Photo Credit: Tyler Rooke

West Side

Today: Breezy. Mostly cloudy with scattered showers. Highs 71 to 79. Northeast winds 15 to 20 mph. Chance of rain 50 percent.

Tonight: Breezy. Partly cloudy with scattered showers. Lows 64 to 70. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Thursday: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 72 to 80. Northeast winds 10 to 20 mph. Chance of rain 40 percent.

South Side

Today: Breezy. Partly sunny with isolated showers. Highs around 81. Northeast winds 15 to 20 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Isolated showers after midnight. Lows 61 to 70. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Thursday: Sunny and breezy. Highs around 82. Northeast winds 10 to 20 mph.

North Shore

Today: Breezy. Cloudy with occasional showers. Highs 71 to 77 near the shore to around 59 near 5000 feet. East winds 15 to 20 mph. Chance of rain 90 percent.

Tonight: Breezy. Cloudy with occasional showers. Lows around 67 near the shore to 45 to 51 near 5000 feet. East winds 10 to 20 mph. Chance of rain 90 percent.

Thursday: Mostly cloudy. Breezy. Occasional showers in the morning, then showers likely in the afternoon. Highs 71 to 78 near the shore to around 60 near 5000 feet. East winds 10 to 20 mph. Chance of rain 90 percent.

Central Maui

Today: Breezy. Mostly cloudy with scattered showers. Highs around 77. Northeast winds 15 to 20 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with isolated showers. Lows 62 to 68. Northeast winds around 15 mph. Chance of rain 20 percent.

Thursday: Breezy. Mostly sunny with isolated showers. Highs 76 to 81. Northeast winds 15 to 20 mph. Chance of rain 20 percent.

Upcountry

Today: Mostly cloudy with scattered showers. Highs around 54 at the visitor center to around 50 at the summit. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with scattered showers. Lows around 43 at the visitor center to around 41 at the summit. East winds up to 10 mph increasing to 10 to 15 mph after midnight. Chance of rain 50 percent.

Thursday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 55 at the visitor center to around 51 at the summit. East winds up to 10 mph. Chance of rain 50 percent.

East Maui

Today: Breezy. Cloudy with occasional showers. Highs 71 to 77 near the shore to around 59 near 5000 feet. East winds 15 to 20 mph. Chance of rain 90 percent.

Tonight: Breezy. Cloudy with occasional showers. Lows around 67 near the shore to 45 to 51 near 5000 feet. East winds 10 to 20 mph. Chance of rain 90 percent.

Thursday: Mostly cloudy. Breezy. Occasional showers in the morning, then showers likely in the afternoon. Highs 71 to 78 near the shore to around 60 near 5000 feet. East winds 10 to 20 mph. Chance of rain 90 percent.

Lanai City

Today: Partly sunny. Breezy. Scattered showers in the morning, then showers likely in the afternoon. Highs 68 to 76. East winds 15 to 20 mph. Chance of rain 70 percent.

Tonight: Mostly clear. Breezy. Lows 59 to 64. Northeast winds 15 to 20 mph.

Thursday: Mostly sunny. Breezy. Isolated showers in the afternoon. Highs 69 to 77. East winds 15 to 20 mph. Chance of rain 20 percent.

Kaunakakai

Today: Breezy. Partly sunny with scattered showers. Highs 61 to 81. East winds 20 to 25 mph. Chance of rain 50 percent.

Tonight: Breezy. Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 54 to 70. East winds 20 to 25 mph. Chance of rain 50 percent.

Thursday: Breezy. Mostly sunny with isolated showers. Highs 62 to 82. East winds 20 to 25 mph. Chance of rain 20 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