West Kaua’i

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

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy after midnight. Haze after midnight. Lows 70 to 75 near the shore to around 63 above 3000 feet. Light winds. Chance of rain 40 percent.

Monday: Haze in the morning. Mostly sunny with isolated showers. Highs 86 to 92 near the shore to around 78 above 3000 feet. Southeast winds up to 10 mph. Chance of rain 20 percent.

South Kaua’i

Today: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 82 to 90. East winds up to 10 mph. Chance of rain 40 percent.

Tonight: Partly cloudy with isolated showers. Haze after midnight. Lows around 74. East winds up to 10 mph. Chance of rain 20 percent.

Monday: Haze in the morning. Mostly sunny with isolated showers. Highs 84 to 91. Southeast winds around 10 mph. Chance of rain 20 percent.

Kaua’i Mountains

Today: Mostly sunny with scattered showers in the morning, then mostly cloudy with numerous showers in the afternoon. Highs 76 to 83 in the valleys to around 68 above 4000 feet. Light winds. Chance of rain 70 percent.

Tonight: Partly cloudy. Isolated showers in the evening. Haze after midnight. Lows 65 to 70 in the valleys to around 60 above 4000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Monday: Haze in the morning. Sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 76 to 85 in the valleys to around 69 above 4000 feet. Southeast winds up to 10 mph. Chance of rain 30 percent.

North Kaua’i

Today: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs 77 to 87. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy. Scattered showers in the evening. Haze after midnight. Lows 66 to 74. East winds up to 10 mph in the evening becoming light. Chance of rain 30 percent.

Monday: Mostly sunny. Haze in the morning. Isolated showers in the afternoon. Highs 79 to 88. Light winds. Chance of rain 20 percent.

East Kaua’i

Today: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 75 to 88. East winds up to 10 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with isolated showers. Haze after midnight. Lows 65 to 77. Light winds. Chance of rain 20 percent.

Monday: Mostly sunny. Haze in the morning. Isolated showers in the afternoon. Highs 77 to 90. Southeast winds up to 10 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Winds will remain light over the next couple of days, instilling a land-sea breeze pattern with rising humidity as Henriette passes to the north of the state. By late Wednesday, a low-level trough propagates into the vicinity of the islands, increasing the probability of clouds and enhanced shower activity for windward and mountain areas. Trades return thereafter, allowing humidity levels to return to normal for the remainder of the forecast period.

Discussion

An area of high pressure remains well northeast of the state, while Henriette propagates northwestward, maintaining distance away from the islands. As Henriette passes through the region, trades will be disrupted, resulting in a light and variable pattern through Monday afternoon. In the absence of local scale winds, island heating will develop sea breezes each day, and overnight cooling will drive downsloping land breezes each night. During the day, sea breezes will enhance leeward and interior region shower activity, while land breezes overnight will clear the night skies, limiting showers. Additionally, hot and humid conditions can be expected across most locations as dewpoint values are progged to reach and even exceed 70 in some locations, given the influx of excess moisture associated with Henriette while passing in the vicinity of the islands.
Latest projection on the tracking of Henriette has it well north of the islands late Monday into early Tuesday, releasing its influence on the islands, and allowing trades to reestablish across the state. The aforementioned area of high pressure will then regain dominance over the region briefly.
By late Wednesday, latest model guidance depicts a low-level trough that propagates westward into the state. Temperature inversions across much of the state increase to near 8,000 feet during this time, increasing cloud cover and shower trends across the state, favoring windward and mountain areas of all islands. This quick-moving trough continues westward and exits on the west side of the islands by late Friday.
Thereafter, as the weekend approaches, trades strengthen back to moderate to locally breezy and a more typical summer-like trade wind weather pattern will once again prevail.

Aviation

Light and variable winds prevail, with enhanced shower activity across leeward and interior regions across all islands, and a few light showers across windward and mountain areas. VFR conditions are expected to prevail, however, brief MVFR conditions cannot be ruled out with showers.
There are no AIRMETs in effect at this time.

Marine

Light and variable winds will continue through Monday as Tropical Storm Henriette continues on a northwestward path, passing north of the Hawaiian Islands. A ridge will build into the region with a return to moderate trade winds as Henriette departs the pattern. Trades winds will briefly strengthen into moderate to fresh range from Tuesday into Wednesday. Global models then show a trough moving westward through the region, weakening the ridge and allowing winds to ease into the light to gentle range through Thursday. Moderate to locally strong trades blow across the region from Friday through next weekend.
The long period south swell will hold at high end High Surf Advisory (HSA) levels, just below warning thresholds this morning. Surf heights will slowly decline through tonight. However, surf heights will likely remain above HSA thresholds into Monday. Therefore the current HSA was extended in time through Monday afternoon for the south facing shores of all islands. After this current south swell diminishes from Tuesday into Wednesday, we expect only small long and medium period background pulses along south facing shores into next weekend.
Surf along east facing shores will increase as Tropical Storm Henriette passes northeast of the state today, sending a medium period east swell into the islands. This swell will decrease rather quickly on Monday with smaller east shore surf expected from Tuesday into Wednesday. A medium period northeast swell will be possible by Thursday.
Tiny surf along north facing shores will continue with just small energy pulses keeping north shore surf above flat levels this week.
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 this afternoon.

Fire weather

Winds will remain light and variable over the next couple of days, allowing for the development of a land-sea breeze pattern for much of the state through Monday. Dewpoint values are expected to gradually rise through early next week, with many areas nearing or even exceeding 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 PM 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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