West Kaua’i

Tonight: Breezy. Partly cloudy with isolated showers. Lows around 72 near the shore to around 63 above 3000 feet. Northeast winds up to 20 mph. Chance of rain 20 percent.

Sunday: Breezy. Mostly sunny with isolated showers. Highs 84 to 91 near the shore to around 76 above 3000 feet. Northeast winds up to 20 mph. Chance of rain 20 percent.

Sunday Night: Partly cloudy with isolated showers. Lows around 72 near the shore to around 63 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

South Kaua’i

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 71 to 76. Northeast winds 15 to 25 mph. Chance of rain 50 percent.

Sunday: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs 79 to 89. Northeast winds 15 to 25 mph. Chance of rain 50 percent.

Sunday Night: Partly cloudy. Breezy. Isolated showers in the evening, then scattered showers after midnight. Lows 70 to 76. Northeast winds 10 to 20 mph. Chance of rain 40 percent.

Kaua’i Mountains

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows around 68 in the valleys to around 60 above 4000 feet. East winds up to 20 mph. Chance of rain 70 percent.

Sunday: Breezy. Partly sunny with scattered showers. Highs 73 to 81 in the valleys to around 66 above 4000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Sunday Night: Breezy. Mostly cloudy with scattered showers. Lows around 67 in the valleys to around 60 above 4000 feet. East winds up to 20 mph. Chance of rain 50 percent.

North Kaua’i

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

Sunday: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs 71 to 86. East winds up to 20 mph. Chance of rain 50 percent.

Sunday Night: Breezy. Partly cloudy with scattered showers. Lows 64 to 74. East winds up to 20 mph. Chance of rain 40 percent.

East Kaua’i

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 67 to 75. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Sunday: Breezy. Partly sunny with scattered showers. Highs 76 to 85. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Sunday Night: Mostly cloudy with scattered showers. Lows 67 to 75. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Breezy trade winds will usher in windward clouds and showers through Monday. Hurricane Fausto is expected to weaken to a tropical storm as it approaches the islands and will potentially bring heavy rain, winds and surf to portions of the state Tuesday through Wednesday. Trades will fill in Thursday night in the wake of Fausto.

Discussion

Breezy trade winds will usher in windward clouds and showers through Monday. Incoming clouds and showers will focus over windward and mauka areas, mostly occurring during the nighttime and early morning hours. 00Z soundings show a stable environment across the islands with an inversion around 8000 to 9000 feet.
The highlight next week will be the approach of now Hurricane Fausto. Fausto is expected to weaken over the next several days as it tracks west across higher shear and cooler waters, reaching the vicinity of the Hawaiian Islands on Tuesday. Main impacts Tuesday and Wednesday include the possibility of strong winds, flooding rain and east shores surf, and will be dependent upon Fausto's eventual path. Winds could also be mitigated on a more northerly swing of the track, but more impactful if it slides southward, so confidence remains low. For rainfall, mitigating effects will be Fausto's relatively quick west movement limiting how long it will rain will last across each island, but our terrain can capture much of this moisture as it passes through. Meanwhile, swell generated by Fausto has the highest likelihood of occurrence, which will gradually build Sunday night through Monday night.
No time like the present to review your family hurricane preparedness plans, and ensure every household has at least a 14 day supply of food and water available if needed during this years active hurricane season.
A drier and more stable breezy trade wind pattern will fill in across the state from Thursday onward as Fausto continues to journey westward away from the Hawaiian Islands.

Aviation

Breezy trade winds will prevail through the rest of the weekend, before trending down on Sunday night. Afternoon satellite imagery and surface observations show some improvement in low clouds and showers across the western end of the state, but MVFR ceilings and visibilities remain in place across windward sections of the central and eastern islands. Therefore, AIRMET Sierra remains in effect for mountain obscuration for portions of the state. These showers and low clouds are expected to become less widespread through early evening. AIRMET Tango also remains in effect for moderate low-level turbulence downwind of island terrain. This AIRMET will likely continue through at least Sunday.

Marine

Locally strong trades persist through Sunday then gradually back to the NNE and diminish through midweek in response to TC Fausto passing north of the islands. The Small Craft Advisory for the windier waters of the Big Island and Maui County remains in effect through tomorrow.
Plenty of long period energy observed upstream on offshore NDBC buoy 51002 with several hours of moderate sized swell noted in the 16-19 second bands. Nearshore buoys indicate energy spread throughout the wave spectrum but most heavily concentrated in the long period bands in support of borderline High Surf Advisory (HSA) conditions for S facing shores this afternoon. The advisory remains in effect through tonight but may warrant an extension through Sunday conditional on overnight observations.
Locally strong trades support rough surf along E shores slightly above the seasonal average through tonight. As trade wind swell declines with diminishing trades, a long period swell from Hurricane Fausto arrives tonight then builds through Sunday and Monday, peaking late Tuesday into Tuesday night. This swell is forecast to produce advisory-threshold surf along E facing shores as early as Sunday night followed by potential for warning-level surf as it peaks on Tuesday. After a brief lull mid-week, a medium to long period E swell emanating from TC Genevieve in the E Pac will build Thursday night into the weekend.
Surf along N shores remains flat to tiny through the weekend. Some increase is expected as Fausto or its remnants pass over the region Tuesday and Wednesday.

HFO Watches/Warnings/Advisories

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