West Kaua’i

Tonight: Partly cloudy with isolated showers. Lows 65 to 70 near the shore to around 58 above 3000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Wednesday: Sunny with isolated showers. Highs 79 to 86 near the shore to around 72 above 3000 feet. Southeast winds up to 10 mph. Chance of rain 20 percent.

Wednesday Night: Mostly clear. Lows 65 to 70 near the shore to around 58 above 3000 feet. Southeast winds up to 10 mph in the evening becoming light.

South Kaua’i

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows around 68. Light winds. Chance of rain 40 percent.

Wednesday: Partly sunny with scattered showers in the morning, then sunny in the afternoon. Highs 78 to 86. South winds up to 10 mph. Chance of rain 40 percent.

Wednesday Night: Mostly clear with isolated showers. Lows around 68. 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 59 to 67 in the valleys to around 56 above 4000 feet. Light winds. Chance of rain 40 percent.

Wednesday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 74 to 81 in the valleys to around 64 above 4000 feet. Light winds becoming south up to 10 mph in the afternoon. Chance of rain 40 percent.

Wednesday Night: Partly cloudy with isolated showers. Lows 58 to 67 in the valleys to around 56 above 4000 feet. Light winds. Chance of rain 20 percent.

North Kaua’i

Tonight: Partly cloudy with isolated showers. Lows 61 to 68. Southeast winds up to 10 mph. Chance of rain 20 percent.

Wednesday: Mostly sunny with isolated showers. Highs 75 to 83. South winds up to 10 mph in the morning becoming light. Chance of rain 20 percent.

Wednesday Night: Partly cloudy with isolated showers. Lows 61 to 69. Light winds. Chance of rain 20 percent.

East Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows 61 to 72. South winds up to 10 mph in the evening becoming light. Chance of rain 40 percent.

Wednesday: Partly sunny with scattered showers in the morning, then sunny in the afternoon. Highs 73 to 84. South winds up to 10 mph. Chance of rain 40 percent.

Wednesday Night: Partly cloudy with isolated showers. Lows 61 to 72. Light winds. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Light to occasionally moderate east to southeasterly winds are expected to persist through the remainder of the week and into the weekend. Light showers will focus across windward areas during the overnight hours and leeward and interior areas during the afternoon hours. A deep upper-level low will approach the islands early next week and bring southwesterly winds to the area, however confidence remains low with regards to the strength and positioning at this time.

Discussion

Latest observations show clouds and isolated showers easing across much of the state under predominately east to southeast flow as the pattern transitions back to land breezes. Rain gages across the state show 3 hour totals (as of 600 PM HST) in the 0.05″ to 0.10″ for a few leeward locations of Oahu and upwards of 0.05″ in most gage locations on the Big Island. Additionally, the stationary front is now roughly 100 nautical miles north of Kauai, as showcased on satellite imagery. This dissipating boundary is anticipated to continue retreating northward overnight as the associated low propagates northeastward toward the west coastline of CONUS. Meanwhile, model guidance hints at a new low moving eastward across the Pacific escorting in another front toward the islands before retrograding northwestward slowly.
Clouds and showers return to the leeward and interior sections of the islands tomorrow as seas breezes develop, and will continue to transition back and forth as such through the next few days. While generally moving into a more stability pattern, the wrench being thrown into the forecast is a perturbation across the primarily zonal flow through tomorrow, decreasing overall stability and resulting in periods of increased shower activity. Despite this, models are not doing a good job picking up on rainfall occurring over land, but instead retains it offshore, windward side of the islands.
As the next front moves toward the island chain, a hybrid of sorts between land-sea breezes and trade winds will occur, given the location of the broad upper- level ridge to the east of the islands, where winds will remain light to occasionally moderate from the southeast for the remainder of the week and into the transition of the weekend. During this time, islands within the immediate shadow of the Big Island will experience a rain shadow effect and will likely see little if any windward showers in light winds. While some showers will still be carried into windward areas on the east to southeast winds, the lighter flow will allow sea breezes to bring cloud buildups and a few light showers to leeward and interior areas each afternoon, and land breezes to help clear out leeward and interior areas overnight. However, shower activity will still remain limited overall as latest model guidance continues to show agreeance on upper-level ridging building in over the islands, increasing stability.
Thereafter, forecast confidence decreases quite a bit heading into next week as model guidance between the GFS and ECMWF, despite looking in far better agreement than this time yesterday. Latest model guidance currently suggests a deep, upper-level low developing northwest of the islands. While both models show this low, strength and positioning of the feature may play a factor in local wind speeds and direction, as well as create addition opportunities for moisture to move over the island chain from the southwest.

Aviation

Light to moderate large scale southeasterly winds will produce land and sea breezes over all islands northwest of the Big Island rain and wind shadow over the next 24 hours. Brief showers are possible, mostly VFR conditions will prevail.
No AIRMETs are currently in effect.

Marine

A stationary boundary over the north offshore waters, along with a weak ridge of high pressure settled over Hawaii, will result in gentle east to southeast winds over more west waters…moderate east to southeast winds over windward Maui County and around Big Island through Wednesday. As the stationary front begins to gradually shift north and dissipate, high pressure will become better established across the region. This will result in generally light to gentle easterlies, more moderate in magnitude over windward Maui and around Big Island, from Thursday through the weekend. Large scale east or southeast winds may become light enough to initiate localized daytime coastal onshore sea breezes and overnight offshore land breeze behavior. Winds are forecast to veer to the south early next week in response to a developing low far northwest of the offshore waters.
The current small to moderate size, short to medium period northwest (330 degree) swell is steadily declining and will continue to fall through Wednesday. The High Surf Advisory along many north and west-facing shores today has been cancelled as surf will quickly drop off through tomorrow. A series of small north (350-010 degree) swells will begin arriving from Thursday and persist through the weekend. This will produce a boost in north-facing surf and heights will remain well below advisory thresholds.
South-facing shores should remain small with some background long period south southwest swell expected to arrive Thursday or Friday. East-facing shore chop will remain small due to the absence of strong trades. As the series of small north swells fill in beginning Thursday, select east-facing exposures should experience a small bump in surf from north wrap.

HFO Watches/Warnings/Advisories

None.