showers in the evening. Lows around 74 near the shore to 53 to 61 above 4000 feet. Northeast winds 10 to 15 mph in the evening becoming light. Chance of rain 20 percent.

Thursday: Sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 83 to 89 near the shore to 70 to 77 above 4000 feet. North winds around 10 mph shifting to the east in the afternoon. Chance of rain 50 percent.

Synopsis

Moderate trade winds will decline through tonight, while continuing to deliver brief showers to windward areas. Winds will ease further and veer out of the east-southeast Thursday and Friday, allowing land and sea breezes to have an effect on island weather. Other than a few windward showers, the land breezes will lead to mostly clear skies during nights and mornings, while afternoon sea breezes will lead to clouds and a few showers over leeward and interior areas. Light to moderate trade winds are expected this weekend, with limited rainfall expected.

Discussion

A stable trade wind flow remains in place this morning, with moderate to locally breezy ENE winds being driven by a surface ridge far to the N, while a ridge aloft is supporting a subsidence inversion near 8000′. With the inversion at this height, incoming cumulus are growing vertically to the point that shower frequency and coverage have increased somewhat overnight, with showers primarily moistening windward areas. As cloud-top heating increases through the morning, shower coverage will follow the typical diurnal trend and diminish.
Trade winds will gradually decline through tonight as a developing cutoff low 900 miles N of Kauai weakens the surface ridge, and pushes it southward. Winds will weaken and veer to the SE, most notably over the western end of the state, as the low tracks SW and gradually weakens, with light to moderate E-SE winds prevailing into the weekend. Long term guidance appears to be trending toward weaker winds into next week as another low passes well N of the area, but confidence is low due to inconsistencies in run-to-run model output.
Even with the diminishing winds and the potential for land breeze development, a few showers are expected to move ashore over windward areas, mainly at night. Meanwhile daytime sea breezes are also expected to produce clouds and a few showers over leeward areas each afternoon. The ridge aloft will be slightly eroded by the low passing to the NW, leading to a brief decrease in stability Thursday night and Friday. While we cannot rule out a briefly heavy shower, mainly in the afternoon, odds favor moderate rainfall through the forecast period.

Aviation

The background trade wind flow is expected to weaken slightly later today and tonight. The atmosphere remains relatively stable, but pockets of increased moisture are moving in from the east. As a result, scattered to broken low clouds with embedded scattered showers are moving into the windward sections of most of the islands early this morning. This is likely producing brief periods of MVFR conditions along some windward facing slopes. Otherwise, VFR conditions will likely prevail across most of the island chain through this morning.
The somewhat lighter background trade wind flow may allow a few more clouds to form across some leeward sections this afternoon. Elsewhere, expect modest cloud cover and trade showers along windward sections from this afternoon into this evening, with only brief periods of MVFR conditions expected.
No AIRMETs are currently in effect, and none are anticipated.

Marine

A surface ridge north of the state will weaken over the next few days as low pressure develops northwest of the area. This will cause winds to become lighter and become more east-southeasterly. The low will move away to the west late Saturday and Sunday with the ridge restrengthening to our north, resulting in returning trade winds.
The current small northwest swell will lower through Thursday. A new long-period south swell will slowly fill in today, peak tonight through early Thursday, then lower late Thursday through Friday. Surf heights may approach low-end advisory levels during the peak of this swell. A slightly smaller south swell is expected over the weekend. Short-period choppy surf along east facing shores will become rather small over the next several days as trade winds diminish over and upwind of the state.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov



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