Photo Credit: Tyler Rooke

West Side

Today: Sunny. A 20 percent chance of showers in the afternoon. Highs 73 to 81. North winds around 10 mph.

Tonight: Mostly clear. Lows 64 to 70. Northeast winds around 10 mph.

Saturday: Sunny. Highs 73 to 82. Northeast winds 10 to 15 mph.

South Side

Today: Mostly sunny. A 20 percent chance of showers in the afternoon. Highs around 83. North winds around 10 mph.

Tonight: Mostly clear. Lows 62 to 70. Northeast winds 10 to 15 mph.

Saturday: Sunny. Highs around 84. North winds 10 to 15 mph.

North Shore

Today: Sunny in the morning, then partly sunny with a 20 percent chance of showers in the afternoon. Highs 74 to 79 near the shore to around 63 near 5000 feet. Light winds.

Tonight: Mostly clear. Lows around 67 near the shore to 46 to 52 near 5000 feet. Light winds becoming northwest around 10 mph after midnight.

Saturday: Mostly sunny with a 20 percent chance of showers. Highs 74 to 79 near the shore to around 64 near 5000 feet. North winds around 10 mph.

Central Maui

Today: Mostly sunny. A 20 percent chance of showers in the afternoon. Highs around 80. North winds around 10 mph.

Tonight: Mostly clear. Lows 62 to 68. North winds around 10 mph.

Saturday: Sunny. Highs 78 to 83. North winds 10 to 15 mph.

Upcountry

Today: Mostly sunny. A 20 percent chance of showers in the afternoon. Highs around 59 at the visitor center to around 54 at the summit. Light winds.

Tonight: Mostly clear. Lows around 45 at the visitor center to around 41 at the summit. Light winds.

Saturday: Sunny with a 20 percent chance of showers. Highs around 60 at the visitor center to around 55 at the summit. Light winds.

East Maui

Today: Sunny in the morning, then partly sunny with a 20 percent chance of showers in the afternoon. Highs 74 to 79 near the shore to around 63 near 5000 feet. Light winds.

Tonight: Mostly clear. Lows around 67 near the shore to 46 to 52 near 5000 feet. Light winds becoming northwest around 10 mph after midnight.

Saturday: Mostly sunny with a 20 percent chance of showers. Highs 74 to 79 near the shore to around 64 near 5000 feet. North winds around 10 mph.

Lanai City

Today: Mostly sunny. A 20 percent chance of showers in the afternoon. Highs 70 to 78. Light winds becoming northwest around 10 mph in the afternoon.

Tonight: Mostly clear. Lows around 62. North winds around 10 mph.

Saturday: Mostly sunny. A 20 percent chance of showers in the afternoon. Highs 70 to 78. Light winds becoming northeast around 10 mph in the afternoon.

Kaunakakai

Today: Mostly sunny. A 20 percent chance of showers in the afternoon. Highs 63 to 82. North winds around 10 mph.

Tonight: Mostly clear. Lows 54 to 70. North winds around 10 mph.

Saturday: Sunny with a 20 percent chance of showers. Highs 64 to 83. Northeast winds 10 to 15 mph.

Detailed Forecast

Synopsis

The prevailing light winds and mostly dry weather will occasionally be interrupted by frontal passages that bring brief increases in winds and showers over the next week. The first front is expected to be weak and shallow, affecting only Kauai and Oahu late tonight and Saturday. Additional fronts are anticipated next week, and may affect all islands.

Discussion

A strong, zonal Pacific jet will drive weather features rapidly eastward over the next week, with low pressure dominating the north Pacific N of 30N. This storm track will ensure that the subtropical ridge remains shunted southward to near the latitude of the islands, which (generally speaking), will keep the islands in a region of light winds favorable for sea and land breeze development, with some variations on this theme. Mid-level ridging will limit shower intensity, but occasional low-level moisture surges will fuel increases in shower coverage.
As far as the details, confidence wanes in the longer range as timing the fast-moving features becomes increasingly difficult. In the shorter term, a trough just E of the Big Island will support low clouds, and a few showers, over windward Big Island and near shore waters into Saturday. With a weak cold front approaching from the NW, and a surface ridge extending over the area from W, the light NE winds currently over most of the area will switch to the W and NW later today and tonight. These light winds will allow sea breeze convergence to drive the formation of interior clouds and a few showers this afternoon, with the large-scale flow tending to push them toward the S and E.
Clearing land breezes are expected in most areas tonight, but a weak and shallow cold front riding in on light to moderate NW winds will move over Kauai late tonight, potentially bringing an increase in showery low clouds. The front is expected to move to Oahu on Saturday, fueling a modest increase in showery low clouds, then stall and dissipate in place Saturday night and Sunday. Winds will become light and variable as an E-W oriented surface ridge settles over the islands, with a mostly dry land-sea breeze pattern prevailing Saturday night and Sunday.
Sunday night and Monday, another cold front approaching from the NW will lead to increasing S to SW winds, with some showers developing over the islands in the weakly convergent low-level flow. The front is anticipated to move across the islands Monday night and Tuesday, once again bringing a somewhat short-lived increase in showery low clouds, and moderate to locally strong NW winds that veer to the NE late Tuesday. Winds are then expected to quickly veer to the SE and weaken on Wednesday as yet another front approaches. The evolution of this front, and weather details beyond that time, is highly uncertain, but we generally expect fast-moving weather systems to support a somewhat dynamic weather regime.

Aviation

A ridge of high pressure stretched across the islands will continue to generate a light and variable wind pattern across much of the state over the next few days. This pattern will allow for diurnal land and sea breezes, with afternoon cloud cover decreasing during the evenings. Mostly VFR conditions are expected through Friday, however isolated MVFR ceilings are possible through the evenings. Current radar trends and surface obs continue to show limited shower activity across the state, with chances for showers expected to remain small through this afternoon. However, the chance for showers increases slightly over the Big Island, Kauai, and Oahu tonight through Saturday, as a cold front and trough pass near the islands. No AIRMETs are currently in effect or anticipated through tonight.

Marine

Cold frontal systems passing north of the region will continue to keep the Central Pacific ridge in a weakened state with light winds continuing through the weekend. Expect land and sea breezes to continue for all near-shore island waters through Monday due to these light large scale wind speeds. High pressure will briefly strengthen north of the islands behind a cold front passing through the area on Tuesday.
A series of storm to hurricane force lows moving through the West Pacific basin will set up a long fetch directed towards the Hawaiian Island chain. This pattern will generate three rather large northwest swells into the Hawaii region over the next seven days. The latest marine guidance shows that each of these swells will exceed high surf advisory levels lasting into the middle of next week with periods of high surf exceeding warning thresholds along north and west facing shores. The latest model guidance shows these swells coming into the islands from a 310 direction.
The current large northwest swell will continue to decline today with seas falling below Small Craft Advisory (SCA) level today. Although the SCA was cancelled this morning expect elevated seas to continue for northern coastal waters just below SCA thresholds. The current northwest swell will gradually decline through tonight, the High Surf Advisory will continue for north and west facing shores of Kauai County, Oahu, and Molokai; including north facing shores of Maui, and west facing shores of the Big Island until this evening.
The next large northwest swell will build into the region from later tonight into Saturday, likely exceeding High Surf Advisory (HSA) thresholds from late Friday night onward, and exceeding High Surf Warning (HSW) thresholds from Saturday afternoon into Sunday.
On Monday, as this first northwest swell begins to decline into HSA levels, a second larger northwest swell builds into the region. This new northwest swell will quickly build north and west facing surf heights above HSW levels from Monday night into Wednesday. Yet another large northwest swell builds into the region by Wednesday night, once again pumping up surf heights for exposed north and west facing shores above HSW levels, just as the second northwest swell starts to decline.
Light to gentle winds will keep surf heights low along east facing shores this week. South swell activity also remains nearly flat.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 PM HST this evening for north and west facing shores of Niihau Kauai Oahu and Molokai and for north facing shores of Maui and for west facing shores of the Big Island.

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Data Courtesy of NOAA.gov