Photo Credit: James Grenz

Hilo

Today: Cloudy with occasional showers and slight chance of thunderstorms. Locally heavy rainfall possible. Highs 71 to 77 near the shore to 57 to 62 at 4000 feet. Northeast winds 10 to 15 mph. Chance of rain 90 percent.

Tonight: Cloudy with occasional showers. Lows 59 to 67 near the shore to 51 to 56 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 90 percent.

Thursday: Cloudy with occasional showers. Highs 71 to 77 near the shore to 56 to 62 at 4000 feet. East winds 10 to 15 mph. Chance of rain 90 percent.

Kona

Today: Mostly cloudy with showers likely and slight chance of thunderstorms. Locally heavy rainfall possible. Highs 77 to 82 near the shore to around 62 near 5000 feet. Light winds. Chance of rain 70 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 66 to 71 near the shore to 45 to 53 near 5000 feet. Light winds. Chance of rain 50 percent.

Thursday: Sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs around 80 near the shore to around 61 near 5000 feet. Light winds. Chance of rain 50 percent.

Waimea

Today: Breezy. Cloudy with occasional showers and slight chance of thunderstorms. Locally heavy rainfall possible. Highs 56 to 76. East winds 10 to 20 mph. Chance of rain 90 percent.

Tonight: Mostly cloudy with occasional showers. Lows 59 to 65 near the shore to 51 to 60 near 3000 feet. East winds 10 to 15 mph. Chance of rain 90 percent.

Thursday: Mostly cloudy. Breezy. Occasional showers in the morning, then showers likely in the afternoon. Highs 56 to 77. East winds 10 to 20 mph. Chance of rain 90 percent.

Kohala

Today: Breezy. Cloudy with occasional showers and slight chance of thunderstorms. Locally heavy rainfall possible. Highs 56 to 76. East winds 10 to 20 mph. Chance of rain 90 percent.

Tonight: Mostly cloudy with occasional showers. Lows 59 to 65 near the shore to 51 to 60 near 3000 feet. East winds 10 to 15 mph. Chance of rain 90 percent.

Thursday: Mostly cloudy. Breezy. Occasional showers in the morning, then showers likely in the afternoon. Highs 56 to 77. East winds 10 to 20 mph. Chance of rain 90 percent.

South Big Island

Today: Cloudy and breezy. Occasional showers and slight chance of thunderstorms in the morning, then showers likely and slight chance of thunderstorms in the afternoon. Locally heavy rainfall possible. Highs around 78 near the shore to around 61 near 5000 feet. East winds 10 to 20 mph. Chance of rain 80 percent.

Tonight: Mostly cloudy with isolated showers in the evening, then partly cloudy after midnight. Lows around 68 near the shore to around 49 near 5000 feet. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Thursday: Sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs around 77 near the shore to around 61 near 5000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Puna

Today: Cloudy with occasional showers and slight chance of thunderstorms. Locally heavy rainfall possible. Highs 71 to 77 near the shore to 57 to 62 at 4000 feet. Northeast winds 10 to 15 mph. Chance of rain 90 percent.

Tonight: Cloudy with occasional showers. Lows 59 to 67 near the shore to 51 to 56 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 90 percent.

Thursday: Cloudy with occasional showers. Highs 71 to 77 near the shore to 56 to 62 at 4000 feet. East winds 10 to 15 mph. Chance of rain 90 percent.

Waikoloa

Today: Mostly cloudy with showers likely and slight chance of thunderstorms. Locally heavy rainfall possible. Highs 75 to 82 near the shore to 60 to 65 above 4000 feet. Northeast winds up to 10 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy in the evening then becoming mostly clear. Isolated showers. Lows 66 to 71 near the shore to 46 to 52 above 4000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Thursday: Sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 76 to 82 near the shore to 60 to 65 above 4000 feet. Northeast winds up to 10 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Breezy and showery trade wind weather will trend a little drier tonight and Thursday, with just a few brief windward showers anticipated Friday and Christmas Day. Trade winds will ease somewhat by Christmas Day, then veer to the southeast and strengthen Sunday and Monday, when the potential for unsettled weather increases again.

Discussion

Breezy and rather wet trade wind weather continues this morning, as a slow-moving and very strong surface high sits far N of the islands, while a pair of mid- to upper-level troughs support an unstable atmosphere. Layered mid- and high-level clouds associated with a negatively-tilted trough passing S of the Big Island covers island skies from Oahu to the Big Island. Strong difluence aloft associated with this trough is leading to widespread rainfall over windward Maui and Big Island, with an isolated thunderstorm currently parked right off the Kona coast. Meanwhile, increased low- level moisture associated with a dissipated front is embedded within the trade flow.
The negatively tilted trough passing S of the islands will move E away from the islands by tonight, but will continue to support widespread lift over the Big Island into this afternoon, and the Flood Watch and Winter Weather Advisory have been extended. Windward areas on all islands will continue to experience active showers, with fast-moving showers periodically blowing across leeward sections.
Moderate to locally breezy trade winds and a somewhat typical pattern of windward and mauka showers is expected for Thursday through Christmas holiday weekend. Model guidance depicts a band of increased low-level moisture remaining offshore, but lurking just S of the islands, with some guidance indicating it could periodically clip the Big Island through the end of the week, potentially leading to increased windward showers. High pressure will hold far N of the state and will maintain moderate to locally breezy trade winds. Drier mid-level air will push down from the N, but the atmosphere will remain slightly unstable as upper level troughing lingers overhead.
On Saturday and Sunday, another kona low is expected to develop about 1000 miles NW of the islands, and then move S along ~175W into the middle of the week before moving W. Forecast models have lacked run-to-run consistency, but latest trends have been toward a wetter solution for the islands. A convergence band will likely be approaching Kauai from the W on Sunday, and the evolution of this feature is where model guidance diverges through the middle of next week, but it could spread over all islands at times through midweek, bringing the potential for heavy rainfall. Winds are expected to veer to the SE as the low surface low draws closer Sunday, which tends to place the smaller islands in the wind “shadow” of the Big Island, with lighter winds over land. However, strong high pressure will remain in place far N of the islands, and locally strong SE winds are possible in exposed areas. Potential impacts are highly dependent on where the low eventually develops and moves, thus we’ll be watching for consistency in model guidance to increase forecast confidence.

Aviation

A strong high pressure system far north of the state will keep breezy to locally strong trade winds blowing across the region through Thursday morning. Wind speeds will gradually trend lower by Thursday afternoon. An upper level disturbance lingering over the region will keep wet and unstable weather conditions in the forecast into Thursday. Periods of MVFR conditions remain in the forecast with scattered to numerous showers. Isolated thunderstorms are also possible near the Big Island through tonight. Drying weather trends are forecast to begin by Thursday afternoon for most areas.
AIRMET Sierra for tempo mountain obscuration due to low clouds in showers over north through east sections of Kauai, Oahu, Molokai, Maui and the Big Island.
AIRMET Tango for low level moderate turbulence remains in effect below 025 over mountains and south through west of all islands. A SIGMET for Severe Turbulence also remains in effect for a large area around Maui County and the Big Island, see SIGMET Uniform for further details.
AIRMET Zulu for moderate icing continues for Maui County to the Big Island including adjacent waters due to mid level cloud ceilings.

Marine

A strong 1037 mb surface high centered far north of the islands, will maintain moderate to strong trade winds across the main Hawaiian Islands area through Friday. A Small Craft Advisory (SCA) remains posted through for all Hawaiian Coastal Waters through late Thursday afternoon due to these strong winds and associated seas. An extension to the SCA is possible into Friday.
On Saturday, the trade winds will briefly subside to locally strong, leading to a possible reduction of the coverage to the SCA. On Sunday, with a gale- force surface low and front stalling west of Kauai, the trade winds will shift to the southeast across the western islands and strengthen to moderate to strong area- wide, resulting in the expansion of the SCA. Instability from an upper level low will threaten the western offshore and coastal waters with heavy showers and thunderstorms Sunday through at least Monday. In the meantime, an upper level trough will maintain the threat of heavy showers and thunderstorms over the south and western waters through Friday night.
A High Surf Advisory (HSA) is in effect through late this afternoon for the east facing shores from an elevated north- northeast swell. There is a possible extension to this advisory into Thursday. North facing shores will also experience surf heights just below HSA levels due to its higher criteria. This swell will lower very slightly Thursday then hold through Friday before resuming a slow decline over the weekend. Expect surf heights to stay at HSA levels for east facing shores.
Except for a moderate west-northwest pulse on Monday, swells from the northwest will be well below seasonal levels for this time of year. South facing shores will remain small throughout the forecast period with just background swell energy expected.

HFO Watches/Warnings/Advisories

Winter Weather Advisory until 6 PM HST this evening Big Island Summits.
Flood Watch until 6 PM HST this evening for the Big Island.
High Surf Advisory until 6 PM HST this evening for East facing shores of Kauai Oahu Molokai Maui and the Big Island.
Small Craft Advisory until 6 PM HST Thursday for all Hawaiian waters.

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Data Courtesy of NOAA.gov