West Kaua’i

Rest Of Today: Mostly sunny with isolated showers. Highs 85 to 92 near the shore to around 77 above 3000 feet. South winds up to 10 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Isolated showers in the evening. Lows around 72 near the shore to around 61 above 3000 feet. Light winds. Chance of rain 20 percent.

Sunday: Mostly sunny with isolated showers. Highs 85 to 91 near the shore to around 77 above 3000 feet. Light winds. Chance of rain 20 percent.

South Kaua’i

Rest Of Today: Sunny. Isolated showers late in the morning. Highs 84 to 91. East winds around 10 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers after midnight. Lows 70 to 75. Northeast winds around 10 mph in the evening becoming light. Chance of rain 20 percent.

Sunday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 84 to 91. East winds up to 10 mph. Chance of rain 40 percent.

Kaua’i Mountains

Rest Of Today: Mostly sunny 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 40 percent.

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 63 to 70 in the valleys to around 58 above 4000 feet. Light winds. Chance of rain 50 percent.

Sunday: Partly sunny with scattered showers. Highs 77 to 85 in the valleys to around 68 above 4000 feet. Light winds. Chance of rain 50 percent.

North Kaua’i

Rest Of Today: Mostly sunny with isolated showers. Highs 79 to 87. East winds up to 10 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 65 to 73. East winds up to 10 mph in the evening becoming light. Chance of rain 30 percent.

Sunday: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 79 to 88. East winds up to 15 mph. Chance of rain 50 percent.

East Kaua’i

Rest Of Today: Mostly sunny with isolated showers. Highs 76 to 89. East winds up to 10 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 64 to 77. Light winds. Chance of rain 40 percent.

Sunday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 77 to 90. Light winds becoming east up to 10 mph in the afternoon. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Generally dry and stable conditions will prevail today. Cloudier, warm and muggy island weather is forecast early next week under weakened trades. There will be a slight increase in rain shower frequency and areal coverage Sunday into Monday in response to higher moisture and a vicinity upper low located north of the state. Tropical Cyclone Kiko will be approaching Hawaii from the southeast. Kiko's current forecast track is north of the islands across the far northern offshore waters. While confidence is low concerning Kiko's impacts to Hawaii early to mid next week, there is a possibly of higher statewide rainfall.

Discussion

Weak ridging currently resides over the region as an upper low approximately 700 miles north of Oahu slowly advances south and weakens the ridge. The associated trough north of the state has also disrupted the downstream pressure gradient from a 1022 mb surface high centered 1,700 miles north-northeast of Big Island. The result will be lighter overall trade winds that will allow more wind-sheltered local breezes to become more dominant. Sea breezes interacting with the background trade wind flow will produce thicker afternoon cloudiness and initiate light showers in such areas as Big Island's Kona and Ka'u regions and the leeward West Maui mountains. Subsidence from the mid-level ridging, along with a very dry and stable air mass above the 7k foot trade inversion, will be limiting factors for any measurable rain across the majority of the state through tonight. A ribbon of deeper, more moist-rich air embedded within light upstream trades, with the weak instability of the trough deepening and moving over the western half of the island chain, will provide enough umph to generate more statewide shower activity from Sunday into early Monday. Higher rain amounts will be confined to north and east- facing exposures and in higher elevation.
Category Four Hurricane Kiko has just passed into the Central Pacific basin at midnight and is moving west-northwest at 10 mph. Kiko is forecast to weaken as it approaches the Hawaiian Islands from the southeast and be a tropical storm as it passes in the vicinity of the far northern offshore waters of Hawaii Tuesday into Wednesday. 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 TC Kiko passes off to the north through the middle of next week. Kiko is also dragging in a very high precipitable water air mass of around 2 inches; near max values by early September standards. So, with a continued northerly track of Kiko, forecast confidence is highest that island weather during Kiko's passage will transition to cloudier and more humid under very weak winds and occasional showers. The greatest rainfall will likely occur along more eastern and northern upslope, higher terrain exposures. As of this morning, Kiko's main impacts will be marine-based (please refer to the marine section below). However, with Kiko's anticipated arrival in the local offshore waters still a good three to four days out, there will be inherent error in track and intensity. Thus, interests in Hawaii and the surrounding waters should monitor Kiko's progression toward the state through early next week.

Aviation

Light to moderate trade winds will prevail across many terminals. Trades will weaken this weekend as a trough north of the state advances south and moves closer to the island chain. Trades will be light enough to allow local breezes to dominant at such airfields as on Lanai (KHNY) and Big Island (HTO, HKO). Tropical Cyclone Kiko will approach the area from the southeast and is forecast to track well north of Hawaii next week. Brief periods of nocturnal low scattered to broken clouds and occasional showers will focus along windward exposures and or within higher terrain. MVFR ceilings and/or visibilities are possible within better organized, moderate-in-intensity showers.
There are currently no AIRMETs in effect and none are anticipated through the morning.

Marine

A weak trough will drop north of the state today into Sunday and cause trade winds to ease into the gentle to moderate range with localized sea breezes. As this feature slowly drifts westward on Monday, moderate trade winds will be allowed to briefly return.
Hurricane Kiko, approximately 900 NM ESE of Hilo, continues to track west northwest in the Eastern Pacific. The latest forecast from the National Hurricane Center has Kiko entering our offshore waters late Monday as a strong tropical storm or hurricane. The tropical cyclone may then skirt our coastal waters, north of the Big Island or Maui County on Tuesday. Please keep a close eye on the future National Hurricane Center forecast track updates as the system approaches.
Surf along east facing shores will steadily rise late Sunday through early next week as swell energy from Tropical Cyclone Kiko arrives. The surf may approach High Surf Advisory Criteria as early as Monday and possibly breach High Surf Warning levels Monday night into Tuesday during its peak. However, surf heights will be highly depended on the track and intensity of Kiko as it nears the state.
A moderate long period south-southwest swell will gradually fill in today and peak on Sunday 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 next week. 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 Sunday afternoon.

Fire weather

Humidities will briefly fall into the upper 30s to middle 40s once again this afternoon under dry and warm conditions. Winds will remain well below critical fire weather thresholds with light breezes forecast this weekend. Drier air will filter across the state Monday and briefly lower humidities, but weak winds will remain below critical fire weather thresholds. Showers may increase in coverage and intensity over many windward exposures early to mid next week as a result of the approach and passage of TC Kiko north of the state.

HFO Watches/Warnings/Advisories

None.

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