Photo Credit: Braden Jarvis

West Kaua’i

Today: Sunny. Scattered showers in the morning. Highs around 82 near the shore to around 70 above 3000 feet. Light winds becoming southwest up to 10 mph in the afternoon. Chance of rain 40 percent.

Tonight: Mostly clear. Lows around 62 near the shore to around 56 above 3000 feet. Northeast winds up to 10 mph.

Friday: Sunny. Highs around 81 near the shore to around 69 above 3000 feet. Light winds.

South Kaua’i

Today: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 79. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Mostly clear. Isolated showers after midnight. Lows around 62. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Friday: Sunny. Isolated showers in the morning. Highs around 78. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Kaua’i Mountains

Today: Mostly cloudy with numerous showers in the morning, then mostly sunny with scattered showers in the afternoon. Highs 69 to 76 in the valleys to around 60 above 4000 feet. Northeast winds up to 15 mph. Chance of rain 70 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows 55 to 60 in the valleys to around 53 above 4000 feet. East winds up to 10 mph in the evening becoming light. Chance of rain 50 percent.

Friday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 68 to 75 in the valleys to around 59 above 4000 feet. Light winds becoming northeast up to 10 mph in the afternoon. Chance of rain 40 percent.

North Kaua’i

Today: Partly sunny with scattered showers in the morning, then sunny with isolated showers in the afternoon. Highs 72 to 81. Northeast winds up to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy. Isolated showers after midnight. Lows 57 to 63. Southeast winds up to 10 mph. Chance of rain 20 percent.

Friday: Sunny. Isolated showers in the morning. Highs 71 to 80. Southeast winds up to 10 mph. Chance of rain 20 percent.

East Kaua’i

Today: Mostly cloudy with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 72 to 80. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with isolated showers. Lows 53 to 64. Northeast winds up to 10 mph. Chance of rain 20 percent.

Friday: Sunny. Isolated showers in the morning. Highs 71 to 79. Northeast winds up to 10 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A weakening front moving through Kauai will reach Oahu and Maui County through the day, then the Big Island tonight as it begins to stall. A narrow band of clouds with embedded showers will accompany this boundary moving though, with much of the shower activity favoring north through east facing slopes and coasts. The northerly winds will shift out of the northeast through the day, then out of a more typical easterly trade wind direction Friday into the weekend. Trades will be disrupted on Sunday, and another front may affect the state on New Year's Day.

Discussion

Guidance remains in decent agreement through the weekend and shows the progressive pattern continuing over the northern Pacific, featuring a series of gale- to hurricane-force systems quickly advancing eastward while passing the islands to the north. Early morning satellite imagery showed the tail-end of a weakening front associated with a hurricane-force system passing north of the state moving through Kauai. Despite the stable and suppressed environment in place (subsidence inversions positioned around 5,000 ft), a band of moisture with PWs up to around 1.5 inches accompanying the boundary approaching will be enough to support a band of light showers. Early morning radar loop showed the leading edge of this narrow band of light showers moving through Kauai. Rain gauges on Kauai are showing a few hundredths up to a tenth over the past few hours.
With the breezy north to northeast winds in place today, expect the majority of shower coverage to focus over northern and eastern slopes and coasts. For timing, guidance shows this band of showers reaching Oahu and Maui County around through the day, then the Big Island tonight as the boundary begins to stall and diminish.
A brief return of a more typical easterly trade wind pattern (lighter winds over the western end of the state) is anticipated Friday through Saturday, with showers favoring windward areas. The surface ridge to the north is forecast to weaken and shift southward as another front approaches the region. Despite some model inconsistencies shown during this period, increasing moisture combined with falling upper heights support breezy northeasterly winds increasing rainfall chances on New Year's Day.

Aviation

A weak front moving through Kauai will bring scattered showers to the smaller islands today. By tonight, the front will bring increased showers to windward portions of the Big Island. Expect periods of MVFR ceilings and visibility associated with these passing showers.
Weak northerly flow will veer northeasterly and become breezy as the aforementioned front passes over the islands.
No AIRMETs are currently in effect.

Marine

The current large northwest swell will continue to trend down in the early morning hours. Surf heights along exposed north and west facing shores of the smaller islands have fallen near warning levels this morning but offshore buoys have begun to respond to the upcoming swell so a sharp rise up mid-morning through the day is expected. This will keep the High Surf Warning (HSW) in effect through at least tonight.
Seas have responded above Small Craft Advisory threshold for those waters around Kauai, Oahu, windward Maui County, Alenuihaha Channel, and windward Big Island. The SCA has been extended through Friday due to the elevated seas. The HSW may be extended through Friday depending on how long and high the swell comes in. Additionally, a High Surf Advisory for north facing shores of the Big Island may be added tonight through at least Saturday as the swell turns north-northeast.
Provided the long duration with large to extra large level surf expected over the next week, significant erosion along exposed north and west facing beaches should be anticipated. This erosion combined with our early morning high tides and warning-level surf could translate to overwash onto our vulnerable coastal roadways and impact properties periodically. The most likely time frames for these impacts will be this afternoon into Friday as next swell may be near its peak.
A mix of north (360-020 deg) and northwest (320 deg) swell energy impacting exposed beaches will likely support advisory-level surf by this weekend. For the extended, the northern Pacific looks to remain fairly active and will continue to send swell to the islands for the start of the 2024.
Surf along east facing shores will remain small through the week due to the light winds locally. East shores exposed to northerly swells will begin to pick up for today through the upcoming weekend as the swell direction shifts out of the north to north- northeast. Surf along south facing shores will remain around the winter average through the week.
The winds over the local waters will fluctuate from light and variable to moderate north to northeast as the tail-end of passing fronts clip the area. For timing, expect the light winds today, moderate north to northeast winds today, then moderate to locally strong trade winds that set up tonight, then ease slightly Friday and Saturday. Typical windy waters around Maui County and the Big Island may need to be added to the SCA for a brief time tonight into Friday.

HFO Watches/Warnings/Advisories

High Surf Warning until 6 AM HST Friday for Niihau, 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 AM HST Friday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Alenuihaha Channel, Big Island Windward Waters.

Data Courtesy of NOAA.gov