Weather Forecast

Hawaii County Weather Forecast for April 20, 2023

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Photo Credit: James Grenz

Hilo

Today: Mostly cloudy. Scattered showers in the morning, then numerous showers and slight chance of thunderstorms in the afternoon. Highs around 83 near the shore to around 67 at 4000 feet. Southeast winds up to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 68 near the shore to around 54 at 4000 feet. South winds up to 10 mph. Chance of rain 50 percent.

Friday: Partly sunny with scattered showers. Highs around 83 near the shore to around 67 at 4000 feet. Southeast winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 50 percent.

Kona

Today: Mostly sunny early in the morning then becoming partly sunny. Scattered showers in the morning, then scattered showers and slight chance of thunderstorms in the afternoon. Highs around 85 near the shore to around 70 near 5000 feet. Southwest winds up to 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 68 to 74 near the shore to around 54 near 5000 feet. Southwest winds up to 10 mph in the evening becoming light. Chance of rain 40 percent.

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Friday: Sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs around 85 near the shore to around 70 near 5000 feet. Northwest winds up to 10 mph. Chance of rain 50 percent.

Waimea

Today: Mostly sunny early in the morning then becoming partly sunny. Scattered showers in the morning, then scattered showers and slight chance of thunderstorms in the afternoon. Highs around 82 near the shore to 71 to 77 near 3000 feet. Light winds. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 67 near the shore to 52 to 61 near 3000 feet. Light winds. Chance of rain 50 percent.

Friday: Partly sunny with scattered showers. Highs around 82 near the shore to 71 to 77 near 3000 feet. North winds up to 15 mph shifting to the east in the afternoon. Chance of rain 50 percent.

Kohala

Today: Mostly sunny early in the morning then becoming partly sunny. Scattered showers in the morning, then scattered showers and slight chance of thunderstorms in the afternoon. Highs around 82 near the shore to 71 to 77 near 3000 feet. Light winds. Chance of rain 50 percent.

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Tonight: Mostly cloudy with scattered showers. Lows around 67 near the shore to 52 to 61 near 3000 feet. Light winds. Chance of rain 50 percent.

Friday: Partly sunny with scattered showers. Highs around 82 near the shore to 71 to 77 near 3000 feet. North winds up to 15 mph shifting to the east in the afternoon. Chance of rain 50 percent.

South Big Island

Today: Partly sunny. Scattered showers in the morning, then scattered showers and slight chance of thunderstorms in the afternoon. Highs around 85 near the shore to around 71 near 5000 feet. South winds up to 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows around 69 near the shore to around 54 near 5000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Friday: Mostly sunny. Breezy. Isolated showers in the afternoon. Highs around 85 near the shore to around 71 near 5000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Puna

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Today: Mostly cloudy. Scattered showers in the morning, then numerous showers and slight chance of thunderstorms in the afternoon. Highs around 83 near the shore to around 67 at 4000 feet. Southeast winds up to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 68 near the shore to around 54 at 4000 feet. South winds up to 10 mph. Chance of rain 50 percent.

Friday: Partly sunny with scattered showers. Highs around 83 near the shore to around 67 at 4000 feet. Southeast winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 50 percent.

Waikoloa

Today: Mostly sunny early in the morning then becoming partly sunny. Scattered showers in the morning, then scattered showers and slight chance of thunderstorms in the afternoon. Highs around 85 near the shore to 66 to 73 above 4000 feet. Northwest winds up to 10 mph. Chance of rain 50 percent.

Tonight: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 69 to 74 near the shore to 49 to 57 above 4000 feet. Light winds. Chance of rain 50 percent.

Friday: Mostly sunny. Isolated showers in the afternoon. Highs around 85 near the shore to 66 to 73 above 4000 feet. Northwest winds up to 10 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A stationary front in the vicinity of the Big Island, will weaken into a trough and drift back westward across the central smaller islands tonight. This pattern will maintain some showers across the islands through Friday. Trade winds will return Friday across most of the state, before weakening and veering southeast this weekend. Conditions will be mainly stable for the weekend, with mostly fair weather expected with some scattered showers.

Discussion

Current radar shows showers continue to drift across the islands this morning. Radar estimates show mainly light rainfall occurring this morning, however some isolated enhanced rainfall remained embedded within the showers.
Today through tonight…showers will continue across the islands as the weakened boundary, and band of enhanced moisture (PW 1.60″ to 1.70″), begin to drift back westward across the state. The boundary is forecast to finally weaken north of the region Friday. Light background winds today will also promote afternoon sea breeze showers for island interiors and mountain areas. With the lighter winds, showers will likely be slow moving and capable of producing brief downpours. Models also indicate weak instability (SW 0C to -1C) across the Big Island today, suggesting some chance for isolated thunderstorms remaining possible along the Big Island slopes. Later tonight, a ridge of high pressure will begin to restrengthen north of the state. This pattern should begin to establish trade wind flow over the state.
Friday into the weekend…an area of high pressure well northeast of the state, will maintain moderate southeast trades over the region into the first half of the weekend. However a cold front associated with low pressure well northwest of the state, will approach Kauai and weaken the trade wind flow during the second half of the weekend. With the southeast background wind flow, lighter winds are expected over Oahu and Kauai due to shadowing from the Big Island, allowing for afternoon sea breezes and potential showers for leeward areas. For Maui County and the Big Island, light to moderate east to southeast winds will generate some trade wind showers, mainly at night through early morning. Late in the weekend, shower chances may increase across Kauai as the front approaches from the northwest.
Monday through next week…models are in fairly similar agreement with the approaching front from the northwest, moving eastward and potentially increasing rainfall chances to begin the work week. Then the boundary weakens and drifts quickly east away from the state, helping to establish mainly stable and drier conditions (PW under 1.30″) and limiting the areal coverage of showers by mid week.

Aviation

Expect mostly VFR conditions for all airfields today as drier air continues to move in from the west. Light winds today will produce stable sea breezes over each island during the day with land breezes overnight. A few showers are possible mainly over island interior sections during the day.
No AIRMETs in effect and none are expected.

Marine

Winds will remain light and variable across the vast majority of the marine area today, as a weak stationary front in the vicinity of the Big Island weakens into a trough. The trough will shift west tonight and Friday as a ridge of high pressure builds north of the islands, allowing light to moderate trades to return. An approaching front will ease the winds over the western islands Friday night through the weekend. Moderate trades will hold over the eastern end of the state through Saturday before becoming light and variable on Sunday. A weakening front will push southward into the islands early next week, bringing a return of light to moderate trade winds.
The current moderate sized (short to medium period) west- northwest swell will peak today, then gradually decline through Saturday. A new long-period northwest swell is forecast to arrive Friday night, build through the day Saturday, then peak Saturday night into Sunday. A reinforcing long period northwest swell will move in Sunday night, peak on Monday, then slowly lower through the middle of next week.
Surf along south facing shores will remain tiny through Friday. A new long-period south swell will arrive Friday night, peak over the weekend, and then slowly decline through the middle of next week. This swell will give south shore surf a noticeable boost to near the summertime average Saturday through Monday.
Surf along east facing shores will remain small through the middle of next week.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov

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