West Kaua’i

Tonight: Partly cloudy. Lows around 74 near the shore to around 64 above 3000 feet. Light winds.

Thursday: Mostly sunny. Highs 87 to 93 near the shore to around 80 above 3000 feet. Southeast winds up to 15 mph.

Thursday Night: Partly cloudy. Lows 72 to 77 near the shore to around 64 above 3000 feet. East winds up to 15 mph.

South Kaua’i

Tonight: Partly cloudy. Lows around 75. Northeast winds 10 to 15 mph.

Thursday: Mostly sunny with isolated showers. Highs 83 to 91. East winds 10 to 15 mph. Chance of rain 20 percent.

Thursday Night: Partly cloudy with scattered showers in the evening, then mostly cloudy with isolated showers after midnight. Lows around 75. East winds 10 to 15 mph. Chance of rain 30 percent.

Kaua’i Mountains

Tonight: Mostly cloudy. Lows 67 to 72 in the valleys to around 62 above 4000 feet. Light winds.

Thursday: Mostly sunny with isolated showers. Highs 78 to 87 in the valleys to around 71 above 4000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Thursday Night: Mostly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 67 to 72 in the valleys to around 62 above 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

North Kaua’i

Tonight: Partly cloudy with isolated showers. Lows 68 to 76. East winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Thursday: Mostly sunny with isolated showers. Highs 80 to 89. East winds up to 15 mph. Chance of rain 20 percent.

Thursday Night: Mostly cloudy with isolated showers. Lows 67 to 76. East winds up to 15 mph. Chance of rain 20 percent.

East Kaua’i

Tonight: Mostly cloudy. Lows 67 to 78. Northeast winds up to 10 mph.

Thursday: Partly sunny with scattered showers. Highs 76 to 89. East winds up to 10 mph. Chance of rain 40 percent.

Thursday Night: Mostly cloudy with scattered showers. Lows 67 to 79. East winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Aside from a brief repreive as locally breezy trades return late Thursday through Friday, light winds and muggy conditions prevail into next week.

Discussion

Stable trade winds prevail beneath an inversion residing around 5kft per afternoon soundings. Ridging aloft is providing ample subsidence and maintaining a firm lid on existing shower activity even as PWATs rise toward 1.5″ and dewpoints rise into the 70s areawide. The area will remain within the low-level moisture envelope of tropical remnants passing north of the islands through tomorrow which will lend itself to particularly muggy conditions, especially as dewpoints peak this evening through the first half of tonight. The pressure gradient will also bottom out today as the remnant circulation makes its closest approach to the islands which has led to the emergence of sea breezes over the western slopes of the islands. In these locations, low-level moisture has been sufficient to support persistent scattered showers while mostly rain-free and muggy conditions prevail elsewhere. Similar conditions anticipated on Thursday as trades gradually return through the day, though with comparatively less cloud cover as greater boundary layer moisture lifts away. Moderate to locally breezy trades then make a brief return before Tropical Storm Henriette tracks north of the islands once again reducing the gradient, weakening winds, and bringing a period of muggy conditions for the weekend.

Aviation

A hybrid sea breeze and light to moderate trade wind weather pattern remains in the forecast through tomorrow as the remnants of former Tropical Cyclone Gil continue to drift westward, passing through the region just north of the Hawaiian Islands. Deep tropical moisture will sweep into the islands with this system, with a slight increase in clouds and shower activity expected each afternoon over island mountain and interior sections.
No AIRMETs in effect.

Marine

Trade winds will be weakened and disrupted today with the passage of the remnants of what was once Tropical Cyclone Gil. This weak trough in the proximity of the northern offshore waters will create a period of light and variable breezes during its passage to the west. Trades will strengthen and become more easterly Thursday as this trough moves northwest of Kauai. Locally strong trades over the windier waters surrounding Maui and Big Island will prompt a Small Craft Advisory going in effect 6AM Thursday through 6AM Friday but will most likely need extended. High pressure far northeast of the state will drift to the north over the weekend as Tropical Storm Henriette approaches the region from the east. This may disrupt and weaken the trade flow once again as Henriette takes nearly the same path as Gil. Henriette will be near or north of the far northern Hawaiian offshore waters Sunday.
An extended run of higher south swell will continue through the week. Yesterday's south swell will continue to slowly decline through the day but long period forerunners from the next south swell will build in tonight. This swell will fill in Thursday and peak Friday morning and afternoon. A large reinforcing southern impulse will build in from late Friday through early Saturday. This swell will certainly lift south-facing surf to High Surf Advisory levels…possibly nearing High Surf Warning heights this weekend. This swell will gradually decline early next week.
Eastern exposure surf will be elevated but just under advisory heights through the day in response from a fading captured fetch from former Tropical Cyclone Gil. East swell will decline rapidly late today and Thursday as strengthening trades regenerate near seasonal averages. A captured east swell from Tropical Storm Henriette may arrive this weekend.
A very small northwest swell originating from a former West Pacific typhoon is producing very small surf along north-facing shores. Another tiny northwest swell is scheduled to arrive later today into Thursday and this will prevent north surf from going completely flat.
Peak monthly high tides combined with water levels that are running higher than predicted will lead to minor flooding along the shoreline and in low-lying coastal areas. Coastal flooding is possible around the daily peak tide in the afternoons starting as early as tomorrow and will continue through the weekend.

Fire weather

Minimal fire weather concerns through the forecast period. A brief interlude of slightly drier locally breezy trades late Thursday through Friday is flanked on either side by light winds and muggy conditions with dewpoints in the 70s.

HFO Watches/Warnings/Advisories

None.

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