West Kaua’i

Rest Of Today: Mostly sunny late in the morning then becoming partly sunny. Isolated showers. Highs 85 to 92 near the shore to around 77 above 3000 feet. Southwest winds up to 10 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Isolated showers in the evening. Lows around 73 near the shore to around 61 above 3000 feet. Light winds. Chance of rain 20 percent.

Monday: Mostly sunny with isolated showers. Highs 86 to 91 near the shore to around 77 above 3000 feet. East winds up to 15 mph shifting to the south in the afternoon. Chance of rain 20 percent.

South Kaua’i

Rest Of Today: Mostly sunny with isolated showers. Highs 83 to 91. East winds around 10 mph shifting to the south in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows around 74. Light winds. Chance of rain 20 percent.

Monday: Mostly sunny with isolated showers. Highs 83 to 91. Northeast winds up to 10 mph shifting to the east in the afternoon. Chance of rain 20 percent.

Kaua’i Mountains

Rest Of Today: Partly sunny with scattered showers. Highs 78 to 85 in the valleys to around 68 above 4000 feet. Light winds. Chance of rain 40 percent.

Tonight: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 64 to 71 in the valleys to around 60 above 4000 feet. Light winds. Chance of rain 40 percent.

Monday: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 77 to 85 in the valleys to around 67 above 4000 feet. Southeast winds up to 10 mph. Chance of rain 40 percent.

North Kaua’i

Rest Of Today: Mostly sunny with isolated showers. Highs 79 to 88. Northeast winds up to 10 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 66 to 74. Light winds. Chance of rain 20 percent.

Monday: Mostly sunny with isolated showers. Highs 79 to 88. East winds up to 15 mph. Chance of rain 20 percent.

East Kaua’i

Rest Of Today: Mostly sunny with isolated showers. Highs 78 to 89. East winds up to 10 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 65 to 78. Light winds. Chance of rain 40 percent.

Monday: Mostly sunny with isolated showers. Highs 76 to 88. South winds up to 10 mph shifting to the east around 10 mph in the afternoon. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A brief enhancement in shower activity through Monday morning in response to both vicinity troughing north of the state and higher moisture passing across the islands from the east. Overall, the region will remain relatively dry and stable the next couple of days. Cloudier, warm and muggy island weather is forecast Tuesday and Wednesday under weakened trade flow. Hurricane Kiko is approaching Hawaii from the southeast. Kiko's current forecast track remains north of the islands across the far northern offshore waters. While confidence is low concerning Kiko's early to mid week impacts, there is a possibly of higher statewide rainfall and elevated east-facing shore surf.

Discussion

This morning's synoptic pattern has a weak upper ridge axis just south of the islands that is being worked on by a southern- advancing 579 dam 500 mb dam low located approximately 400 miles north of Oahu. The associated trough draped across the far northwest offshore waters, along with Hurricane Kiko located about 700 miles east southeast of Hilo, Hawaii, have disrupted the downstream pressure gradient from a 1021 mb surface high centered 1,100 miles north-northeast of Big Island. The result will be lighter trade winds within an increasingly humid island environment. Light background trade flow will open the door for more wind-sheltered locales to experience local diurnal breezes. A surge of deeper, more moist-rich air embedded within light upstream trades as noted on this morning's shortwave infrared satellite imagery, in tandem with the weak instability of the trough in proximity of the northwest waters, is providing enough juice and lift, respectively, to generate more areawide shower activity through early Monday. Higher rain amounts will be confined to north and east-facing exposures and at higher elevation.
Category Three Hurricane Kiko (eye centered 17N144W at 3 AM HST) is moving west-northwest at around 15 mph. Kiko is forecast to continue to weaken as it approaches the Hawaiian Islands from the southeast. Kiko is currently forecast to be a hurricane when it reaches our far northeast offshore waters late Monday, weakening to a tropical storm as it travels over our northern offshore waters Tuesday night. A dry slot of air leading the cyclone will pass across the state Monday and briefly lower early day rain chances. Then rain chances will steadily increase from the east from late Monday through Wednesday or Thursday. Light trades will gradually back more northerly as Kiko passes off to the north through the middle of the week. Kiko is introducing a very high precipitable water air mass of around 2 inches to the area; near max values by early September standards. So, with a forecast north-northwest Kiko track, forecast confidence is the greatest that island weather during Kiko's passage will transition to cloudier and more humid under very benign winds and occasional showers. The greatest rainfall will likely fall along more eastern and northern upslope mauka or within higher terrain. This very moist air mass moving across the islands as Kiko passes to the north, combined with weaker steering flow over the island chain, may lead to periods of heavy rain along small scale breeze boundaries.
As of this morning, Kiko's main impacts still remain marine-based and focused on potentially high east-facing shore surf (please refer to the Marine section below for further details). While Kiko is anticipated to arrive in the far offshore waters Tuesday, there is enough inherent error in track and intensity to understand that tropical storm force conditions are possible (non-zero chances) across the far windward nearshore waters of Big Island and Maui County. Thus, interests in Hawaii and the surrounding waters should closely monitor Kiko's progression toward the state these next couple of days.

Aviation

Light and variable trades with land/sea breezes today. Low cigs and SHRA possible along windward and mauka areas. MVFR conds possible in SHRA, otherwise VFR should prevail. A slight increase in SHRA is anticipated tomorrow in relation to a trough west northwest of Hawaii.
Tropical Cyclone Kiko will approach the island chain from the southeast early this week. The National Hurricane Center is currently forecasting Kiko to pass north of the islands Tuesday. Any deviation south of this forecast track may result in wind and rain impacts to the state.
No AIRMETs are in effect.

Marine

No significant changes have been made to the forecast overnight. A weak trough will linger north of the state through today, resulting in gentle to moderate trade winds with localized land and sea breezes. As the trough drifts westward Monday, more moderate trade winds could make a brief return.
Attention then turns to Hurricane Kiko, which was located approximately 640 NM ESE of Hilo early this morning. Hurricane Kiko continues to track west northwest in the Central Pacific, and according to the latest forecast from the National Hurricane Center, is expected to enter our offshore waters Monday night as a hurricane. Kiko will then continue to move northwest through the offshore waters as it weakens to tropical storm status. The last few advisories from NHC have consistently kept Kiko just far enough away to keep the mention of possible tropical storm conditions out of the coastal waters forecast, but we will continue to monitor for future track updates as the system approaches. With that said, swell generated by Kiko will begin arriving today, peaking at or near High Surf Warning levels along east-facing shores Monday night and Tuesday.
Surf along east facing shores will steadily rise late today through the next couple of days as swell energy from Tropical Cyclone Kiko arrives. The surf may approach High Surf Advisory Criteria as early as Monday and possibly reach low end High Surf Warning levels Monday night into Tuesday during its peak. Surf heights will be highly dependent on the track and intensity of Kiko as it nears the state.
A moderate long period south-southwest swell will peak today helping to build surf above the summer average. As this swell declines on Monday, another reinforcing swell out of the south- southwest is expected on Tuesday. This should help maintain surf near or slightly above the summer average throughout the first half of the week. Additionally, multiple small pules of northwest swell energy will generate small surf along north facing beaches through next week.
Peak monthly high tides, combined with water levels running higher than predicted, may lead to minor flooding along the shoreline and in low lying coastal areas. A Coastal Flood Statement remains in effect through this afternoon.

Fire weather

Winds will remain well below critical fire weather thresholds the next few days. While humidity levels will steadily be on the rise, there will be brief periods of low early afternoon humidities within lower elevation, leeward interiors the next couple of days. Drier air will filter in across the state Monday and maintain low humidity, but winds will remain below critical fire weather thresholds. Showers may increase in coverage and intensity over many windward exposures beginning late Monday through the middle of the week as a result of the approach and passage of Tropical Cyclone Kiko well north of the state.

HFO Watches/Warnings/Advisories

None.

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