Hilo

Today: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 79 near the shore to 60 to 65 at 4000 feet. Northwest winds up to 10 mph shifting to the east in the afternoon. Chance of rain 40 percent.

Tonight: Mostly cloudy with scattered showers. Lows 60 to 66 near the shore to around 54 at 4000 feet. West winds up to 10 mph. Chance of rain 40 percent.

Christmas Day: Partly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 78 to 83 near the shore to 63 to 69 at 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Kona

Today: Sunny. Isolated showers in the afternoon. Highs around 83 near the shore to around 66 near 5000 feet. Light winds. Chance of rain 20 percent.

Tonight: Partly cloudy. Lows around 70 near the shore to 47 to 53 near 5000 feet. Light winds.

Christmas Day: Mostly sunny in the morning then becoming partly sunny. Highs around 84 near the shore to 65 to 70 near 5000 feet. Light winds.

Waimea

Today: Mostly sunny. Breezy. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 77 near the shore to 65 to 74 near 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 60 to 69 near the shore to 53 to 59 near 3000 feet. Southeast winds up to 10 mph. Chance of rain 50 percent.

Christmas Day: Partly sunny. Isolated showers in the afternoon. Highs around 77 near the shore to 67 to 75 near 3000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Kohala

Today: Mostly sunny. Breezy. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 77 near the shore to 65 to 74 near 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 60 to 69 near the shore to 53 to 59 near 3000 feet. Southeast winds up to 10 mph. Chance of rain 50 percent.

Christmas Day: Partly sunny. Isolated showers in the afternoon. Highs around 77 near the shore to 67 to 75 near 3000 feet. East winds up to 10 mph. Chance of rain 20 percent.

South Big Island

Today: Sunny and breezy. Isolated showers in the afternoon. Highs around 82 near the shore to around 64 near 5000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Lows around 70 near the shore to around 49 near 5000 feet. Northeast winds up to 15 mph.

Christmas Day: Mostly sunny in the morning then becoming partly sunny. Highs around 83 near the shore to around 65 near 5000 feet. Northeast winds up to 15 mph shifting to the southeast in the afternoon.

Puna

Today: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 79 near the shore to 60 to 65 at 4000 feet. Northwest winds up to 10 mph shifting to the east in the afternoon. Chance of rain 40 percent.

Tonight: Mostly cloudy with scattered showers. Lows 60 to 66 near the shore to around 54 at 4000 feet. West winds up to 10 mph. Chance of rain 40 percent.

Christmas Day: Partly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 78 to 83 near the shore to 63 to 69 at 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Waikoloa

Today: Sunny and breezy. Highs 80 to 85 near the shore to around 66 above 4000 feet. East winds up to 20 mph shifting to the north in the afternoon.

Tonight: Partly cloudy. Lows around 70 near the shore to 49 to 55 above 4000 feet. Southeast winds up to 10 mph.

Christmas Day: Mostly sunny. Highs around 82 near the shore to 64 to 70 above 4000 feet. Light winds.

Detailed Forecast

Synopsis

Generally clear skies and a dry weather pattern will persist through next week. A couple of decaying cold fronts will bring a modest increase in windward and mauka clouds and showers Tuesday then again Friday. Gentle to breezy trades will remain through the forecast period with minor fluctuations.

Discussion

This morning soundings show a drier and more stable atmosphere as the trade wind inversion has lowered to 6 kft around Hilo from 7.5 kft Saturday afternoon. The Lihue inversion remains around to 5 kft. In addition, precipitable water vapor from the soundings, confirm below average water vapor values of 1″ or less around the island chain. IR satellite imagery and local radar mosaic also confirms a drier more stable airmass with a rather low coverage of clouds and light showers early this morning. High clouds have thinned and moved south of the Big Island as the upper level trough moves east and a weak upper level ridge moves over the state. Trades are holding in the gentle to breezy range but should trend down later today as a surface ridge to the north drifts further south and a weak front approaches from the far northwest.
Forecast remains on track with stability remaining in place during the coming days as a strong zonal jet works its way across the Pacific Basin displacing the trade wind belt to the south and leaving the islands along its northern periphery where trades will mainly be of a light to moderate character. The entirety of the forecast period is likely to fall firmly on the drier-than- normal side of climatology. It is worth noting that the global guidance indicates two decaying frontal boundaries sagging through the area next week, the first on Tuesday and the second on Friday. The local environment characterized by high stability, a low inversion, active subsidence, and a dearth of any larger scale support, will be hostile to these frontal features and the forecast remains on the dry side as of now. Nothing more than a modest increase in light windward and mauka showers is anticipated during these periods.

Aviation

Moderate trades will persist today, then weaken slightly tonight.
Relatively dry air should remain in place today and limit shower activity. A few showers remain possible along windward locations with mainly dry weather and VFR conditions elsewhere.
There are currently no AIRMETs in effect.

Marine

Fresh to locally strong easterly trades will continue through today, then trend down this evening into Christmas Day as the surface ridge weakens to the north due to a passing front. A Small Craft Advisory (SCA) remains in effect for the typically windier waters around Maui County and the Big Island through this afternoon. The tail end of this front will slowly advance down the island chain late Monday through midweek. Light winds on Christmas Day will be followed by a shift out of the north in the moderate to fresh range over the western end of the state by that evening. North- northeast trades will briefly strengthen Tuesday to fresh to strong speeds, before shifting out of the east and trending down Tuesday night through midweek as another front approaches. Trade winds in the moderate to fresh range will then look to prevail for the rest of the week as a decaying frontal boundary is expected to approach the islands in the later part of the week.
A large long period north-northwest swell will continue to build this morning and peak later today. Long period energy has begun to fill in over nearshore PacIOOS Waimea Buoy 51201 over the last few hours and will continue. A High Surf Advisory (HSA) has been issued for select north and west facing shores through tonight. A Small Craft Advisory (SCA) may need to be issued if this swell continues to exceed guidance for seas greater than 10 feet but is unlikely at this time.
A series of back-to-back, High Surf Warning (HSW) level north- northwest swells will impact the islands this week. The first looks to gradually build in Tuesday and peak Tuesday night into Wednesday. Another reinforcing north-northwest swell, potentially even larger than the previous one, may fill in Thursday and peak Thursday night into Friday. Impacts to coastal properties, low- lying infrastructure including roadways may be impacted during both events as the swell peaks. Although confidence is low, guidance depicts this trend of progressive swells moving through the islands to continue into the new year.
Surf along east facing shores will steadily lower through the week as the trades ease. With the angle of the series of large north- northwest swells impacting the islands, areas exposed along east facing shores will see elevated surf. Surf along south facing shores will remain small through the middle of the week, as background south-southwest swells move through.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 AM HST Monday for north and west facing shores of Niihau, Kauai, Oahu, Molokai and north facing shores of Maui.
Small Craft Advisory until 6 PM HST this evening for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov