Weather Forecast

Hawaii County Weather Forecast for April 22, 2021

April 22, 2021, 7:16 AM HST
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Photo Credit: James Grenz

Hilo

Today: Scattered showers, mainly before 1pm. Mostly cloudy, with a high near 82. Light and variable wind becoming east northeast 6 to 11 mph in the afternoon. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Showers likely, mainly after 1am. Cloudy, with a low around 63. Light and variable wind becoming west 5 to 7 mph in the evening. Chance of precipitation is 70%. New precipitation amounts of less than a tenth of an inch possible.

Friday: Showers likely, with thunderstorms also possible after 1pm. Cloudy, with a high near 82. West wind around 9 mph becoming northeast in the morning. Chance of precipitation is 70%. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

Kona

Today: Isolated showers after noon. Partly sunny, with a high near 83. Calm wind becoming southwest 5 to 9 mph. Chance of precipitation is 20%.

Tonight: Isolated showers before midnight. Mostly cloudy, with a low around 63. Calm wind becoming east southeast around 6 mph after midnight. Chance of precipitation is 20%.

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Friday: Scattered showers and thunderstorms after noon. Partly sunny, with a high near 84. West southwest wind 5 to 10 mph becoming light and variable in the afternoon. Chance of precipitation is 30%. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

Waimea

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Today: Scattered showers, mainly before 1pm. Partly sunny, with a high near 74. Windy, with a northeast wind 16 to 25 mph, with gusts as high as 36 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers, mainly after 7pm. Mostly cloudy, with a low around 52. Breezy, with a northeast wind 17 to 20 mph, with gusts as high as 28 mph. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Friday: Scattered showers, with thunderstorms also possible after 1pm. Mostly cloudy, with a high near 76. Windy, with a northeast wind 17 to 24 mph, with gusts as high as 34 mph. Chance of precipitation is 40%. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

Kohala

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Today: Scattered showers, mainly before noon. Mostly cloudy, with a high near 67. Windy, with an east wind 17 to 26 mph, with gusts as high as 39 mph. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Showers likely, mainly after midnight. Cloudy, with a low around 44. Breezy, with an east wind 18 to 21 mph, with gusts as high as 39 mph. Chance of precipitation is 70%. New precipitation amounts of less than a tenth of an inch possible.

Friday: Showers likely, with thunderstorms also possible after noon. Cloudy, with a high near 69. Windy, with an east wind 21 to 24 mph, with gusts as high as 34 mph. Chance of precipitation is 70%. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

South Big Island

Today: Mostly sunny, with a high near 83. Windy, with an east wind 17 to 25 mph, with gusts as high as 30 mph.

Tonight: Partly cloudy, with a low around 69. Windy, with an east northeast wind 21 to 24 mph, with gusts as high as 31 mph.

Friday: Mostly sunny, with a high near 83. Windy, with an east wind 21 to 26 mph, with gusts as high as 34 mph.

Puna

Today: Scattered showers. Cloudy, with a high near 79. Breezy, with a north northwest wind 5 to 15 mph becoming east northeast in the morning. Winds could gust as high as 21 mph. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Showers likely, mainly after midnight. Cloudy, with a low around 61. Northeast wind 6 to 10 mph becoming northwest in the evening. Chance of precipitation is 70%. New precipitation amounts of less than a tenth of an inch possible.

Friday: Showers likely, with thunderstorms also possible after noon. Cloudy, with a high near 79. Northwest wind 7 to 11 mph becoming northeast in the morning. Chance of precipitation is 70%. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

Waikoloa

Today: Mostly sunny, with a high near 80. Windy, with a southeast wind 11 to 16 mph becoming east northeast 18 to 23 mph in the morning. Winds could gust as high as 33 mph.

Tonight: Mostly clear, with a low around 62. Breezy, with an east wind 14 to 18 mph, with gusts as high as 25 mph.

Friday: Mostly sunny, with a high near 82. Windy, with an east northeast wind 14 to 24 mph, with gusts as high as 34 mph.

Detailed Forecast

Synopsis

Moderate to breezy easterly trade winds will return today and persist through the weekend, with clouds and showers favoring windward and mountain locations. Windward shower coverage could increase late Friday through Saturday night as an upper disturbance moves through from north to south. Warm and humid conditions may return early next week as the trade winds diminish in response to a cold front passing far to the north.

Discussion

The surface trough analyzed near Kauai that disrupted the trade winds through the first half of the week will begin to retreat westward and away from the area through Friday. A pattern transition will result locally with easterly trade winds returning from east to west as high pressure builds to the north. This combined with rising upper heights and plenty of mid-level dry air will translate to more of a stable trade wind regime through tonight. Showers will favor the typical windward and mountain locations – with the best coverage likely through the overnight and early morning periods.
Windward shower coverage may increase late Friday through Saturday night as an upper low drops southward into the area. Some showers could spill over into leeward locations as the inversion lifts/weakens and the trades become breezy. In addition to the increasing shower coverage, a thunderstorm or two can’t be ruled out over the Big Island slopes through the afternoon hours Friday and Saturday.
Guidance remains in decent agreement early next week and shows the previously discussed upper low briefly drifting south of the state Sunday through Sunday night, then lifting back through the area and phasing with a shortwave trough passing far to the north Monday through Tuesday. Subtropical ridge will weaken once again as the attendant cold front passes to the north. If this scenario evolves, a land and sea breeze regime with warm and humid conditions will return and continue through the first half of next week. Clouds and showers will shift back over interior and leeward locations through the afternoon hours.

Aviation

Light trade winds appear to be returning near Maui and the Big Island early this morning. The background flow remains light and variable in the vicinity of the smaller islands west of Maui. Local land breezes are dominating the low-level flow over most of the individual islands. The land breezes have kept low clouds to a minimum over most areas. However, scattered to broken low clouds and isolated showers are moving into the windward side of the Big Island. This may cause brief MVFR conditions along the Big Island windward slopes this morning. Otherwise, VFR conditions are expected to prevail over most areas this morning.
Light to moderate trade winds are forecast to return across the entire state later today. The low-level trade wind flow may bring some low clouds and brief showers to the windward sections on some of the islands later today and tonight.
No AIRMETS are currently in effect, and none are anticipated through this afternoon.

Marine

A surface high passing north of the islands today through Friday then stalling north-northeast over the weekend will result in a boost in the trade winds with speeds reaching locally strong for waters around Maui County and south of the Big Island between today and Sunday. The trades are then expected to trend down while becoming southeast Monday, then hold through Wednesday as the high weakens.
The arrival of the northwest has resulted in a small to moderate bump along the north and west facing shores. This swell is slated to peak today followed by slow decline through Friday. Expect a small to moderate, long- period west- northwest swell to arrive next Monday night and peak Tuesday, followed by a slow decline. A small short period west- northwest to northwest pulse is expected reach our north and west facing shores next week Wednesday night.
A continuous stream of small, but long-period swell from the south and southwest will maintain small surf along south facing shores through next week Wednesday. Surf along the east facing shores will be on the rise Friday and Saturday when the trades turn breezy. Expect surf to build to small to moderate heights, then start diminishing Monday as the trade winds weaken.

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.

Data Courtesy of NOAA.gov

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