West Kaua’i

Tonight: Partly cloudy. Isolated showers in the evening. Lows around 73 near the shore to around 63 above 3000 feet. Northeast winds up to 10 mph. Chance of rain 20 percent.

Sunday: Mostly cloudy with scattered showers. Highs 85 to 91 near the shore to around 77 above 3000 feet. Light winds. Chance of rain 50 percent.

Sunday Night: Mostly cloudy with isolated showers in the evening, then partly cloudy after midnight. Lows around 73 near the shore to around 62 above 3000 feet. Light winds. Chance of rain 20 percent.

South Kaua’i

Tonight: Partly cloudy in the evening, then mostly cloudy with isolated showers after midnight. Lows around 74. Northeast winds around 10 mph. Chance of rain 20 percent.

Sunday: Partly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 82 to 90. East winds around 10 mph. Chance of rain 50 percent.

Sunday Night: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 71 to 76. East winds around 10 mph. Chance of rain 20 percent.

Kaua’i Mountains

Tonight: Mostly cloudy with isolated showers. Lows 66 to 71 in the valleys to around 60 above 4000 feet. East winds 10 to 15 mph decreasing to up to 15 mph after midnight. Chance of rain 20 percent.

Sunday: Mostly cloudy with scattered showers. Highs 76 to 84 in the valleys to around 68 above 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Sunday Night: Mostly cloudy with scattered showers in the evening, then partly cloudy after midnight. Lows 65 to 71 in the valleys to around 60 above 4000 feet. East winds around 10 mph shifting to the southeast after midnight. Chance of rain 40 percent.

North Kaua’i

Tonight: Mostly cloudy with isolated showers. Lows 67 to 75. East winds up to 10 mph. Chance of rain 20 percent.

Sunday: Partly sunny with scattered showers. Highs 78 to 88. East winds up to 10 mph. Chance of rain 50 percent.

Sunday Night: Mostly cloudy with scattered showers in the evening, then partly cloudy after midnight. Lows 66 to 74. East winds around 10 mph in the evening becoming light. Chance of rain 30 percent.

East Kaua’i

Tonight: Mostly cloudy with isolated showers. Lows 66 to 77. Northeast winds up to 10 mph. Chance of rain 20 percent.

Sunday: Partly sunny with scattered showers. Highs 75 to 88. East winds up to 10 mph. Chance of rain 50 percent.

Sunday Night: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 65 to 77. East winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Trades will become light over the next couple of days, with rising humidity as Henriette passes by to the north. Moderate trades and more normal humidity levels return by the middle of next week, as Henriette moves northwestward away from the islands.

Discussion

The latest visible satellite imagery is beginning to show a transition from trades to a lighter wind pattern with scattered clouds moving into windward areas, as well as some cloud buildups over leeward/interior areas as the trades begin to weaken this afternoon. Radar imagery shows minimal showers around the islands today, with only a few hundredths of an inch reported over windward areas and the Kona slopes of the Big Island over the past 6 hours.
An area of high pressure remains well northwest of the islands, maintaining moderate trades. However, a disruption in the local pressure gradient will occur later tonight through at least Monday as Tropical Storm Henriette, currently around 450 miles northeast of the Big Island, passes by to the north. Trades will begin to ease and shift out of the southeast tonight, becoming light Sunday through at least Monday with a land-sea breeze pattern dominating. As a result, leeward and interior portions of the islands may experience enhanced shower activity, mainly during the afternoon hours. The next couple of days will also be marked by warm and humid conditions, with dewpoint values projected to reach near 70 in many areas, as the moisture pool associated with Henriette moves through the island chain.
Once Henriette exits the local area to the northwest around Tuesday, the surface high to the northeast will re-exert its influence with moderate trades returning across the islands by late Tuesday. As a result, a more typical summer trade wind weather pattern will become dominant through the remainder of the forecast period.

Aviation

Moderate trades this afternoon will weaken tonight and become light on Sunday. Winds should be light enough for land breezes to develop late tonight and for sea breezes to develop during the day on Sunday. Limited clouds and shower activity is expected tonight with a few light showers across windward and mauka areas. VFR conditions should prevail, but some brief MVFR conditions can't be ruled out with any showers.
An upper level jet moving into our area this evening could bring some light to moderate upper level turbulence between FL300 to 400. AIRMET TANGO may be needed this evening and tonight and we will continue to monitor PIREPs. Otherwise, no AIRMETs are expected.

Marine

Light to moderate trade winds today will become light and variable tonight into Monday morning as Tropical Storm Henriette approaches the eastern border of the far offshore waters on a northwest track, weakening the ridge. Henriette will move far north of the state Monday, allowing a ridge of high pressure to build just north of state. Trades winds will build back briefly to the moderate to fresh range Tuesday into Wednesday. Global models then indicate a trough approaching the area from the east, weakening the ridge and allowing winds to ease to the light to gentle range toward the second half of next week.
The long period south swell that has been bringing above advisory level surf throughout the day is expected to peak tonight near warning levels. A recent spike at the buoys confirms near warning level surf continuing through tonight and into tomorrow morning. If the buoys increase any higher, a high surf warning will be needed. A High Surf Advisory (HSA) remains in effect for all south- facing shores through Sunday night. This swell will gradually fade into next week.
Surf along east facing shores should remain small today due to the lighter trade winds. Tropical Storm Henriette will pass far east of the state tonight, sending a medium period east swell. This swell could briefly increase the east facing shores Sunday before subsiding Monday. Below average east shore surf is expected Tuesday into Wednesday next week. A medium period northeast swell will be possible by Thursday.
Tiny surf along north facing shores will trend down tonight before another tiny pulse arrives tomorrow. Another small northwest swell is expected to arrive Sunday night into 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

Trades will continue to ease over the next couple of days, allowing for the development of a land-sea breeze pattern for much of the state for Sunday and Monday. Dewpoint values are expected to gradually rise through early next week, with many areas nearing dewpoints of 70 degrees. As a result, weather conditions are expected to remain below critical fire weather thresholds. However, remain vigilant when recreating outdoors or when operating equipment that could cause a spark.

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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