Weather Forecast

Hawaii County Weather Forecast for July 21, 2023

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Hilo

Today: Mostly cloudy. Light showers likely in the morning, then scattered light showers in the afternoon. Highs 80 to 87 near the shore to 66 to 72 at 4000 feet. East winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Scattered light showers in the evening, then light showers likely after midnight. Lows 64 to 73 near the shore to around 58 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 70 percent.

Saturday: Partly sunny with scattered showers. Highs 81 to 87 near the shore to 66 to 72 at 4000 feet. North winds around 10 mph shifting to the east in the afternoon. Chance of rain 50 percent.

Kona

Today: Mostly sunny in the morning then becoming mostly cloudy. Isolated light showers. Highs 84 to 89 near the shore to around 72 near 5000 feet. West winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy in the evening then becoming mostly clear. Isolated light showers. Lows around 74 near the shore to 52 to 58 near 5000 feet. Northwest winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

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Saturday: Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 84 to 90 near the shore to around 72 near 5000 feet. Northeast winds around 10 mph shifting to the west up to 10 mph in the afternoon. Chance of rain 40 percent.

Waimea

Today: Partly sunny. Breezy. Scattered light showers in the morning, then isolated light showers in the afternoon. Highs around 81 near the shore to 70 to 80 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Breezy. Isolated light showers in the evening, then scattered light showers after midnight. Lows 65 to 73 near the shore to 57 to 64 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Saturday: Breezy. Partly sunny with scattered showers. Highs around 82 near the shore to 71 to 81 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Kohala

Today: Partly sunny. Breezy. Scattered light showers in the morning, then isolated light showers in the afternoon. Highs around 81 near the shore to 70 to 80 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

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Tonight: Mostly cloudy. Breezy. Isolated light showers in the evening, then scattered light showers after midnight. Lows 65 to 73 near the shore to 57 to 64 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Saturday: Breezy. Partly sunny with scattered showers. Highs around 82 near the shore to 71 to 81 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

South Big Island

Today: Mostly sunny in the morning then becoming mostly cloudy. Breezy. Highs around 86 near the shore to around 69 near 5000 feet. East winds 10 to 20 mph.

Tonight: Mostly cloudy in the evening then clearing. Breezy. Lows around 75 near the shore to around 55 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 87 near the shore to around 69 near 5000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Puna

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Today: Mostly cloudy. Light showers likely in the morning, then scattered light showers in the afternoon. Highs 80 to 87 near the shore to 66 to 72 at 4000 feet. East winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Scattered light showers in the evening, then light showers likely after midnight. Lows 64 to 73 near the shore to around 58 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 70 percent.

Saturday: Partly sunny with scattered showers. Highs 81 to 87 near the shore to 66 to 72 at 4000 feet. North winds around 10 mph shifting to the east in the afternoon. Chance of rain 50 percent.

Waikoloa

Today: Mostly sunny in the morning then becoming partly sunny. Highs 85 to 91 near the shore to 67 to 75 above 4000 feet. North winds 10 to 15 mph.

Tonight: Partly cloudy. Lows around 75 near the shore to around 55 above 4000 feet. North winds around 10 mph shifting to the east after midnight. Gusts up to 30 mph.

Saturday: Sunny in the morning then becoming partly sunny. Highs 86 to 91 near the shore to 68 to 75 above 4000 feet. East winds 10 to 15 mph shifting to the north in the afternoon.

Detailed Forecast

Synopsis

Breezy trade winds will continue into next week, with low clouds and brief showers favoring windward and mauka areas, especially night and morning.

Discussion

Slow-moving surface high pressure to the distant N of the islands will support breezy trade winds through the next week, with subtle day-to-day fluctuations. A nearby mid-level ridge will support a strong and relatively low subsidence inversion (currently based near 5000 feet) that will limit rainfall coverage and amounts, with brief showers over windward areas favoring nights and mornings. A persistent and seasonable trough aloft to the N of the islands will bring periods of thin high clouds through the next week.
The Big Island's leeward slopes will see afternoon and evening clouds that will drop a few showers before gradually dissipating overnight. Even with the strong stability in place, a few spots (Kealakekua and Waiaha) received close to an inch of rain in the 12 hour period ending at 2 am this morning.
Current satellite images show broken to overcast low clouds streaming over the islands from the E, with radar detecting randomly distributed light showers. Some diurnal decrease in cloud cover is expected by this afternoon, only to increase again overnight. An area of increased PWAT currently near 140W may arrive late Saturday into Sunday, bringing the potential for an increase in windward shower coverage.

Aviation

Breezy trade winds will continue through the 24-hr forecast and beyond, with clouds and light showers favoring windward and mountain areas. The broken stratus/stratocumulus deck will lead to periods of MVFR CIGS through the morning hours across windward areas, especially in and around any light showers that move through.
AIRMET Tango remains in effect for tempo moderate turbulence below 9000 feet over and immediately south through west of mountains on all islands.
AIRMET Sierra is now in effect for mountain obscuration over windward areas/slopes, which will likely persist through the morning hours.

Marine

Surface high pressure far northwest of the state will slowly move east southeast the next few days. The pressure gradient south of the weakening high will remain tight enough to maintain generally fresh to locally strong trade winds across our nearshore waters through next week. This morning's ASCAT pass across the eastern third of the island chain observed a wide swath of Small Craft Advisory (SCA) level winds through the notoriously windier Alenuihaha Channel and around Big Island's South Point. Areawide trades are forecast to slightly back off the next couple of days as the center of the high moves closer to the state but still stay up around Maui County and Big Island's coastal waters into next week.
No significant arriving swell from any direction the next several days will equate to small surf across all shores into early next week. Choppy surf primarily driven by trade wind energy along east- facing shores will remain relatively small. Very small, long period south southwest (200 degree) swell will move around the islands from Sunday through Tuesday. This background energy will provide a small bump to the south-facing shore surf heights.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM 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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