Weather Forecast

Hawaii County Weather Forecast for April 19, 2021

April 19, 2021, 7:16 AM HST
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Photo Credit: James Grenz

Hilo

Today: Scattered showers, mainly before 1pm. Partly sunny, with a high near 83. Southwest wind 8 to 10 mph becoming east southeast in the afternoon. 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 64. South southwest wind 6 to 9 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Tuesday: Scattered showers, mainly before 1pm. Partly sunny, with a high near 83. South southwest wind 6 to 11 mph becoming east southeast in the afternoon. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Kona

Today: Isolated showers after 1pm. Partly sunny, with a high near 83. Calm wind becoming west 5 to 8 mph in the afternoon. Chance of precipitation is 20%.

Tonight: Isolated showers. Mostly cloudy, with a low around 64. West northwest wind around 5 mph becoming calm in the evening. Chance of precipitation is 20%.

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Tuesday: Isolated showers before 7am, then isolated showers after 1pm. Partly sunny, with a high near 83. Light and variable wind becoming west northwest 5 to 9 mph in the morning. Chance of precipitation is 20%.

Waimea

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Today: Isolated showers after noon. Partly sunny, with a high near 74. Light and variable wind becoming west around 6 mph in the afternoon. Chance of precipitation is 20%.

Tonight: Isolated showers before midnight. Mostly cloudy, with a low around 53. West wind around 6 mph becoming calm in the evening. Chance of precipitation is 20%.

Tuesday: Scattered showers after noon. Partly sunny, with a high near 74. Calm wind becoming west around 6 mph in the morning. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Kohala

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Today: Scattered showers after noon. Partly sunny, with a high near 67. West southwest wind around 6 mph becoming calm in the afternoon. Chance of precipitation is 30%.

Tonight: Isolated showers before midnight. Partly cloudy, with a low around 45. Calm wind. Chance of precipitation is 20%.

Tuesday: Isolated showers after noon. Mostly cloudy, with a high near 67. Light and variable wind becoming east northeast 5 to 10 mph in the afternoon. Chance of precipitation is 20%.

South Big Island

Today: Isolated showers. Partly sunny, with a high near 83. Breezy, with an east wind 20 to 22 mph, with gusts as high as 29 mph. Chance of precipitation is 20%.

Tonight: Isolated showers. Partly cloudy, with a low around 70. Breezy, with an east northeast wind 17 to 21 mph, with gusts as high as 26 mph. Chance of precipitation is 20%.

Tuesday: Isolated showers. Partly sunny, with a high near 83. Breezy, with an east wind 13 to 21 mph, with gusts as high as 25 mph. Chance of precipitation is 20%.

Puna

Today: Scattered showers, mainly before noon. Partly sunny, with a high near 81. South southwest wind 6 to 11 mph becoming southeast in the morning. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers. Mostly cloudy, with a low around 62. Southeast wind 5 to 9 mph becoming light south southwest. Chance of precipitation is 30%. New precipitation amounts between a tenth and quarter of an inch possible.

Tuesday: Scattered showers, mainly before noon. Partly sunny, with a high near 81. South wind 5 to 11 mph becoming east northeast in the afternoon. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Waikoloa

Today: Isolated showers after noon. Mostly sunny, with a high near 80. Light and variable wind becoming west northwest 5 to 10 mph in the afternoon. Chance of precipitation is 20%.

Tonight: Isolated showers. Partly cloudy, with a low around 63. West wind 5 to 7 mph becoming calm in the evening. Chance of precipitation is 20%.

Tuesday: Isolated showers after noon. Partly sunny, with a high near 80. Light and variable wind becoming west northwest 5 to 10 mph. Chance of precipitation is 20%.

Detailed Forecast

Synopsis

An approaching front will disrupt the trade winds across much of the state today through Wednesday, resulting in a land and sea breeze pattern across the island chain. This light wind regime will focus showers over interior locations during the day and locations near the coast at night. Shower activity will remain limited today, with an increase in showers expected tonight and Tuesday over Oahu and Kauai as an upper level disturbance moves through. A thunderstorm or two is also not out of the question over the Garden Isle. Moderate to breezy trades and more typical trade wind weather will return Thursday and continue through next weekend, with showers favoring windward and mauka locales.

Discussion

Currently at the surface, a 1030 mb high is centered around 1650 miles northeast of Honolulu, while a cold front is located around 750 miles northwest of Kauai. Light winds have developed over the western islands, with land breezes present in most areas, while light to moderate east-southeasterly boundary layer flow now established over the eastern end of the state. Infrared satellite imagery shows mostly clear to partly cloudy conditions in most areas. Radar imagery shows a few showers moving into east and southeast facing slopes and coasts of most islands, although most of the shower activity remains offshore. Main short term concern revolves around the potential for some unsettled weather Monday night through Wednesday.
A cold front approaching from the northwest and a building high to the far northeast, will keep southeasterly boundary layer flow in place through mid week. The Big Island terrain will block the stronger winds from reaching the smaller islands, allowing for widespread land and sea breeze development today through Wednesday. A new surface ridge is forecast to build to the north of the islands during the second half of the work week, bringing a return of moderate trade winds by Thursday, with the trades then ramping up to breezy levels Friday through the weekend.
As for the remaining weather details, the land breeze and sea breeze pattern expected through mid week, will favor showers developing over interior locations during the day and areas near the coast at night. Models continue to advertise an increase in deep layer moisture lifting up from the south and over the western islands late Monday night through Wednesday. This will likely increase shower coverage over Kauai and Oahu during this time, with some locally heavy rainfall and even a thunderstorm or two possible over Kauai late Monday night and Tuesday as an upper level disturbance moves overhead. A more typical trade wind pattern will return Wednesday night and linger through the weekend, with showers favoring windward and mauka areas.

Aviation

A cold front approaching the islands from the northwest will weaken the ridge north of the islands, causing trade winds to transition to a light and variable wind pattern for most areas. These light large scale winds will allow local scale land and sea breezes to develop over each island. Converging sea breeze winds during the daylight hours will build clouds over island mountain and interior sections. A few showers may develop over these areas in the late afternoon to early evening time periods.
Mostly VFR conditions are forecast with the possibility for Tempo BKN025 along the east to southeast slopes of the Big Island, and over island interior sections in the afternoon to early evening.
No AIRMETs in effect and none are expected.

Marine

Winds have shifted out of the southeast overnight due to an approaching front an upper trough from the northwest. This shift will translate to a land and sea breeze regime along the coasts for most areas through the first half of the week. The exception will be over the windward waters of the Big Island along the Hamakua coast and around South Point where moderate to fresh southeast winds will continue. In addition to the winds, a few heavy showers and even a thunderstorm or two will be possible tonight through Tuesday night over the Kauai and Oahu waters as the front nears Kauai. A return of moderate to fresh easterly trades will be possible for all waters through the second half of the week.
Surf along north facing shores will hold steady today due to a persistent short-to-medium period mix of north-northwest to north-northeast energy moving through. As this energy eases into Tuesday, a medium-period, moderate northwest swell from a nearby source should arrive and begin to build down the island chain Tuesday night through Wednesday. This will be a long-lived event that should hold into next weekend as it shifts out of a more north-northwest direction.
Surf along south facing shores will remain up today, then trend down Tuesday through midweek as the south-southwest swell eases. A similar south-southwest swell will be possible later in the week.
Surf along east facing shores will remain small through the week.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov

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