Photo Credit: Brendan Stephen

West Kaua’i

Today: Sunny. Highs around 81 near the shore to around 70 above 3000 feet. Northeast winds up to 10 mph shifting to the southeast in the afternoon.

Tonight: Clear. Lows 64 to 69 near the shore to around 54 above 3000 feet. Light winds becoming northeast up to 10 mph after midnight.

Friday: Sunny and haze. Highs 79 to 84 near the shore to around 71 above 3000 feet. East winds up to 10 mph.

South Kaua’i

Today: Sunny. Highs 77 to 82. East winds 10 to 15 mph.

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

Friday: Sunny and haze. Highs 79 to 84. Light winds becoming southeast around 10 mph in the afternoon.

Kaua’i Mountains

Today: Sunny. Highs 72 to 77 in the valleys to around 63 above 4000 feet. Southeast winds up to 10 mph.

Tonight: Partly cloudy. Lows 55 to 63 in the valleys to around 53 above 4000 feet. Light winds.

Friday: Mostly sunny. Haze. Highs 72 to 78 in the valleys to around 65 above 4000 feet. Light winds.

North Kaua’i

Today: Mostly sunny. Highs 72 to 80. Southeast winds up to 15 mph.

Tonight: Mostly clear. Lows 58 to 66. Southeast winds up to 10 mph.

Friday: Sunny and haze. Highs 73 to 82. Southeast winds up to 10 mph.

East Kaua’i

Today: Partly sunny in the morning then becoming sunny. Highs 70 to 80. East winds up to 10 mph.

Tonight: Partly cloudy. Lows 57 to 68. Light winds.

Friday: Mostly sunny. Haze. Highs 72 to 82. South winds up to 10 mph shifting to the southeast around 10 mph in the afternoon.

Detailed Forecast

Synopsis

Moderate trades will turn southeasterly tonight giving rise to a land and sea breeze pattern over the smaller islands that will continue through Saturday. No rain is expected during this time. A brief return to a trade wind shower pattern is possible by Saturday night.

Discussion

With the progression of the nocturnal period, cloud free skies from last evening have given way to a fairly high coverage of stable and flat cloud cover over the waters and adjacent windward zones. This thin cloud cover will burn off with the onset of diurnal heating but will regenerate each night as a very shallow inversion between 2.5 and 4kft makes the most of limited boundary layer moisture flux. A deep anticyclone centered directly over the islands in the mid-levels and positioned immediately north of the islands at the surface will work through the area during the next 24 hours. Deep layer subsidence will further increase during this time bringing even greater stability while dewpoints hover in the 50s. In this environment, moderate trades will struggle to produce anything more than patchy clouds over the terrain.
As the aforementioned high shifts east, trades will veer to southeasterly tonight through Saturday resulting in blocked flow and an emerging land and sea breeze pattern over the smaller islands. Interior clouds each afternoon will give way to clear skies as land breezes develop overnight. Meanwhile, a modest increase in low-level moisture and subsequent weakening of the inversion over the eastern end of the state will accompany the transition to southeasterly background flow. Shower activity will nonetheless remain quite sparse through Saturday except, perhaps, over Windward Maui where enhanced southeast flow bending around the Hamakua Coast of the Big Island may be sufficient to generate a locally greater coverage of showers.
Global model consensus indicates a return to more typical trade wind shower pattern late Saturday through at least Sunday as high pressure refocuses further north during the latter half of the weekend. Rainfall amounts will remain light during this period as the lingering deep layer of dry and stable air confines meaningful moisture return to a relatively shallow layer in the lowest levels.

Aviation

A surface high pressure system located north of the islands will move east to a position northeast of the area by tonight. This will produce moderate easterly trade winds today, followed by weakening east-southeast flow by this evening. The atmosphere is very stable and dry, so mainly stratocumulus clouds are expected to move over windward sections. No significant precipitation is in the forecast through early Friday morning. Therefore, expect VFR conditions to prevail across the state during the next 24 hours.
No AIRMETs are currently in effect, and none are anticipated today.

Marine

An extra-large NW (330 degrees) swell propagating through island waters has been slow to diminish overnight. Observations from NDBC buoys 51001/51101 NW of Kauai indicate little drop in significant wave height, while the predominant wave period has dropped to near 15 seconds. Very large surf along exposed shorelines will persist into tonight, and a High Surf Warning (HSW) has been extended through early Friday for shorelines most exposed to the swell. Some other shores less exposed to the swell are the subject of a High Surf Advisory (HSA), with additional details contained in the latest Coastal Hazard Message (CFWHFO), Marine Weather Statement (MWSHFO), and Surf Zone Forecast (SRFHFO). The swell will gradually diminish (but remain above HSA levels on some shores) Friday as the primary swell direction veers toward the N (350 degrees).
Another powerful (but smaller) very long-period NW (310 degrees) swell is expected Saturday through Monday, with peak surf heights approaching HSW values. After this long-lived swell eases, surf heights early next week look to remain below HSA heights along all shores as moderate-sized NW swells arrive, with a small S swell possible this weekend.
A Small Craft Advisory posted for all zones (except Maalaea bay) has been extended through tonight, as combined seas will be slow to diminish below 10 feet, with near shore buoys showing seas currently ranging from 10 to 17 feet. Combined seas should lower below 10 feet by Friday morning, but will approach 10 feet again over the weekend.
An eastward-moving and relatively weak (1021 mb) surface high is centered about 300 nm NNE of Kauai, producing moderate to locally strong ENE trade winds. The high will move E through tonight, and light to moderate (locally strong in the channels) winds will veer to the E and SE. The high will then remain relatively stationary about 600 nm ENE of the islands into early next week. The associated ridge will be just N of Kauai through this period, generally supporting light to moderate E to SE winds that may get a little stronger when the ridge moves N briefly on Sunday.

HFO Watches/Warnings/Advisories

High Surf Warning until 6 AM HST Friday for Niihau, Kauai Leeward, Waianae Coast, Oahu North Shore, Maui Windward West, Kona, Kohala, Kauai North, Molokai Windward, Molokai North, Molokai West, Maui Central Valley North, Windward Haleakala.
High Surf Advisory until 6 AM HST Friday for Maui Leeward West, Lanai Leeward, Big Island East, Big Island North.
Small Craft Advisory until 6 AM HST Friday for all Hawaiian waters except Maalaea Bay,

Data Courtesy of NOAA.gov