West Side

Today: Mostly cloudy. Breezy. Isolated showers in the morning, then scattered showers in the afternoon. Highs 73 to 84. East winds 10 to 20 mph. Chance of rain 40 percent.

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 63 to 71. East winds 10 to 15 mph. Chance of rain 40 percent.

Wednesday: Partly sunny in the morning then becoming mostly sunny. Isolated showers. Highs 72 to 83. East winds 10 to 15 mph. Chance of rain 20 percent.

South Side

Today: Mostly cloudy. Isolated showers in the afternoon. Highs 74 to 85. North winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Lows 64 to 69. North winds up to 10 mph.

Wednesday: Mostly sunny. Highs 74 to 84. North winds up to 15 mph shifting to the northeast in the afternoon.

North Shore

Today: Breezy. Showers in the morning, then scattered showers in the afternoon. Highs 76 to 81 near the shore to around 64 near 5000 feet. East winds 10 to 20 mph. Chance of rain near 100 percent.

Tonight: Cloudy with numerous showers. Lows around 69 near the shore to around 51 near 5000 feet. Southeast winds up to 15 mph. Chance of rain 70 percent.

Wednesday: Mostly cloudy. Showers in the morning, then scattered showers in the afternoon. Highs around 78 near the shore to around 63 near 5000 feet. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 60 percent.

Central Maui

Today: Breezy. Cloudy with scattered showers. Highs 79 to 85. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with isolated showers. Lows 64 to 69. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Wednesday: Partly sunny with isolated showers in the morning, then mostly sunny in the afternoon. Highs 79 to 84. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Upcountry

Today: Cloudy with scattered showers. Highs 50 to 68. East winds up to 15 mph. Chance of rain 50 percent.

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

Wednesday: Mostly sunny in the morning then becoming partly sunny. Breezy. Scattered showers. Highs 50 to 67. East winds up to 20 mph. Chance of rain 50 percent.

East Maui

Today: Breezy. Showers in the morning, then scattered showers in the afternoon. Highs 76 to 81 near the shore to around 64 near 5000 feet. East winds 10 to 20 mph. Chance of rain near 100 percent.

Tonight: Cloudy with numerous showers. Lows around 69 near the shore to around 51 near 5000 feet. Southeast winds up to 15 mph. Chance of rain 70 percent.

Wednesday: Mostly cloudy. Showers in the morning, then scattered showers in the afternoon. Highs around 78 near the shore to around 63 near 5000 feet. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 60 percent.

Lanai City

Today: Partly sunny in the morning, then cloudy with scattered showers in the afternoon. Highs 68 to 78. Northeast winds up to 15 mph. Chance of rain 40 percent.

Tonight: Mostly cloudy in the evening then becoming mostly clear. Lows 58 to 65. Northeast winds up to 10 mph.

Wednesday: Sunny in the morning, then mostly cloudy with isolated showers in the afternoon. Highs 67 to 78. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Kaunakakai

Today: Mostly cloudy. Isolated showers in the morning, then scattered showers in the afternoon. Highs 66 to 84. East winds 10 to 15 mph. Chance of rain 40 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 55 to 71. East winds 10 to 15 mph. Chance of rain 40 percent.

Wednesday: Partly sunny. Breezy. Isolated showers in the morning. Highs 65 to 83. East winds 10 to 20 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A trough associated with the dissipated cold front northwest of Kauai will continue to drift northwestward away from the islands. The high pressure ridge will build back in from the north through the afternoon hours with winds shifting from a more easterly direction. A brief period of enhanced showers will develop over each island as these breezy trade winds return. The next round of enhanced showers will move in from the north, along a backdoor cold front, from Thursday night through at least Friday. Some of these enhanced cloud and shower trends may linger into early Saturday. Drier island weather trends from Sunday to Monday.

Discussion

The big picture satellite imagery appears rather cloudy this morning, as the subtropical jet stream spreads an abundance of high level cirrus and mid level altocumulus clouds across the entire state. In the low levels a weakening trough, associated with a dissipated cold front, northwest of Kauai will continue to lift northwestward away from the islands. This diminishing trough will allow the high pressure ridge to build back into the islands from the north. The current east-southeasterly wind regime will be swiftly replaced by moderate to breezy easterly winds. A cloud band likely produced by the convergence of these stronger easterly winds will slowly move into the eastern or windward slopes of the Big Island over the next several hours. Expect this cloud band to drift westward throughout the day, briefly enhancing clouds and showers as it passes through each island. This cloud band moves through the Big Island and Maui this morning, reaching Molokai and Oahu around noon HST, and finally passing through the western islands of Kauai and Niihau through the afternoon hours.
High pressure aloft will produce stable conditions and keep fair weather in the forecast from New Year's Eve through New Years Day with only brief passing showers, mainly over windward and mountain areas in the overnight to early morning time periods. Moderate to locally breezy easterly trade winds will continue to blow through New Year's day, keeping the fireworks smoke from settling in.
Another round of enhanced showers will move in from the north, along a backdoor cold front, from Thursday night through at least Friday. THese cloud and shower trends from this frontal band may linger into early Saturday for some areas. Global weather model solutions are uncertain on the ending of this period of this enhanced shower activity. The American (GFS) model shows the frontal band stalling over the islands, a longer duration wet trade wind solution. While the European (ECMWF) model builds a stronger high pressure system just north of the state, driving this frontal band quickly through the region, a shorter duration and drier solution. We decided to take a blend of operational models for this medium range forecast, however our confidence remains only moderate on precisely when these enhanced showers will end over each island this weekend. Drier island weather trends should return across the region from Sunday into early next week.

Aviation

East-southeasterly large scale winds will become more easterly and strengthen later today as a wind convergence cloud band drifts from east to west down the island chain. Expect a brief period of enhanced showers as this smaller scale band passes through each island. Mostly VFR conditions will prevail, except brief periods of MVFR conditions in showers as the convergent cloud band moves through the Big Island and Maui this morning, then Molokai and Oahu around noon HST, and finally reaching Kauai and Niihau by the early afternoon hours.
AIRMET Sierra for mountain obscurations may be needed over windward areas from Big Island to Oahu later this morning as a band of clouds and showers moves through the region.

Marine

Moderate to locally strong easterly trade winds return to the coastal waters today and will continue through the week as high pressure builds north of the islands. A Small Craft Advisory remains in effect for the typically windy waters around Maui County and the Big Island, and has been extended in time through Wednesday afternoon.
Overlapping moderate to large, medium period northwest (320-340 degree) and north-northwest (340-350 degree) swells will maintain advisory-level surf with very minor fluctuations through Wednesday. Recent buoy observations show that this swell is running around 2 feet above guidance at this time, so have maintained the High Surf Advisory for north and west facing shores of Niihau, Kauai, Oahu, Molokai, and north facing shores of Maui, and extended it in time through the day on Wednesday. This swell will then gradually decline from late Wednesday through the rest of the week, with surf falling back below advisory criteria at that time. Additionally, seas could flirt with 10 ft Small Craft Advisory criteria across exposed waters during the peak of the swell, but have maintained a max of 9 feet (just under SCA seas criteria) in the forecast at this time based on latest guidance and buoys.
Choppy east shore surf will continue though mid-week as locally breezy trade winds strengthen. Surf along south facing shores will remain tiny to small through the forecast period.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 PM HST Wednesday for Niihau, Kauai Leeward, Waianae Coast, Oahu North Shore, Maui Windward West, Kauai North, Molokai Windward, Molokai North, Molokai West, Maui Central Valley North, Windward Haleakala.
Small Craft Advisory until 6 PM HST Wednesday for Pailolo Channel, Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov