West Kaua’i

Tonight: Partly cloudy. Lows 71 to 76 near the shore to around 63 above 3000 feet. East winds 10 to 15 mph.

Sunday: Mostly sunny. A 20 percent chance of showers in the morning. Highs 87 to 92 near the shore to around 78 above 3000 feet. East winds 10 to 15 mph.

Sunday Night: Partly cloudy. A 20 percent chance of showers after midnight. Lows 71 to 76 near the shore to around 63 above 3000 feet. East winds 10 to 15 mph.

South Kaua’i

Tonight: Breezy. Partly cloudy with slight chance of showers in the evening, then mostly cloudy with chance of showers after midnight. Lows around 75. Northeast winds 15 to 20 mph. Chance of rain 40 percent.

Sunday: Breezy. Partly sunny with chance of showers in the morning, then mostly sunny with slight chance of showers in the afternoon. Highs 82 to 90. Northeast winds 15 to 20 mph. Chance of rain 50 percent.

Sunday Night: Partly cloudy with slight chance of showers in the evening, then mostly cloudy with chance of showers after midnight. Lows around 75. Northeast winds around 15 mph. Chance of rain 50 percent.

Kaua’i Mountains

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Breezy. A 50 percent chance of showers. Lows 66 to 71 in the valleys to around 61 above 4000 feet. East winds 15 to 20 mph.

Sunday: Partly sunny. Breezy. Showers likely in the morning, then chance of showers in the afternoon. Highs 76 to 85 in the valleys to around 68 above 4000 feet. East winds 15 to 20 mph. Chance of rain 70 percent.

Sunday Night: Mostly cloudy with a 50 percent chance of showers. Lows 66 to 71 in the valleys to around 61 above 4000 feet. East winds 10 to 15 mph.

North Kaua’i

Tonight: Partly cloudy with slight chance of showers in the evening, then mostly cloudy with chance of showers after midnight. Lows 66 to 75. East winds 10 to 15 mph. Chance of rain 40 percent.

Sunday: Partly sunny with a 50 percent chance of showers. Highs 78 to 88. East winds 10 to 15 mph.

Sunday Night: Partly cloudy. Slight chance of showers in the evening, then chance of showers after midnight. Lows 67 to 75. East winds 10 to 15 mph. Chance of rain 40 percent.

East Kaua’i

Tonight: Partly cloudy with slight chance of showers in the evening, then mostly cloudy with chance of showers after midnight. Lows 67 to 78. Northeast winds around 15 mph. Chance of rain 50 percent.

Sunday: Partly sunny with a 50 percent chance of showers. Highs 75 to 87. Northeast winds 10 to 15 mph.

Sunday Night: Mostly cloudy with a 50 percent chance of showers. Lows 66 to 78. East winds 10 to 15 mph.

Detailed Forecast

Synopsis

Breezy to locally windy trades and rather dry and stable conditions will continue through tonight. Clouds and light showers being carried in on the trade wind flow will remain focused over windward and mauka areas, while most leeward areas will remain dry over the next several days. Trade winds will gradually ease Sunday through Tuesday and will likely be disrupted Wednesday into parts of Thursday as the remnants of Gil passes to our north. An increase of showers are possible Wednesday and Thursday.

Discussion

A 1030 mb high centered far north of the state is driving windy and dry conditions across the state this afternoon. Afternoon soundings from Lihue and Hilo show the trade wind inversion between roughly 5,000 to 6,500 feet. For rest of this afternoon and tonight, we are expecting the inversion to lower slightly with an increase of 850 mb winds. This should translate to surface winds strengthening especially in areas downwind of terrain. With gusty winds expected through tonight, the Wind Advisory for parts of Maui County and the Big Island has been expanded in area and extended through 6 am Sunday. 850 mb winds should decrease on Sunday, which should decrease the gust factor although gusty winds will still persist throughout the day Sunday. Shallow pockets of moisture will be carried in with the windy trades and could produce some light rainfall accumulation mainly across windward slopes.
Trade winds will gradually decline Sunday into Tuesday as the high drifts eastward and the local pressure gradient slowly relaxes. By Monday, Trade winds should return to our typical breezy levels with mostly dry conditions continuing to persist across the state.
Trades will likely become disrupted Wednesday into parts of Thursday, as the remnants of Gil passes to our north. The latest National Hurricane Center forecast remains on track with Tropical Storm Gil weakening to a remnant low by Monday. Although there are some uncertainty, latest model guidance continue to show the main blob of moisture passing north of Hawaii. If this forecast holds, the threat for heavy rain will remain low with mainly scattered showers in the light to moderate intensity. With the trades briefly disrupted and higher dewpoints (possibly low 70s), warm and humid conditions are also expected during this time.

Aviation

High pressure far north and northeast of the islands combined with a trough passing well to the southwest, will maintain breezy to windy trade winds through this evening. As the pressure gradient weakens tomorrow, winds will trend slightly lighter than today, but should remain breezy to locally windy. 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 low level turbulence over and immediately S through W of the island mountains due to strong trade winds and gusts. This AIRMET will likely be needed through tomorrow.

Marine

High pressure will remain far north of the state for the rest of the weekend, which will support fresh to locally strong trades across the coastal waters. Based on the latest ASCAT pass and hi- res guidance, the Small Craft Advisory (SCA) has been expanded in area to cover all coastal waters through tonight. The SCA will then remain in effect for the typically windier channels and waters of Maui County and the Big Island through Sunday as trades begin to ease. Trades will continue to weaken through the first half of next week as the aforementioned high drifts further east.
Surf observations from south facing shores across the state, and trends in the Barber's Point and Lanai nearshore buoys today, indicate that the current south swell is continuing to gradually decline. However, another moderate, long period, south swell is expected to arrive late Sunday into Monday, which could boost surf along south facing shores back up to near advisory levels early next week. This will be followed by yet another long period south swell arriving during the second half of the week.
East shore surf will remain elevated and choppy through most of the day on Sunday due to locally strong trade winds. Surf along east facing shores will begin to lower slightly as trades slowly ease from late Sunday through the rest of the week.
Nearly flat conditions will prevail along north facing shores through early Sunday morning. A small, long period northwest swell originating from Typhoon Krosa in the western Pacific will bring a small bump up in surf along north facing shores Sunday into early next week. Another boost is possible Wednesday night into Thursday.

Fire weather

A gusty, stable, and rather dry trade wind flow will remain in place through Sunday, producing critical fire weather conditions, with winds of 20 mph or more and daytime relative humidity as low as 35 to 45 percent. A strong inversion is in place between 5,000 to 6,500 feet, which will ensure that higher elevations of the Big Island and portions of Haleakala on Maui experience very low relative humidity. This inversion is expected to slightly lower tonight into Sunday, which could increase the gusty winds downwind of terrain especially this afternoon through early tonight. Winds will slowly ease Sunday into Tuesday, which should cause winds to fall below Red Flag thresholds by Monday. Although the winds decrease, dry conditions will continue to persist through Tuesday. An increase of humidity and shower activity will be possible towards the middle of the week as the remnants of Gil passes to our north.

HFO Watches/Warnings/Advisories

Red Flag Warning until 6 PM HST Sunday 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.
Wind Advisory until 6 AM HST Sunday for Lanai Mauka, Maui Windward West, Maui Leeward West, Kohala, Molokai Southeast, Molokai North, Molokai West, Molokai Leeward South, Lanai Windward, Lanai Leeward, Maui Central Valley North, Maui Central Valley South, South Haleakala, Big Island Southeast, Big Island North.
Small Craft Advisory until 6 AM HST Sunday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Maui County Leeward 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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