West Kaua’i

Tonight: Partly cloudy with isolated showers. Lows around 73 near the shore to around 64 above 3000 feet. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Thursday: Mostly sunny with scattered showers in the morning, then partly sunny with isolated showers in the afternoon. Highs 84 to 90 near the shore to around 75 above 3000 feet. Northeast winds 10 to 15 mph. Chance of rain 40 percent.

Thursday Night: Mostly cloudy with isolated showers. Lows around 73 near the shore to around 64 above 3000 feet. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

South Kaua’i

Tonight: Breezy. Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 69 to 76. Northeast winds 10 to 25 mph. Chance of rain 40 percent.

Thursday: Breezy. Partly sunny with scattered showers. Highs 79 to 89. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Thursday Night: Breezy. Mostly cloudy with scattered showers. Lows 69 to 76. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Kaua’i Mountains

Tonight: Windy. Mostly cloudy with scattered showers. Lows 66 to 71 in the valleys to around 61 above 4000 feet. Northeast winds 10 to 30 mph. Chance of rain 50 percent.

Thursday: Breezy. Mostly cloudy with scattered showers. Highs 72 to 79 in the valleys to around 66 above 4000 feet. Northeast winds 10 to 25 mph. Chance of rain 50 percent.

Thursday Night: Windy. Mostly cloudy with scattered showers. Lows around 68 in the valleys to around 61 above 4000 feet. Northeast winds 10 to 30 mph. Chance of rain 50 percent.

North Kaua’i

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 64 to 75. East winds 10 to 20 mph. Chance of rain 50 percent.

Thursday: Breezy. Partly sunny with scattered showers. Highs 69 to 85. East winds 10 to 20 mph. Chance of rain 50 percent.

Thursday Night: Breezy. Mostly cloudy with scattered showers. Lows 64 to 74. East winds 10 to 20 mph. Chance of rain 50 percent.

East Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows 66 to 76. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Thursday: Partly sunny with scattered showers. Highs 76 to 84. East winds 10 to 15 mph. Chance of rain 50 percent.

Thursday Night: Mostly cloudy with scattered showers. Lows 66 to 75. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Breezy trade winds will persist through the next several days as surface high pressure holds north of the state. Pockets of moisture moving through with the trades will focus rainfall over windward and mauka areas with showers briefly passing over leeward areas. A tropical disturbance well to the south will enhance showers on windward Big Island, Maui, and perhaps as far north as Oahu Friday into Saturday.

Discussion

After numerous showers in windward, mauka, and some leeward areas of the smaller islands this morning, coverage has decreased this afternoon and are focused mostly in windward areas. Little change is expected tonight through at least Thursday. A ridge of high pressure north of the state is driving breezy trades across the island chain, which will continue. Additional pockets of moisture will focus showers over windward and mauka areas, particularly during the overnight and early morning hours.
An area of showers and thunderstorms is gradually becoming better organized well southeast of the state. There remains a high chance (70 percent) of this activity gradually developing into a tropical cyclone within a few days. The ridge to our north will steer this system westward and keep direct impacts well to the south. However, a rich plume of moisture will pass through southern parts of the state characterized by anomalously high pwats around 2.25 inches. The last several model runs have shown a consistent trend with bringing this deep moisture farther north. What looked like the Big Island being grazed with this moisture 24 hours ago now looks like at least the Big Island and Maui, perhaps as far north as Oahu. In addition, with surface high pressure settling southeast toward the state while the potential tropical system passes to the south, trades may strengthen further Friday into Saturday. Timing consistency is improving between the GFS and the ECMWF with the deep moisture arriving by late Friday morning and exiting to the west sometime Saturday morning. PoPs and QPF have been increased during this period for windward areas, but given the trades and moisture content of the airmass, some of these showers may spill into leeward areas as well. Locally heavy rainfall will be possible.
After the passage of that system, much drier air and lower inversion heights will filter in from the east northeast Sunday into next week. Shower coverage will decrease, but a few may remain possible in windward locations each day.

Aviation

Breezy trades expected for next few days. Low cigs and SHRA will continue over windward and mauka locations with some spillover into leeward areas at times. MVFR conds in SHRA, otherwise VFR prevails.
AIRMET Sierra has been cancelled for all areas as conditions have improved.
AIRMET Tango remains in effect for mod turb lee of terrain and should remain in effect for next few days. AIRMET for mod turb FL250-300 across the islands has been cancelled as conditions have improved.

Marine

Fresh to locally strong trade winds with responding high seas will persist the next several days. This is a result of a tight north to south pressure gradient across the waters from higher pressure north of the state in relation to lower equatorial pressure. Due to this combination of strong trades and responding elevated seas, a Small Craft Advisory remains in effect for all marine zones for the foreseeable future. An area of disturbed weather far southeast of the islands is being monitored for the high likelihood of tropical cyclone development. This disturbance, or whatever it evolves into, will travel south of the Hawaiian Islands through early next week.
A moderate size, long period northwest swell will begin arriving early Thursday morning and will likely be detected at the far northwest offshore buoys this evening. As this swell fills in around the island chain tomorrow, it will increase north and west- facing shore surf heights to advisory levels. A High Surf Advisory will be in effect from 6 AM HST Thursday morning through 6 AM HST Friday morning for the smaller islands. A reinforcing moderate size, medium period northwest swell will arrive Saturday and likely prolong elevated moderate size north and west surf through the weekend.
A compact fetch of gales passing east of New Zealand late last week created swell that should reach the local waters in a couple of days. This very slight bump in south southwest swell may produce near to slightly above average south-facing shore surf this weekend. Moderate to strong trade winds will ensure rough and choppy conditions along east-facing shores well into next week.

Fire weather

Persistent rainfall will likely limited the widespread availability of receptive fuels. Breezy winds will continue during the next several days, generating moderate fire weather conditions. The inversion near Big Island will range from 6000 to 8000 ft over the next few days.

HFO Watches/Warnings/Advisories

High Surf Advisory from 6 AM Thursday to 6 AM HST Friday for Kauai North, Kauai Southwest, Maui Central Valley North, Maui Windward West, Molokai North, Molokai West, Molokai Windward, Niihau, Oahu North Shore, Waianae Coast, Windward Haleakala.
Small Craft Advisory until 6 AM HST Friday for Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters, Big Island Windward Waters, Kaiwi Channel, Kauai Channel, Kauai Leeward Waters, Kauai Northwest Waters, Kauai Windward Waters, Maalaea Bay, Maui County Leeward Waters, Maui County Windward Waters, Oahu Leeward Waters, Oahu Windward Waters, Pailolo Channel.

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Data Courtesy of NOAA.gov