Photo Credit: Sebastien Gabriel

West Kaua’i

Today: Mostly sunny. Scattered showers early in the morning, then isolated showers in the late morning and afternoon. Highs 78 to 87 near the shore to around 72 above 3000 feet. Northeast winds up to 10 mph shifting to the south in the afternoon. Chance of rain 50 percent.

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 65 to 70 near the shore to around 58 above 3000 feet. Northeast winds up to 10 mph. Chance of rain 50 percent.

Wednesday: Mostly sunny with isolated showers. Highs 77 to 85 near the shore to around 71 above 3000 feet. North winds up to 10 mph. Chance of rain 20 percent.

South Kaua’i

Today: Breezy. Partly sunny with scattered showers. Highs 78 to 85. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 68. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Wednesday: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs 77 to 84. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Kaua’i Mountains

Today: Mostly cloudy. Numerous showers early in the morning, then scattered showers in the late morning and afternoon. Highs 72 to 79 in the valleys to around 64 above 4000 feet. East winds up to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Numerous showers in the evening, then frequent showers after midnight. Lows 58 to 68 in the valleys to around 56 above 4000 feet. East winds up to 10 mph. Chance of rain 80 percent.

Wednesday: Mostly cloudy. Frequent showers in the morning, then scattered showers in the afternoon. Highs 72 to 78 in the valleys to around 63 above 4000 feet. East winds up to 10 mph. Chance of rain 80 percent.

North Kaua’i

Today: Partly sunny. Numerous showers early in the morning, then scattered showers in the late morning and afternoon. Highs 73 to 82. East winds up to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 61 to 69. East winds up to 10 mph. Chance of rain 70 percent.

Wednesday: Partly sunny with scattered showers. Highs 74 to 81. East winds up to 15 mph. Chance of rain 50 percent.

East Kaua’i

Today: Mostly cloudy. Numerous showers early in the morning, then scattered showers in the late morning and afternoon. Highs 71 to 82. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 62 to 72. Northeast winds up to 10 mph. Chance of rain 70 percent.

Wednesday: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 71 to 82. East winds up to 10 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

Moderate easterly trade winds will persist through midweek, with clouds and brief showers favoring windward and mauka areas. A cold front and upper disturbance approaching and moving into the area Thursday through Friday will disrupt the trades, potentially bringing another round of showers and thunderstorms to parts of the state. While residual moisture may keep rain chances in the forecast into Saturday, a more stable and dry air mass, along with a return of northeast trade winds, is possible by the end of the weekend.

Discussion

Short-term guidance remains in reasonable agreement through midweek, indicating rising upper heights over the region as the broad upper trough continues eastward and away from the state. Moderate trades will gradually weaken into the light to moderate range tonight through Wednesday as the surface ridge weakens and shifts southward, due to a front passing to the north. This setup will result in a mostly stable and dry trade wind pattern, with the best chances for showers in windward and mauka areas during the overnight and early morning hours.
Confidence in increasing with better model alignment, depicting the trades will be disrupted beginning Thursday as a cold front approaches and moves into the area. Increasing moisture and instability associated with lowering upper heights and the front will elevate the potential for showers and thunderstorms. Although most of the deep moisture and dynamics associated with this system will remain north of the state, some locally heavy rainfall and stronger storms interacting with island terrain will be possible.
By the weekend, the upper-level trough is expected to move east of the state, with ridging building in its wake, leading to more dry/stable conditions. Remnant moisture from the dissipating front may sustain rain chances into Saturday, though rainfall amounts should be minimal as the upper ridge becomes more established. Northeast trade winds could return by the end of the weekend as high pressure builds north of the area in the wake of the front.

Aviation

Moderate trades expected through Wednesday as a cold front passes north of Hawaii. Winds will focus low cigs and SHRA over windward and mauka areas. MVFR conds can be expected in SHRA but otherwise VFR should prevail.
AIRMET Sierra continues for mtn obsc for windward Big Island. Conds are slowly improving and this AIRMET will likely be dropped at next issuance.

Marine

Trade winds look to remain moderate to fresh through Tuesday before easing slightly Wednesday as the ridge to the north weakens and a front passes by to the north. A light wind regime is expected by Thursday through the end of the week as a potential cold front moves down the island chain. Associated with the front, an upper level trough may increase the potential for thunderstorms and numerous showers in the offshore and coastal waters as the front moves in from the northwest Thursday night and Friday.
The current moderate long-period northwest swell will continue to fill in overnight, peaking early Tuesday morning before slowly declining through the week. The High Surf Advisory (HSA) is currently in effect for north and west facing shores of Niihau, Kauai, Oahu, and Molokai and north facing shores of Maui through Tuesday.
A large long period northwest swell is expected to build Friday into Saturday from a closer, stronger storm that tracks generally towards the islands over the next few days. A High Surf Warning (HSW) is likely as satellite altimeter passes over the storm is already showing 40 foot seas. Through the first half of next week, a medium period northwest swell will likely fill in Monday keeping surf heights elevated over the forecast period.
Surf along south facing shores will remain very small through Wednesday. A moderate long period south swell is expected to start filling in Thursday, peak on Friday and slowly ease over the weekend. PacIOOS buoy observations located in Aunu'u, American Samoa is running above guidance suggesting surf may peak just below High Surf Advisory levels. Surf along east facing shores will hold relatively steady tonight then continue to decline through the end of the week. A small north swell could potentially elevate exposed shorelines Wednesday and Thursday.

Fire weather

No critical fire conditions anticipated during the forecast period.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 PM HST this evening 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 this evening for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Kaiwi Channel, Maui County Windward Waters.

Kauai Now Weather is brought to you by Blue Hawaiian Helicopters.