Photo Credit: Brendan Stephen

West Kaua’i

Rest Of Today: Sunny. Isolated showers in the afternoon. Highs around 84 near the shore to around 72 above 3000 feet. Light winds. Chance of rain 20 percent.

Tonight: Partly cloudy. Lows 64 to 70 near the shore to around 57 above 3000 feet. Light winds becoming northeast up to 10 mph after midnight.

New Years Day: Mostly sunny. Highs 81 to 86 near the shore to around 72 above 3000 feet. Light winds.

South Kaua’i

Rest Of Today: Sunny. Highs 81 to 87. East winds around 10 mph shifting to the southeast in the afternoon.

Tonight: Mostly clear. Lows 63 to 68. North winds up to 10 mph.

New Years Day: Sunny. Isolated showers in the afternoon. Highs 80 to 86. Northeast winds around 10 mph. Chance of rain 20 percent.

Kaua’i Mountains

Rest Of Today: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs 73 to 79 in the valleys to around 64 above 4000 feet. Southeast winds up to 15 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 58 to 63 in the valleys to around 54 above 4000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

New Years Day: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs 73 to 79 in the valleys to around 64 above 4000 feet. East winds up to 10 mph. Chance of rain 20 percent.

North Kaua’i

Rest Of Today: Mostly sunny with isolated showers. Highs 74 to 83. East winds up to 10 mph in the morning becoming light. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 60 to 68. Light winds becoming east up to 10 mph after midnight. Chance of rain 20 percent.

New Years Day: Mostly sunny with isolated showers. Highs 74 to 83. Light winds becoming northeast around 10 mph in the afternoon. Chance of rain 20 percent.

East Kaua’i

Rest Of Today: Mostly sunny with isolated showers. Highs 73 to 84. Light winds becoming southeast around 10 mph in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 59 to 70. Light winds. Chance of rain 20 percent.

New Years Day: Mostly sunny with isolated showers. Highs 73 to 83. Light winds becoming east around 10 mph in the afternoon. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Moderate trade winds will will hold around the Big Island, while a nearby surface ridge produces lighter east to southeast winds across the rest of the state for the next few days. Very stable and somewhat dry conditions will continue. Stronger trade winds are due during the middle of next week, possibly pushing a a dissipating front over the islands.

Discussion

Trade winds are backing off over all islands and shifting southeasterly near Kauai, as a surface ridge has been pushed to within a couple hundred miles northwest of the state. Meanwhile, a strong ridge aloft is maintaining very stable conditions with an inversion based just over 5,000 ft, and since low level moisture is somewhat limited, modest showers have been confined to windward slopes from the Big Island to Oahu overnight.
Through the holiday weekend, moderate trades will hold near the Big Island, but as a surface ridge meanders just north of Kauai, the rest of the state will experience alternating light to gentle easterly to southeasterly winds. An impressive zone, or west to east flowing, jet stream will remain locked between 30N and 40N, keeping a strong mid to upper level ridge over the islands. The resulting stability and a lack of significant low level moisture will keep showers relatively limited and light, with highest chances of light rainfall persisting over windward slopes. Daytime sea breezes will produce clouds and perhaps a light shower over some leeward terrain each afternoon.
Taking a closer look at New Year's Eve forecast, chances for rainfall look to be relatively low overall, with the highest odds for light showers over windward areas from the Big Island to Oahu. The weaker trade winds will allow land breezes to set up in most areas, pointing toward rather stagnant conditions and poor smoke dispersion as we enter the new year.
An increase in trade winds is possible during the middle of next week. Subtle troughs within a strong zonal jet stream are notoriously fickle when trying to time this far out, but both the GFS and ECMWF are showing a weak front pushing toward the islands with a following surface high driving an increase in northeasterly trade winds mid week. However, the GFS is running about 18 hours slower than the ECMWF with the shallow front reaching the state sometime Tuesday or Wednesday. Both models show the front to be very shallow and likely to only provide a boost in windward rainfall. Late next week, expect somewhat dry conditions and moderate trade winds.

Aviation

A weak surface ridge just north of the state will keep light to moderate winds in the forecast with land and sea breezes over each island. Stable conditions aloft will limit cloud development and shower activity.
No AIRMETs in effect.

Marine

A weakening front north of the state has pushed the ridge axis across the north offshore waters closer to the islands. This will result in lighter weekend east to southeast winds with more variable breezes occurring over far western waters. While a New Year's Day front approaching from the northwest will ride overtop this regional ridging, the next in the series of fronts will pass across the island chain during the middle of next week. Surface high pressure behind this boundary will back moderate to fresh winds northeast Tuesday through Thursday.
The current moderate size, medium period west northwest swell that peaked Friday is holding steady. The very slow decline of this ongoing swell through Sunday afternoon will keep Niihau, Kauai and Oahu's north and west-facing shore surf heights at High Surf Advisory levels through the afternoon. A storm complex near the date line will generate a larger, longer period west northwest (310-320 degree) swell that will arrive on this swell's heels late tomorrow into Monday. This swell will likely produce warning level surf along many north and west-facing shores Monday.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 PM HST this evening for north and west facing shores of Niihau, Kauai, and Oahu.

Data Courtesy of NOAA.gov