Photo Credit: Braden Jarvis

West Kaua’i

Today: Mostly sunny. Breezy. Isolated showers in the morning. Highs around 79 near the shore to around 67 above 3000 feet. Northeast winds up to 20 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Lows around 65 near the shore to around 54 above 3000 feet. Northeast winds 10 to 15 mph.

Sunday: Sunny in the morning then becoming partly sunny. Highs around 80 near the shore to around 67 above 3000 feet. Northeast winds 10 to 15 mph.

South Kaua’i

Today: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny in the afternoon. Highs 75 to 80. Northeast winds 15 to 25 mph. Chance of rain 30 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Breezy. Isolated showers. Lows 61 to 66. Northeast winds 15 to 20 mph. Chance of rain 20 percent.

Sunday: Mostly sunny in the morning then becoming partly sunny. Breezy. Isolated showers. Highs around 78. Northeast winds 15 to 20 mph. Chance of rain 20 percent.

Kaua’i Mountains

Today: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered light showers in the afternoon. Highs 66 to 74 in the valleys to around 61 above 4000 feet. Northeast winds up to 20 mph. Chance of rain 70 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 55 to 60 in the valleys to around 49 above 4000 feet. Northeast winds 10 to 25 mph. Chance of rain 50 percent.

Sunday: Breezy. Partly sunny with scattered showers. Highs 66 to 74 in the valleys to around 61 above 4000 feet. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

North Kaua’i

Today: Partly sunny with scattered showers in the morning, then mostly sunny with isolated light showers in the afternoon. Highs 71 to 78. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with isolated showers. Lows 57 to 66. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Sunday: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs 71 to 78. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

East Kaua’i

Today: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated light showers in the afternoon. Highs 71 to 77. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 55 to 68. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Sunday: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs 71 to 78. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Cool, stable, and breezy northeasterly trade winds will continue to gradually ease into Sunday, with showers mainly confined to windward and northern slopes. Trade winds will strengthen as high clouds thicken on Monday, and an increase in rainfall is possible late Tuesday into Friday.

Discussion

Cool, stable, and breezy northeasterly trade winds will continue to gradually decline into Sunday. The trades are being driven by a 1031 mb surface high sitting about 1100 miles north of the state, and the winds remain more northeasterly due to the influence of a broad nearly stationary surface low parked about 1500 miles to the northeast. As the high to the north weakens and the low drifts away, winds will ease slightly into Sunday. As dew points within the northeasterly flow hold in the mid to upper 50s, a cool winter-like feel persists, and expect dew points to only slowly climb to the lower 60s by Sunday. While the air mass will continue to be rather dry and capped by a strong low-level inversion, thermal instability in the boundary layer will continue to generate light shower activity across mainly windward and northern slopes, while most leeward areas will be dry.
Easterly trade winds will strengthen Monday and Tuesday as surface high pressure rebuilds to the north. Dew points will recover to more typical seasonal values in the low to mid 60s, and a rather typical pattern of windward and mountain showers will prevail. The ridge aloft will break down as a sharp upper-level trough approaches from the west. Initially, the impact will be a thickening of high clouds as early as Sunday night.
Wet and breezy trade winds are possible by late Tuesday or Wednesday. Broad surface high pressure will persist to the north, likely keeping the gusty trade winds in place. Meanwhile, the mid- to upper-level trough is expected to move closer to the islands. As a result, expect extensive high cloud cover to linger, along with a moistening and potential destabilizing of the air mass. This points towards a wet trade wind pattern with frequent windward showers periodically spilling over to leeward areas.

Aviation

A strong high pressure system far north of the Hawaiian Islands will slowly weaken this weekend. Expect breezy trade winds today with decreasing trends into the moderate to locally breezy range by Sunday. A fairly stable atmosphere will produce passing showers mainly over windward and mountain areas in the overnight to early morning hours. VFR conditions will prevail with only brief MVFR conditions possible in showers mainly over windward airfields.
AIRMET TANGO remains in effect for moderate turbulence below 8000 feet over and immediately south through west of all island mountains. This AIRMET will likely continue through the afternoon today.

Marine

Rough conditions will continue over most Hawaiian waters due to a combination of fresh to strong northeast trades and a mix of north to northeast wind and ground swell moving through. Early morning nearshore buoy observations reflect this with seas hovering a few feet over predicted levels. A combination of the winds and rough seas support the Small Craft Advisory continuing over exposed waters and channels through the weekend.
Guidance shows the winds shifting out of the east early next week and becoming strong. This combined with a large, medium-period northeast swell arriving from a broad gale centered around 1200 nm northeast of the state will support Small Craft Advisory conditions returning for all waters Monday through Tuesday. This northeast swell will likely be large enough to support warning- level surf for east facing shores and advisory-level surf for north facing shores Monday through Tuesday.
A trend back toward a more typical trade wind pattern with seas easing is expected through the second half of next week. Surf along north and west facing shores will trend up as a long-period northwest swell arrives from a broad system emerging out over the far northwest Pacific early next week.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Sunday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Channel, Oahu Windward Waters, Kaiwi Channel, Maui County Windward Waters, Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Windward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov