West Kaua’i

Tonight: Mostly clear with isolated showers. Lows 71 to 76 near the shore to around 64 above 3000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Saturday: Sunny. Isolated showers in the morning. Highs 87 to 92 near the shore to around 78 above 3000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Saturday Night: Mostly clear. Lows 71 to 76 near the shore to around 63 above 3000 feet. East winds 10 to 15 mph.

South Kaua’i

Tonight: Partly cloudy with scattered showers. Lows around 75. Northeast winds around 15 mph. Chance of rain 50 percent.

Saturday: Mostly sunny. Breezy. Isolated showers in the morning. Highs 82 to 90. East winds 15 to 20 mph. Chance of rain 20 percent.

Saturday Night: Partly cloudy. Breezy. Isolated showers after midnight. Lows around 75. Northeast winds 15 to 20 mph. Chance of rain 20 percent.

Kaua’i Mountains

Tonight: Breezy. Mostly cloudy with numerous showers. Lows 66 to 71 in the valleys to around 61 above 4000 feet. East winds 15 to 20 mph. Chance of rain 70 percent.

Saturday: Breezy. Partly sunny with numerous showers in the morning, then mostly sunny with scattered showers in the afternoon. Highs 75 to 85 in the valleys to around 68 above 4000 feet. East winds 15 to 20 mph. Chance of rain 70 percent.

Saturday Night: Partly cloudy in the evening then becoming mostly cloudy. Breezy. Scattered showers. Lows 66 to 71 in the valleys to around 61 above 4000 feet. East winds 15 to 20 mph. Chance of rain 50 percent.

North Kaua’i

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows 66 to 75. East winds 10 to 15 mph. Chance of rain 50 percent.

Saturday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 78 to 88. East winds 10 to 15 mph. Chance of rain 50 percent.

Saturday Night: Partly cloudy with isolated showers. Lows 66 to 75. East winds 10 to 15 mph. Chance of rain 20 percent.

East Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows 67 to 78. East winds around 15 mph. Chance of rain 50 percent.

Saturday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 74 to 87. East winds around 15 mph. Chance of rain 50 percent.

Saturday Night: Partly cloudy with isolated showers. Lows 67 to 78. Northeast winds around 15 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Breezy to locally windy trades and rather dry and stable conditions will continue through Saturday. Clouds and light showers will be focused over windward and mauka areas, while most leeward areas remain dry. Stable trade winds will gradually ease Sunday through Tuesday and may become disrupted Wednesday or Thursday.

Discussion

A gusty, stable, and rather dry trade wind flow will persist through Saturday. The trades will remain breezy to locally windy as the local pressure gradient remains tight, due to surface high pressure drifting eastward about 1,000 miles north of the state and a trough moving westward in the deep tropics south of the islands. High pressure aloft will maintain an inversion between 5,000 to 6,000 feet, and the resulting stability will continue to produce localized strong winds near terrain across the Kohala Districts of the Big Island and the central valley of Maui, where the Wind Advisory has been extended through Saturday afternoon. Shallow pockets of moisture being carried in on the trade wind flow will continue to bring light rainfall accumulation mainly to windward slopes, with leeward areas remaining dry.
Trade winds will gradually decline Sunday into Tuesday as the high drifts eastward and the local pressure gradient slowly relaxes. The stable pattern of mainly windward and mauka showers, essentially typical August rainfall, should persist as little organized moisture is depicted in the guidance.
Trades will likely become disrupted Wednesday or Thursday, though there is uncertainty in the details. The latest National Hurricane Center forecast depicts current east Pacific Tropical Storm Gil weakening to a remnant low well east of Hawaii early next week, and the GFS and ECMWF show a remnant circulation passing north or near the state as early as Wednesday but potentially Thursday. Disrupted trades is the most likely scenario, but it's too early to know if there will be any significant chance for enhanced rainfall.

Aviation

High pressure far north and northeast of the islands, combined with a low pressure system to the southwest, will maintain breezy to windy trade winds into the weekend. VFR conditions are expected to prevail, however some passing showers could bring brief MVFR conditions mainly to windward and mountain areas, especially overnight and in the early morning hours.
AIRMET Tango is in effect for moderate with isolated severe turbulence over and immediately S through W of the island mountains due to strong trade winds and gusts.

Marine

High pressure will remain far north of the state this weekend and help generate fresh to locally strong trades across the local waters. A Small Craft Advisory (SCA) has been extended through tomorrow for most marine zones surrounding Maui and the Big Island, then limited to the typical windier zones through Sunday. Trades then begin to weaken by early next week as the aforementioned high drifts further east.
The current south swell has been holding steady all day at the buoys bringing a steady supply of advisory level surf to south facing shores. As such, a High Surf Advisory remains in effect for the south facing shores of all islands through 6 AM HST Saturday morning. This south swell will gradually decline tonight through the weekend, then another south swell should arrive late Sunday into Monday and help build surf heights to near advisory levels once again early next week.
East shore surf will remain elevated and choppy due to locally strong trade winds through this weekend. This will be followed by a decline early next week as trades weaken.
Nearly flat summer conditions along north facing shores may be interrupted late this weekend by a small long period northwest swell from Typhoon Krosa, currently in the western Pacific.

HFO Watches/Warnings/Advisories

Red Flag Warning until 6 PM HST Saturday for Niihau, Kauai South, Kauai Southwest, East Honolulu, Honolulu Metro, Ewa Plain, Waianae Coast, Oahu North Shore, Central Oahu, Waianae Mountains, Molokai North, Molokai West, Molokai Leeward South, Lanai Windward, Lanai Leeward, Lanai South, Lanai Mauka, Kahoolawe, Maui Leeward West, Maui Central Valley North, Maui Central Valley South, South Maui/Upcountry, South Haleakala, Big Island South, Big Island Southeast, Kohala, Big Island Interior.
High Surf Advisory until 6 AM HST Saturday for Niihau, Kauai Leeward, Waianae Coast, Kahoolawe, Maui Leeward West, Kona, Kauai South, East Honolulu, Honolulu Metro, Ewa Plain, Molokai Southeast, Molokai Leeward South, Lanai Leeward, Lanai South, Maui Central Valley South, Kipahulu, South Maui/Upcountry, South Haleakala, Big Island South, Big Island Southeast.
Wind Advisory until 6 PM HST Saturday for Kohala, Maui Central Valley North, Maui Central Valley South, Big Island North.
Small Craft Advisory until 6 PM HST Saturday for Kaiwi Channel, Maui County Windward Waters, Big Island Windward Waters.
Small Craft Advisory until 6 PM HST Sunday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

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