West Kaua’i

Today: Partly sunny with scattered showers. Highs 86 to 93 near the shore to around 78 above 3000 feet. Light winds. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 72 to 77 near the shore to around 63 above 3000 feet. Light winds. Chance of rain 40 percent.

Wednesday: Partly sunny with scattered showers. Highs 86 to 91 near the shore to around 77 above 3000 feet. South winds up to 10 mph. Chance of rain 50 percent.

South Kaua’i

Today: Partly sunny with scattered showers. Highs 84 to 92. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows around 75. Northeast winds up to 10 mph. Chance of rain 30 percent.

Wednesday: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs 82 to 91. Light winds becoming south around 10 mph in the afternoon. Chance of rain 40 percent.

Kaua’i Mountains

Today: Mostly cloudy. Scattered showers in the morning, then numerous showers in the afternoon. Highs 77 to 86 in the valleys to around 68 above 4000 feet. East winds up to 10 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with scattered showers. Lows 65 to 72 in the valleys to around 60 above 4000 feet. Northeast winds up to 10 mph. Chance of rain 50 percent.

Wednesday: Partly sunny with scattered showers. Locally heavy rainfall possible in the afternoon. Highs 77 to 85 in the valleys to around 67 above 4000 feet. Light winds. Chance of rain 50 percent.

North Kaua’i

Today: Partly sunny with scattered showers. Highs 79 to 89. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows 67 to 74. East winds up to 10 mph shifting to the southeast after midnight. Chance of rain 50 percent.

Wednesday: Partly sunny with scattered showers. Highs 79 to 88. South winds up to 10 mph. Chance of rain 50 percent.

East Kaua’i

Today: Partly sunny with scattered showers. Highs 77 to 89. Northeast winds up to 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows 66 to 78. Northeast winds around 10 mph in the evening becoming light. Chance of rain 50 percent.

Wednesday: Partly sunny with scattered showers. Locally heavy rainfall possible in the afternoon. Highs 76 to 89. South winds up to 10 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Tropical Storm Kiko will continue to pass north of the islands today and Wednesday, disrupting the trade winds, producing areas of heavy rainfall, and generating large surf along east facing shores. Moderate trade winds and a typical pattern of windward rainfall will return on Thursday through early next week.

Discussion

This morning's radar and satellite imagery show a band of deep tropical moisture working its way across Oahu and Kauai. This feature brought a round of showers from east to west across the island chain overnight, some of which produced brief heavy downpours with several locations receiving about a quarter of an inch of rain.
As of 3:00 AM HST this morning, Tropical Storm Kiko was located a little over 200 miles NE of Hilo, moving west-northwest and continuing to weaken. While no direct impacts to Hawaii are expected from this tropical cyclone, its accompanying tropical airmass will continue to provide deep moisture to the state through Wednesday. As Kiko passes to the north, it will shut down the trades across the eastern half of the state today and the western half by this evening. This lighter wind pattern will allow for sea breezes to develop, which will kick off midday leeward and interior showers. Given the abundant available moisture and instability provided by a broad upper level low northwest of Kauai, some of these showers could produce brief heavy downpours, with an isolated thunderstorm or two possible over interior portions of the Big Island.
Moderate east-southeasterly trades will gradually rebuild from east to west across the island chain late tonight into Wednesday as Kiko further clears the area and the surface high to the northeast regains control. However, lingering tropical moisture and instability from the upper level low will keep the atmosphere primed for additional shower activity on Wednesday. Sea breeze activity over the western end of the state may bring another round of brief heavy afternoon showers to interior and leeward portions of Kauai and Oahu before the trades build back in.
A more typical trade wind pattern is expected Thursday through early next week as mid level ridging returns and drier air filters in. In this regime, moderate trades will focus light showers over windward and mauka areas, during the overnight and early morning hours, with leeward areas remaining mostly dry.

Aviation

Tropical Storm Kiko will pass north of the island chain today and act to disrupt typical trade wind flow. Light winds, especially along the leeward coasts, will allow for the development of a nocturnally driven sea breeze/land breeze pattern. Out ahead of the tropical system, increasing moisture and instability will aid in the development of mainly interior afternoon and evening showers. Some of the showers could be heavy with associated MVFR and isolated IFR ceilings and visibility. In addition, enough instability may exist for some pop up thunderstorms over interior portions of the Big Island. VFR conditions expected elsewhere.
AIRMET Sierra for mtn obsc is in effect for north through east sections of Kauai, Oahu, Molokai, and Maui above 2000 ft. Some improvement is expected later this morning, though AIRMET Sierra may be needed for interior sections of the islands this afternoon.

Marine

No significant changes to the forecast this morning. Tropical Cyclone Kiko remains the focus weather in the short term with regards to the swell generated by the system. The Hilo buoy saw an increase in swell shortly after sunset, and additional increases are expected through tonight.
Tropical Storm Kiko is about 180 NM NE of Hilo during the pre-dawn hours, and is expected to continue to track to the NW today. As it does so, it is disrupting the trade wind flow, causing winds over the coastal waters to weaken to gentle to moderate background northeast flow.
Kiko is moving through the offshore waters to the northeast of the islands. A Tropical Storm Warning is in effect for the offshore waters with Tropical Storm conditions expected over the E and NE offshore waters through Wednesday. Although no wind impacts are expected over the coastal waters, a quick rise of wave heights are expected tonight into Tuesday as Kiko passes.
The latest buoy observations from Hilo showed a rise in energy across the 12-14 second spectral bands during the evening, and throughout the night. With Kiko expected to make its closest approach to the Hawaiian Islands during the next 12-24 hours, we expect another quick rise in wave heights over the western half of the state today. Although peak surf heights are expected to be short-lived, a rapid rise of east swell should produce dangerous conditions along east facing shores. A High Surf Warning remains in effect for the Big Island, Maui, and Molokai, and starts for Oahu and Kauai this morning. Surf heights are expected to have peaked for the Big Island over the next couple of hours, for Maui County in the next few hours, and mid day into the afternoon for Oahu and Kauai.
A reinforcing swell out of the south-southwest is expected today. 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 throughout the week. A short- lived northeast swell is possible for select exposures as Kiko passes to our north.

Fire weather

Decreased winds and increased humidity with higher chances for rainfall are expected through Wednesday as Tropical Storm Kiko passes northeast and north of the state. A return to moderate and stable trade winds will occur on Thursday, though conditions are expected to remain below critical fire weather thresholds.

HFO Watches/Warnings/Advisories

High Surf Warning until 6 PM HST this evening for Olomana, Kauai East, Kauai South, East Honolulu, Koolau Windward.
High Surf Warning until 6 PM HST this evening for Maui Windward West, Molokai Windward, Molokai Southeast, Windward Haleakala, Kipahulu, Big Island Southeast, Big Island East, Big Island North.

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