Photo Credit: Sebastien Gabriel

West Kaua’i

Today: Breezy. Mostly sunny with isolated showers. Highs around 83 near the shore to around 70 above 3000 feet. Northeast winds up to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers after midnight. Lows around 68 near the shore to around 58 above 3000 feet. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Wednesday: Mostly sunny with isolated showers. Highs around 84 near the shore to around 70 above 3000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

South Kaua’i

Today: Partly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 78 to 83. Northeast winds 10 to 20 mph. Chance of rain 40 percent.

Tonight: Breezy. Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows around 67. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Wednesday: Partly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 77 to 83. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Breezy. Partly sunny with scattered showers. Highs 70 to 77 in the valleys to around 61 above 4000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows 61 to 66 in the valleys to around 56 above 4000 feet. East winds 10 to 25 mph. Chance of rain 70 percent.

Wednesday: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 69 to 77 in the valleys to around 61 above 4000 feet. East winds 10 to 25 mph. Chance of rain 70 percent.

North Kaua’i

Today: Partly sunny with scattered showers. Highs 72 to 83. East winds up to 15 mph. Chance of rain 40 percent.

Tonight: Mostly cloudy with scattered showers. Lows 61 to 70. East winds 10 to 15 mph. Chance of rain 50 percent.

Wednesday: Partly sunny with scattered showers. Highs 72 to 84. East winds 10 to 15 mph. Chance of rain 50 percent.

East Kaua’i

Today: Partly sunny with scattered showers. Highs 70 to 81. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 61 to 69. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Wednesday: Partly sunny with scattered showers. Highs 69 to 80. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Trade winds will gradually ease today as weak troughing passes by to our north. Modest rainfall brought in by the trades will favor windward slopes. Stronger trades and wetter conditions will return Wednesday and last into the weekend before trades decrease again early next week.

Discussion

Middle and high clouds, marking the western flank of an upper trough just east of the islands, have moved away to the northeast, revealing a timely view of low clouds. Meanwhile, high pressure far northeast of the islands continues to drive moderate trade winds across local waters this morning. Weak surface troughing passing to the north of the islands will put a dent in the subtropical ridge associated with the high, resulting in decreased trades through today. Surface winds are out of the east, but may be weak enough to allow development of local sea breezes across sheltered leeward areas this afternoon. Overnight soundings show we have a rather moist but stable airmass, with about 1.6 inches of PW and positive lifted index values. Total rainfall remains light given airmass stability. The current pattern will continue through the day today, with spotty light showers possible across leeward areas this afternoon and continued light showers across windward areas within trade flow. Leeward clouds and showers will decrease after nightfall.
Expect a return to breezy and gusty trade winds Wednesday, lasting into Friday, as a strong high moves north of the state from the west and weak troughing lifts out to the northeast. Models show a shortwave upper trough passing by Wednesday through Friday, possibly increasing instability. This may trigger a wetter tradewind pattern through Friday. Models also depict a band of moisture from a remnant front embedded in the tradewinds which may boost windward rainfall Friday or Saturday. Trades may decrease again heading into early next week as the high to the north weakens and moves off to the east.

Aviation

Light to moderate trade winds will gradually ease as high pressure to the northeast of the state shifts eastward over the next day or two. Clouds and showers carried in by the trade wind flow will continue to favor Windward slopes and coasts and be most active in the late night and morning hours.
AIRMET Sierra is currently in effect for occasional mountain obscuration along windward coasts of Oahu, Molokai, and Maui. Conditions are expected to improve by mid morning.
Meanwhile, the bands of high clouds that covered Hawaii yesterday have begun to move off to the east northeast in response to the shifting upper level jet.

Marine

A large area of high pressure centered approximately 900 nautical miles northeast of Oahu is continuing its east drift. This positioning has relaxed the pressure gradient back toward the state and weakened resultant trade winds to moderate magnitudes. The next surface high centered far northwest of the state will build in north of the islands through mid week and again re- tighten the gradient across the region. This will be re- strengthen winds back to fresh to locally strong speeds by Tuesday evening. Trades may reach gale force within the Alenuihaha Channel and south of Big Island by Wednesday night or early Thursday morning. A Wednesday Small Craft Advisory (SCA) for the windier eastern island channels and bays will likely need to be expanded to cover more western waters by Thursday. Trade winds will experience an overall minor decline this weekend but SCA conditions will likely still be in place over the typically windy waters surrounding Maui County and Big Island through early next week.
The moderate size west-northwest (300-330 degree) swell that peaked earlier Monday will gradually fall the next couple of days. Combined seas remain rather high but a reflection of both this declining swell and a mix of east southeast wind waves that have been generated from recently fresh winds over and upstream of the islands. Additonal pulses of small size, medium period northwest (300-330 degree) swell energy are expected to come across from Thursday into early next week. East shore surf will subside into Wednesday as trades take a brief respite today. A fetch of stronger trades will expand east of Hawaii late Wednesday and Thursday. This will double mid week east surf heights by late Thursday. A small pulse of south southwest swell is possible today, but otherwise, mainly background level surf will prevail along southern shores.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov