West Kaua’i

Tonight: Mostly clear. Isolated showers in the evening. Lows 70 to 75 near the shore to around 61 above 3000 feet. Light winds. Chance of rain 20 percent.

Sunday: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs 85 to 91 near the shore to around 77 above 3000 feet. Light winds. Chance of rain 20 percent.

Sunday Night: Mostly clear. Isolated showers in the evening. Lows 71 to 76 near the shore to around 62 above 3000 feet. Light winds. Chance of rain 20 percent.

South Kaua’i

Tonight: Partly cloudy. Isolated showers after midnight. Lows around 73. Northeast winds around 10 mph. Chance of rain 20 percent.

Sunday: Mostly sunny with isolated showers. Highs 84 to 91. Light winds. Chance of rain 20 percent.

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

Kaua’i Mountains

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 40 percent.

Sunday Night: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 64 to 71 in the valleys to around 59 above 4000 feet. Light winds. Chance of rain 40 percent.

North Kaua’i

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

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

East Kaua’i

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 64 to 78. Northeast winds up to 10 mph in the evening becoming light. Chance of rain 40 percent.

Sunday: Mostly sunny with isolated showers. Highs 77 to 89. Light winds becoming southeast up to 10 mph in the afternoon. Chance of rain 20 percent.

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

Detailed Forecast

Synopsis

Generally dry and stable conditions will prevail through tonight. An uptick in shower activity is expected Sunday into Monday morning in response to a passing band of moisture and an upper low approaching from the north. Confidence is increasing that Tropical Cyclone Kiko will pass far enough north of the state next week to decreases the likelihood of any direct impacts to Hawaii. However, life-threatening surf along east-facing shores will be possible along with an increased potential for statewide rainfall.

Discussion

Weak high pressure north of the islands remains disrupted by a surface low/trough, maintaining light to moderate trades this afternoon. The weaker gradient has allowed localized sea breezes to develop, producing clouds and isolated light showers over leeward and interior areas. Rainfall has been limited by subsidence from mid-level ridging and a dry airmass filtering in above the trade wind inversion.
From Sunday into early Monday morning, a band of deeper moisture embedded within the lighter trades, together with increasing instability from an approaching upper low, will bring a modest increase in showers. Most activity will focus over windward and mauka areas overnight, while sea breeze convergence may trigger brief heavy showers over leeward and interior areas Sunday afternoon.
A narrow dry slot will move across the islands on Monday, briefly lowering relative humidities and providing a drier feel with moderate trades. These conditions will be short-lived, as the leading edge of tropical moisture associated with Hurricane Kiko (extending far from its center) will reach the eastern end of the state Monday afternoon, then spread westward across the island chain by Tuesday morning as Kiko begins to pass north of the state.
As of 330 PM HST this afternoon, Hurricane Kiko was a Category 4 system located a little less than 900 miles east-southeast of Hilo, moving west-northwest at 12 mph. Kiko is forecast to weaken as it moves across the Central Pacific and passes north of the main Hawaiian Islands. While forecast uncertainty remains in regards to track and intensity, confidence is increasing in that the tropical storm-force winds will remain confined north of the island chain. The primary impacts for Hawaii are expected to be marine-related, with large and potentially life-threatening surf along east-facing shores. Please see the marine section below for more details. In addition, the moist airmass moving across the islands as Kiko passes to the north, combined with weaker winds over the area as the trades are blocked may lead to periods of heavy showers over island interiors each afternoon through midweek with sea breeze convergence along with a windward focus during the overnight periods.

Aviation

Winds will remain light and variable with land and sea breezes through the weekend as an upper level low to the north moves south towards the islands and weakens the ridge. A weak mid level trough with increased moisture could move through the islands tomorrow and modestly increase clouds and showers. Brief periods of MVFR will be possible in any showers and could be a little more widespread as the trough moves through tomorrow afternoon.
Tropical Cyclone Kiko will then approach the island chain next week and the National Hurricane Center (NHC) is currently forecasting a passage to the north of the islands. Any deviation south of the track could result in impacts to the State. Stay tuned for further updates and details.
There are currently no AIRMETs in effect and none are anticipated through tonight.

Marine

No significant changes to the forecast with the afternoon package. The forecast track for Hurricane Kiko has trended north away from the islands, decreasing the chances for direct impacts. Swell generated by Kiko will arrive in the islands on Sunday, peaking at or near High Surf Warning levels Monday night and Tuesday.
A weak trough north of the state through Sunday is causing the trade winds to ease to the gentle to moderate range with localized land and sea breezes. As the trough drifts to the west Monday, moderate trade winds may make a brief return.
Hurricane Kiko, approximately 775 NM ESE of Hilo, continues to track west northwest in the Central Pacific. The latest forecast from the National Hurricane Center has Kiko entering our offshore waters late Monday night as a strong tropical storm or hurricane. The last few forecast tracks for Kiko have trended north, taking the track further from the coastal waters, and lowering the probability for tropical storm conditions in the coastal waters. We will continue to monitor 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 reach low end High Surf Warning levels Monday night into Tuesday during its peak. 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 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

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 winds will remain below critical fire weather thresholds. Showers may increase in coverage and intensity over many windward exposures beginning late Monday through 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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