Photo Credit: Sebastien Gabriel

West Kaua’i

Today: Mostly sunny with isolated showers. Highs around 84 near the shore to around 72 above 3000 feet. Southeast winds around 10 mph shifting to the southwest in the afternoon. Chance of rain 20 percent.

Tonight: Mostly clear with isolated showers. Lows around 66 near the shore to around 55 above 3000 feet. Light winds becoming northeast around 10 mph after midnight. Chance of rain 20 percent.

Tuesday: Mostly sunny with isolated showers. Highs around 83 near the shore to around 71 above 3000 feet. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 20 percent.

South Kaua’i

Today: Mostly sunny. Highs around 83. Light winds becoming southeast around 10 mph in the afternoon.

Tonight: Partly cloudy with isolated showers. Lows 62 to 67. Northeast winds around 10 mph. Chance of rain 20 percent.

Tuesday: Mostly sunny with isolated showers. Highs around 82. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Kaua’i Mountains

Today: Mostly sunny with isolated showers. Highs 71 to 79 in the valleys to around 66 above 4000 feet. South winds around 10 mph shifting to the east in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 55 to 60 in the valleys to around 49 above 4000 feet. Northeast winds up to 10 mph shifting to the east after midnight. Chance of rain 20 percent.

Tuesday: Mostly sunny in the morning then becoming partly sunny. Breezy. Scattered showers. Highs 70 to 78 in the valleys to around 65 above 4000 feet. East winds 10 to 20 mph. Chance of rain 40 percent.

North Kaua’i

Today: Mostly sunny. Isolated showers in the afternoon. Highs 76 to 83. North winds up to 10 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 58 to 67. Southeast winds around 10 mph. Chance of rain 20 percent.

Tuesday: Mostly sunny with isolated showers. Highs 75 to 82. East winds 10 to 15 mph. Chance of rain 20 percent.

East Kaua’i

Today: Sunny. Isolated showers in the afternoon. Highs 76 to 83. Southwest winds around 10 mph shifting to the northeast in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 56 to 70. Northeast winds around 10 mph. Chance of rain 20 percent.

Tuesday: Mostly sunny with isolated showers. Highs 75 to 82. East winds 10 to 15 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A weak surface ridge in the vicinity of Hawaii will maintain light and variable winds, and keep showers limited across the islands today. This ridge is expected to build as it lifts slowly north, which will allow locally breezy trade winds to gradually return from late tonight through Tuesday. The trade winds will transport some low clouds and brief showers mainly along windward facing slopes from tonight into mid-week. The winds will likely trend weaker starting Wednesday night as a front approaches Kauai from the northwest. In addition, expect a significantly drier weather pattern over most of the state from Thursday into the New Year's Holiday Weekend.

Discussion

A nearly east to west oriented surface ridge, which remains in the vicinity of the northern islands early this morning, appears to be lifting slowly northward. The close proximity of this feature to the state is maintaining light and variable background winds across Hawaii. As a result, local land breezes are dominating the winds over each of the individual islands. The latest loops of satellite imagery and radar reflectivity data show minimal cloud cover over the islands due to these drainage winds. There are a few small patches of low clouds with embedded light showers detected over the ocean west of the leeward Big Island and northwest of Oahu. Otherwise, low clouds and showers are nearly non-existent over the ocean surrounding the islands.
A nearly east to west oriented mid-tropospheric ridge continues to propagate over the region from the west early this morning. The forecast trends indicate the light wind regime will likely persist into this afternoon. We will also continue to experience stable atmospheric conditions due to the ridging aloft. Local sea breezes are expected to become established over most of the islands this afternoon. This may allow some low clouds and a few spotty showers to form over leeward and interior sections. The latest model guidance indicates the surface ridge will continue to gradually lift north, and build from later today and tonight through Tuesday. This will likely tighten the pressure gradient initially over the eastern islands tonight, with locally breezy trade winds returning across the most of the state Tuesday. The trade wind weather pattern will focus some low clouds and brief trade showers mainly along windward sections from late tonight into Wednesday. The greatest coverage of low clouds and trade showers will tend to be during the late night through the early morning hours.
A new front is expected to push down toward Kauai from the northwest by Wednesday night. This will once again weaken the surface ridge north of the islands, which will disrupt the trade wind flow. As result, expect light and variable background winds, which will allow a pattern of alternating afternoon sea breeze and nighttime land breeze circulations to become established over each of the individual islands from Thursday into the New Year's Holiday Weekend. In addition, the forecast guidance shows low- level moisture values will decrease later this week. These drier conditions combined with the stable atmosphere due to the mid- level ridge will likely limit low clouds and showers during the end of the work week, and most likely continuing into next weekend.

Aviation

The ridge over the islands will slowly lift northward, and stall north of Kauai later night. This will maintain light winds and a stable airmass over the region today. Expect the light winds to give way to afternoon sea breezes that could produce isolated areas of MVFR in showers. As the ridge lifts north, gentle easterly trade winds will develop from east to west today and tonight. No AIRMETs are in effect, and none are expected today.

Marine

High pressure ridging at all levels is currently anchored across the region. A weak surface pressure gradient will result in light winds across most nearshore waters this morning. Surface high pressure will subtly center itself just northeast of the state the next couple of days. This will slightly tighten the gradient up across the island chain and produce moderate to fresh trade winds. Stronger trades will likely channel through the notoriously windier areas around Maui County and Big Island tonight through early Wednesday. A series of approaching fronts from the northwest will weaken the ridge from late Wednesday through New Year's Day on Sunday. These nearing fronts will veer light winds more east to southeast late this week. After a day of generally moderate east to southeast winds Wednesday, light southeast to (more western island) variable breezes will occur across many coastal zones Thursday and Friday. The year will end with gentle to moderate east trades.
The ongoing moderate size, medium period northwest (310-320 degree) swell is slowly declining through Tuesday. To account for this slow fall, the High Surf Advisory (HSA) will remain in effect for north and west-facing shores (except Big Island) until mid to late morning. The next moderate size, medium period northwest (310 degree) swell will build in Wednesday and potentially lift north and west-facing shore surf back up to HSA levels Thursday and Friday. A slightly larger northwest swell arriving around New Year's Day may also generate a HSA event next Monday. East-facing shore wind wave chop will remain small but a short term increase in easterly winds Tuesday will likely add another foot or two onto east faces.

HFO Watches/Warnings/Advisories

High Surf Advisory until noon HST today for north and west facing shores of Kauai, Niihau, Oahu, and Molokai, and for north facing shores of Maui.
Small Craft Advisory until noon HST today for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters.

Data Courtesy of NOAA.gov