Photo Credit: Brendan Stephen

West Kaua’i

Today: Mostly sunny. Breezy. Scattered showers early in the morning, then isolated showers in the late morning and afternoon. Highs around 80 near the shore to around 69 above 3000 feet. East winds up to 25 mph. Chance of rain 50 percent.

Tonight: Partly cloudy. Breezy. Isolated showers in the evening, then scattered showers after midnight. Lows 63 to 70 near the shore to around 53 above 3000 feet. East winds up to 25 mph. Chance of rain 50 percent.

Thursday: Breezy. Mostly sunny with isolated showers. Highs around 81 near the shore to around 70 above 3000 feet. East winds up to 25 mph increasing to 10 to 25 mph in the afternoon. Chance of rain 20 percent.

South Kaua’i

Today: Partly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 77. Northeast winds 15 to 25 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 60 to 69. Northeast winds 15 to 20 mph. Chance of rain 50 percent.

Thursday: Partly sunny. Windy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 78. Northeast winds 15 to 30 mph. Chance of rain 70 percent.

Kaua’i Mountains

Today: Mostly cloudy. Breezy. Numerous showers early in the morning, then scattered showers in the late morning and afternoon. Highs 68 to 74 in the valleys to around 60 above 4000 feet. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 70 percent.

Tonight: Mostly cloudy. Breezy. Numerous showers in the evening, then frequent showers after midnight. Lows 52 to 60 in the valleys to around 48 above 4000 feet. East winds 10 to 25 mph. Chance of rain 90 percent.

Thursday: Mostly cloudy. Breezy. Frequent showers in the morning, then scattered showers in the afternoon. Highs 69 to 75 in the valleys to around 61 above 4000 feet. East winds 10 to 25 mph. Chance of rain 80 percent.

North Kaua’i

Today: Partly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 70 to 80. East winds up to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 57 to 68. East winds up to 15 mph. Chance of rain 50 percent.

Thursday: Breezy. Partly sunny with scattered showers. Highs 71 to 81. East winds up to 25 mph increasing to 10 to 25 mph in the afternoon. Chance of rain 50 percent.

East Kaua’i

Today: Breezy. Mostly cloudy with scattered showers. Highs 69 to 79. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 53 to 71. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Thursday: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 70 to 80. Northeast winds 10 to 25 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

Breezy easterly trade winds will become strong and gusty later today through the second half of the week as high pressure strengthens north of the state. Windward shower coverage may increase through this period, with some showers occasionally making it to leeward areas of the smaller islands. Drier and more stable conditions will return over the weekend, with the easterly trades easing into the moderate to breezy range. Rainfall chances could trend up again early next week as an upper disturbance moves through.

Discussion

Guidance remains in good agreement through the second half of the week and shows high pressure building north of the state. The easterly trades will respond and become strong beginning later today, then likely strong enough for localized wind advisories through the day Thursday over the typically windier locations of Maui County and the Big Island. In addition to the strengthening winds, windward shower coverage could trend up due to a combination of a weak mid- to upper-level trough and a sufficient amount low-level moisture in the area. Some of these showers will manage to make it over to leeward areas of the smaller islands, especially overnight through the mornings. Rainfall accumulations should remain light.
Drier and more stable conditions will briefly return over the weekend as upper heights rise and PWs dip to around an inch. Trade winds are expected to ease into the moderate range due to a weakness forming in the ridge as a front passes to the north.
The forecast confidence lowers early next week due to significant differences shown between the various model solutions. While the GFS solutions are more aggressive and depict the tail-end of the aforementioned front moving through the area with strong northerly winds trailing it, the ECMWF shows it hanging up to the north with easterly trades holding (agrees with the blended guidance). Regardless of these differences, the attendant upper trough digging southward over the region drawing moisture into the area should be enough to support a transition to a wetter pattern Monday through midweek.

Aviation

Moderate to breezy easterly trades will continue through the remainder of this morning as surface high pressure remains anchored to the north of the state. Scattered showers will mainly be confined to windward locations with the occasional spill over to leeward sides. Brief periods of MVFR ceilings and visibility may occur with any of the more robust showers. By this afternoon, trades will strengthen further and become windy at times. This stronger flow will persist this evening into tonight and bring scattered to numerous showers to windward locations.
AIRMET Sierra has been issued above 2000 feet for north through east sections of Oahu due to tempo mountain obscuration from low clouds and showers.

Marine

High pressure north of the main Hawaiian Islands will move eastward and strengthen over the next few days, resulting in increased trade wind speeds across local waters through the rest of the work week. The Small Craft Advisory (SCA) remains in effect for the typical windy zones around Maui County and the Big Island but has been expanded to include windward and leeward waters around Maui County and Oahu.
Strong trades will create rough and choppy surf along east facing shores which will continue into next week. Moderate west- northwest (310 degree) swell will gradually decrease today. Expect additional small northwest (310-320 degree) swells from Thursday into early next week. Mainly background surf will continue for south facing shores through the weekend with some long period energy arriving early next week.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Thursday for Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Maui County Leeward Waters, Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov