Photo Credit: Sebastien Gabriel

West Kaua’i

Today: Partly sunny with isolated showers. Highs around 84 near the shore to around 72 above 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows around 73 near the shore to around 67 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Friday: Mostly sunny early in the morning then becoming partly sunny. Scattered showers. Highs around 84 near the shore to around 72 above 3000 feet. Southeast winds up to 15 mph. Chance of rain 50 percent.

South Kaua’i

Today: Partly sunny. Numerous showers early in the morning, then scattered showers in the late morning and afternoon. Highs around 81. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 73. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Friday: Partly sunny with scattered showers. Highs around 81. East winds around 10 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Frequent showers early in the morning, then scattered showers in the late morning and afternoon. Highs 71 to 78 in the valleys to around 62 above 4000 feet. East winds up to 15 mph. Chance of rain near 100 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 66 to 71 in the valleys to around 62 above 4000 feet. East winds up to 10 mph. Chance of rain 60 percent.

Friday: Mostly cloudy. Numerous showers early in the morning, then scattered showers in the late morning and afternoon. Highs 71 to 78 in the valleys to around 62 above 4000 feet. Southeast winds up to 10 mph. Chance of rain 60 percent.

North Kaua’i

Today: Mostly cloudy. Frequent showers early in the morning, then scattered showers in the late morning and afternoon. Highs 74 to 83. East winds up to 15 mph. Chance of rain 90 percent.

Tonight: Mostly cloudy with scattered showers. Lows 68 to 74. Southeast winds up to 10 mph. Chance of rain 50 percent.

Friday: Partly sunny with scattered showers. Highs 74 to 83. Southeast winds up to 15 mph. Chance of rain 50 percent.

East Kaua’i

Today: Frequent showers early in the morning, then scattered showers in the late morning and afternoon. Highs 74 to 82. East winds 10 to 15 mph. Chance of rain near 100 percent.

Tonight: Mostly cloudy with scattered showers. Lows 64 to 75. Northeast winds up to 10 mph in the evening becoming light. Chance of rain 50 percent.

Friday: Partly sunny with scattered showers. Highs 74 to 82. Southeast winds up to 10 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Showery conditions will continue for windward and mauka areas of Oahu and Kauai this morning due to a lingering band of moisture. Although a drying trend is anticipated tonight through Saturday as the band of moisture moves out and our trades diminish, a few spotty interior and leeward afternoon showers associated with sea breezes are possible. A brief return of moderate to breezy trades is expected late Saturday through Monday as high pressure builds north of the area behind a passing front. Increasing moisture associated with low pressure forming west of the state could bring the rainfall chances and south-southeast winds back Tuesday through midweek.

Discussion

Early morning radar loop showed light to moderate showers continuing over windward Oahu and Kauai due to an area of moisture moving through and a band of low clouds associated with an old frontal boundary lingering in the area. The rainfall rates, however, have dropped quite a bit from what was observed earlier on Wednesday with peak overnight totals (through 2 AM HST) ranging from 0.5 to 2 inches. Streams on Oahu and Kauai have responded and steadily lowered through the night. Near-term guidance remains in decent agreement and shows a drying trend later today through Saturday as the moisture moves out and the upper ridge holds. Trades will persist today, then diminish and shift out of the southeast beginning tonight as the ridge shifts southward into the area. This light southeast background flow will allow land and sea breezes to form, which supports the best chance for spotty showers forming over our interior and leeward areas each afternoon.
Over the weekend, guidance reflects the progressive pattern continuing across the northern Pacific with another front passing to the north and an upper low closing off west of the state. While the moisture axis associated with the passing front is expected to remain north of the islands, a surface ridge quickly nosing eastward behind it will bring our moderate to breezy trades and windward showers back Saturday night through Monday.
Increasing moisture and instability associated with lowering upper heights as the previously mentioned upper low opens as it lifts northeast across the region will drive the the rain chances up for the state by Tuesday. Broad surface troughing near or west of the state could lead to the trades diminishing and shifting back out of the south to southeast by Tuesday. The probabilistic rainfall guidance supports this upward trend, especially over the western end of the state Tuesday through Wednesday.

Aviation

Light to moderate easterly flow, along with enhanced low level moisture, will allow for scattered showers to persist along windward locations through the day today. Periods of MVFR ceilings and visibility may accompany any of the more robust showers. Isolated showers may occasionally spill over the higher terrain and onto the leeward slopes.
AIRMET SIERRA remains in effect above 2000 feet for north through east sections of Kauai and Oahu due to tempo mountain obscuration from low clouds and showers.

Marine

Moderate to locally fresh east trade winds continue today and then veer to a more southeast direction as low pressure develops west of the Hawaiian Islands. Trades then quickly back to northeast as a cold front encroaches on the islands from the north late Saturday into Sunday. Locally strong winds can be expected behind the front, though its southward progress through the island chain remains uncertain. At this time, the strongest winds are most likely in the waters near and north of Kauai late Sunday night into Monday.
Long period energy associated from the northwest swell (320 degrees) has reached offshore buoys late last night as early forerunners are expected through the day. The initial surge of long period energy will fill in today before extra-large reinforcements will cause a sharp rise in the swell height tonight into early Friday morning. A High Surf Warning (HSW) is in effect from noon today through Friday for north and west facing shores most exposed to the swell. A High Surf Advisory (HSA) is possible for Big Island west facing shores as it builds down the island chain Friday. A Small Craft Advisory (SCA) has been issued for most waters for seas greater than 10 feet through Friday. Past events have suggested the potential for marginal to significant coastal impacts with periodic overtopping of the roadways late tonight into Friday morning due to the high tide and the peak of the swell.
Surf along east facing shores will remain rough and choppy for the next day or so, due to the combination of breezy trade winds and the decreasing north swell wrapping into exposed locations. Less choppy conditions are expected later in the week due to decreasing wind speeds, however locations exposed to northwest swell may still be impacted.
Surf along south facing shores will remain small through the rest of week. The next small, long-period south-southwest swell is expected to fill in over the weekend, keeping surf from going flat.

HFO Watches/Warnings/Advisories

High Surf Warning from noon today to 6 PM HST Friday for Niihau, Kauai Leeward, Waianae Coast, Oahu North Shore, Maui Windward West, Kauai North, Molokai Windward, Molokai North, Molokai West, Maui Central Valley North, Windward Haleakala.
Small Craft Advisory from noon today to 6 PM HST Friday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Alenuihaha Channel, Big Island Windward Waters.

Data Courtesy of NOAA.gov