West Kaua’i

Tonight: Mostly clear. Lows 71 to 76 near the shore to around 63 above 3000 feet. Northeast winds up to 15 mph.

Saturday: Sunny. Highs 85 to 93 near the shore to around 78 above 3000 feet. East winds up to 10 mph shifting to the west in the afternoon.

Saturday Night: Mostly clear. Lows 71 to 76 near the shore to around 63 above 3000 feet. Light winds.

South Kaua’i

Tonight: Mostly clear. Isolated showers in the evening. Lows around 75. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Saturday: Mostly sunny with isolated showers. Highs 84 to 91. East winds 10 to 15 mph. Chance of rain 20 percent.

Saturday Night: Partly cloudy. Isolated showers in the evening. Lows around 74. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Kaua’i Mountains

Tonight: Mostly clear. Isolated showers in the evening. Lows 66 to 71 in the valleys to around 61 above 4000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Saturday: Mostly sunny with isolated showers. Highs 77 to 84 in the valleys to around 69 above 4000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Saturday Night: Partly cloudy. Isolated showers in the evening. Lows 66 to 71 in the valleys to around 60 above 4000 feet. East winds up to 10 mph. Chance of rain 20 percent.

North Kaua’i

Tonight: Mostly clear. Isolated showers in the evening. Lows 67 to 75. Southeast winds up to 15 mph. Chance of rain 20 percent.

Saturday: Mostly sunny with isolated showers. Highs 79 to 88. East winds up to 15 mph. Chance of rain 20 percent.

Saturday Night: Partly cloudy with isolated showers. Lows 66 to 75. East winds up to 10 mph. Chance of rain 20 percent.

East Kaua’i

Tonight: Partly cloudy with isolated showers. Lows 67 to 78. Northeast winds 10 to 15 mph decreasing to up to 10 mph after midnight. Chance of rain 20 percent.

Saturday: Mostly sunny with isolated showers. Highs 76 to 88. East winds around 10 mph. Chance of rain 20 percent.

Saturday Night: Partly cloudy with isolated showers. Lows 65 to 78. Northeast winds up to 10 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Trades diminish by Saturday afternoon resulting in a return of hot and humid conditions as humidity gradually creeps up through the weekend. Moderate trades return by the middle of next week.

Discussion

Locally breezy trades are poised to diminish as quickly as they returned as Henriette passes north of the islands and wipes out the local pressure gradient as early as Saturday afternoon. A land and sea breeze pattern is then favored through at least Monday. Hot and humid conditions gradually return during this time, particularly as low level winds veer to SE in response to developing upper troughing and advect dewpoints in the 70s back into the area early next week. Gradual weakening of the inversion as this occurs will favor increasing odds for afternoon clouds and showers over island interiors, especially by Monday when low- level moisture will be maximized and stability at a relative minimum. Henriette advances north of 30N by Tuesday relinquishing the islands from any of its effects, but a general pattern of mid- level height falls over the central and east Pacific continue well into next week which will generally keep trades moderate as stable weather returns for remainder of the forecast period.

Aviation

Breezy trades continue through the near term then gradually diminish during Saturday as a tropical system passing north of the islands wipes out the local pressure gradient. Limited clouds and showers windward and mauka will produce patchy MVFR but VFR is forecast to prevail.
AIRMET Tango for lee turb will be allowed to expire this evening.

Marine

Moderate to locally strong trade winds will decrease tonight through tomorrow as Post Tropical Cyclone Henriette approaches the area and passes northeast of the offshore waters. Winds will become light and variable tomorrow through Monday morning due to the weakening ridge from Henriette. Then as Henriette exits the region to the north, the ridge will build back in by Monday afternoon through the remainder of next week, increasing trade winds into the fresh range by Tuesday. Global models indicate a trough approaching the area and weakening the winds again by the later part of next week.
Elevated surf heights can be observed today across the south facing shores. This is from a swell that arrived earlier today and will continue supporting advisory level surf before another reinforcing pulse arrives tonight into tomorrow. Surf heights are expected to border on warning levels later tonight and hold through tomorrow. A High Surf Advisory for all south-facing shores is in effect through Sunday night and could be upgraded to a warning if the swell comes in larger. The swell will gradually fade through next week.
Surf for east facing shores should remain choppy tonight and should decrease slightly tomorrow as trade winds decrease. A medium period east swell from Tropical Storm Henriette may arrive around Sunday and briefly increase the east facing shores.
A small, medium northwest swell passing through today and tomorrow will keep north shore surf from going completely flat. Another tiny northwest swell is expected to arrive by Monday.
Peak afternoon high tides, combined with elevated water levels running about a half a foot higher than predicted and a large south swell, will lead to minor flooding along many south-facing shorelines and low lying coastal areas through Sunday afternoon.

Fire weather

Breezy trades gradually diminish through Saturday with light winds then continuing into next week. After bottoming out in the upper 60s today, dewpoints will gradually rise back into the 70s for Sunday and Monday. Minimal fire weather concerns during this time.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 AM HST Monday for Niihau, Kauai Leeward, Waianae Coast, Kahoolawe, Maui Leeward West, Kona, Kohala, Kauai South, East Honolulu, Honolulu Metro, Ewa Plain, Molokai Southeast, Molokai Leeward South, Lanai Leeward, Lanai South, Maui Central Valley South, South Maui/Upcountry, South Haleakala, Big Island South, Big Island Southeast.

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