Photo Credit: Tyler Rooke

West Side

Today: Sunny, with a high near 87. East northeast wind 6 to 14 mph, with gusts as high as 18 mph.

Tonight: Clear, with a low around 69. Breezy, with an east northeast wind 10 to 17 mph, with gusts as high as 24 mph.

Christmas Day: Sunny, with a high near 85. Breezy, with an east wind 5 to 10 mph increasing to 11 to 16 mph in the afternoon. Winds could gust as high as 22 mph.

South Side

Today: Partly sunny, with a high near 82. Calm wind becoming west around 6 mph in the afternoon.

Tonight: Mostly clear, with a low around 66. Light north northeast wind.

Christmas Day: Isolated showers after noon. Sunny, with a high near 82. West wind around 6 mph becoming calm in the afternoon. Chance of precipitation is 20%.

North Shore

Today: Sunny, with a high near 82. Breezy, with an east wind 10 to 17 mph, with gusts as high as 24 mph.

Tonight: Isolated showers after midnight. Partly cloudy, with a low around 68. Breezy, with an east wind 14 to 17 mph, with gusts as high as 24 mph. Chance of precipitation is 20%.

Christmas Day: Isolated showers before 1pm. Sunny, with a high near 82. Breezy, with an east wind 14 to 20 mph, with gusts as high as 28 mph. Chance of precipitation is 20%.

Central Maui

Today: Sunny, with a high near 83. Northeast wind 6 to 14 mph, with gusts as high as 18 mph.

Tonight: Mostly clear, with a low around 68. Northeast wind 6 to 9 mph.

Christmas Day: Sunny, with a high near 83. Breezy, with a northeast wind 7 to 16 mph, with gusts as high as 22 mph.

Upcountry

Today: Mostly sunny, with a high near 71. Calm wind becoming west around 6 mph in the afternoon.

Tonight: Mostly clear, with a low around 54. Calm wind.

Christmas Day: Sunny, with a high near 70. Calm wind becoming west around 5 mph.

East Maui

Today: Scattered showers. Partly sunny, with a high near 78. North northeast wind 5 to 7 mph. 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 70. East wind around 6 mph becoming calm in the evening. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Christmas Day: Scattered showers. Partly sunny, with a high near 78. East southeast wind 5 to 9 mph becoming calm in the afternoon. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Lanai City

Today: Isolated showers. Mostly cloudy, with a high near 75. Breezy, with a northeast wind 10 to 15 mph, with gusts as high as 21 mph. Chance of precipitation is 10%.

Tonight: Mostly cloudy, then gradually becoming mostly clear, with a low around 63. Northeast wind 7 to 14 mph, with gusts as high as 18 mph.

Christmas Day: Isolated showers after noon. Sunny, with a high near 75. Northeast wind 8 to 11 mph. Chance of precipitation is 20%.

Kaunakakai

Today: Sunny, with a high near 87. East wind 6 to 13 mph.

Tonight: Mostly clear, with a low around 71. East wind 11 to 14 mph, with gusts as high as 18 mph.

Christmas Day: Sunny, with a high near 85. Breezy, with an east northeast wind 14 to 16 mph, with gusts as high as 22 mph.

Detailed Forecast

Synopsis

Trade winds are in the process of returning, and will be trending stronger into Saturday as a surface high pressure system passes north of the islands. Showery weather is expected for Kauai on Friday, and for the island of Oahu and maybe windward Maui County on Saturday, as a front eases over and falls apart over the northern islands. Trade winds will then trend down and turn southeast over the western islands early next week due to an approaching front.

Discussion

Well ahead of a front just off Oahu’s north shore is an area of clouds and embedded showers. This area appears to be expanding into the Kauai Channel, and will be the supplier for some trade wind showers for both Kauai and Oahu today.
As of 3 am HST, the front is 60 miles NW of Kauai. The front is moving towards Kauai, but is expected to slow down in the coming hours. The front is not expected to move onshore of northern Kauai until this evening. But its cloud mass will likely mesh in with the expanding area of moisture now in the Kauai Channel. The result is scattered windward showers for Kauai later this morning lingering well into Friday. Isolated to scattered showers are expected for north shore and windward Oahu. Maui County and the Big Island looks rather dry, and this trend will likely hold through the rest of today. The front is expected to start falling apart Saturday, upon reaching Oahu. From there on, remnants of the front will then spread on to Maui County. The models are suggesting an uptick in trade showers for windward Big Island on late Saturday night into Sunday.
The winds this morning will have a blend of NE to E trade winds, strengthening as the day progresses. Moderate to strong trade winds are expected to reach Kauai Friday afternoon, then parts of Maui and the Big Island Friday evening, spreading to Oahu Saturday, then to Maui County Saturday night. The strong trades are being generated by a passing 1031 mb surface high N of the islands Friday night and Saturday. Hence, Friday night through Saturday night is shaping up to be showery and windy for the smaller islands.
On Sunday, expect the trades to begin trending weaker, while the winds bend a little to the S across Kauai and Oahu on Sunday afternoon. Except for windward Big Island, the frequency of the showers will be becoming less as well. Light and variable winds are expected to settle across the western islands on Monday, while a drier moderate E to SE flow prevails across Maui and the Big Island. The light and variable winds will lead to a daytime sea breeze and a nighttime land breeze for most of the smaller islands. A stable air mass will likely limit the afternoon showers to isolated. This shift in the winds is the result of an approaching front. A series of fronts passing N of the islands will maintain this wind pattern through the middle of next week.
Vog produced by the eruption of the Kilauea Volcano/Halemaumau Crater continues to blow downwind across the Kau District, with some of it spilling onto the Kona districts. Significant impacts to air quality are not expected, but we are still learning about the concentrations of particulates associated with this new eruption.

Aviation

VFR conditions will dominate across much of the state today, with highest chances for MVFR ceilings and visibility on windward and northern Kauai. Surface high pressure nearing the region from the northwest will lead to increasing trade winds through the day. A band of clouds currently grazing northern Oahu will be carried westward on the building trade winds, likely producing isolated MVFR conditions on windward slopes of Kauai. A shallow front will advance toward the state and reach Kauai by evening, increasing chances for widespread MVFR conditions. Across the rest of the state, the dry and stable trade wind flow will maintain prevailing VFR conditions.
No AIRMETs are currently in effect.

Marine

A weakening cold front will shift southward toward Kauai today, finally moving onshore of northern Kauai this evening. It will remain over Kauai the rest of tonight and Christmas Day, then dissipate over the weekend. At the same time, a new strong high will build from west to east, several hundred miles north of the islands. As a result, we should see light to moderate trade winds begin to make a return today, with the trades strengthening heading into the weekend. In fact winds may reach Small Craft Advisory (SCA) levels tonight and Friday over the northwest Kauai waters. Winds will likely reach SCA levels across the windier areas around Maui and the Big Island Friday night through the weekend, with a few other marine zones possibly reaching SCA thresholds during this period as well. The trades should diminish back into the light to moderate range Monday and Tuesday as a cold front approaches from the northwest. Trades may then increase a bit by the middle of next week as the front stalls out and a new ridge of high pressure builds to the north of the island chain.
A SCA is now in effect for elevated seas across a large chunk of the marine area through 6 PM Friday due to the building northwest swell described below. Seas will remain at or above the 10 foot SCA threshold across portions of the marine area exposed to this northwest swell and a new northeast swell due in over the weekend, also described below. As a result, adjustments to the SCA duration will be needed as the timing of these swells becomes more clear.
A large long period northwest swell will continue to build from northwest to southeast down the island chain this morning, peak this afternoon into this evening, then slowly decline late tonight through the weekend. This swell appears to be running around 12 hours behind the WW3 forecast based on the latest available buoy observations. As a result, the High Surf Advisory for north and west facing shores of the smaller islands exposed to this swell has been extended through 6 AM Friday, and this may very well need to be extended right through Christmas Day. Additionally, west facing shores of the Big Island may see surf approach advisory levels tonight and Friday. North shore surf should then hold below advisory thresholds Friday night through Monday night, although a small reinforcing northwest swell will move through the islands Sunday through Monday. The next significant northwest swell appears to build on Tuesday, and may reach High Surf Warning levels along exposed north and west facing shores around the middle of next week.
An out-of-season long period south swell will continue to bring elevated surf to south facing shores today with a slow decline expected through Christmas Day. No other significant south swells are expected through the middle of next week.
East shore surf will remain small through Christmas Day, then build as a new northeast swell arrives Friday night and Saturday as the trades increase over and upstream of the islands. This northeast swell may boost east shore surf to near advisory levels Saturday night and Sunday, before declining Sunday night and Monday. East shore surf will then hold steady in the 3-5 foot range Monday night through the middle of next week.

HFO Watches/Warnings/Advisories

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

Data Courtesy of NOAA.gov