Photo Credit: Braden Jarvis

West Kaua’i

Today: Mostly cloudy. Breezy. Numerous showers in the morning, then occasional showers in the afternoon. Highs around 82 near the shore to around 68 above 3000 feet. Southwest winds 10 to 20 mph. Chance of rain 80 percent.

Tonight: Mostly cloudy. Numerous showers in the evening, then scattered showers after midnight. Lows around 70 near the shore to around 60 above 3000 feet. West winds up to 15 mph. Chance of rain 70 percent.

Tuesday: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 81 near the shore to around 68 above 3000 feet. Northwest winds around 10 mph. Chance of rain 50 percent.

South Kaua’i

Today: Breezy. Mostly cloudy with numerous showers. Highs 78 to 83. Southwest winds 15 to 25 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Breezy. Numerous showers in the evening, then scattered showers after midnight. Lows around 68. West winds 10 to 25 mph decreasing to 10 to 15 mph after midnight. Chance of rain 60 percent.

Tuesday: Partly sunny with scattered showers. Highs 78 to 83. Northwest winds around 10 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Breezy. Mostly cloudy with numerous showers. Highs 74 to 80 in the valleys to around 62 above 4000 feet. Southwest winds 10 to 25 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Breezy. Numerous showers in the evening, then scattered showers after midnight. Lows 61 to 68 in the valleys to around 58 above 4000 feet. Southwest winds 10 to 25 mph becoming west after midnight. Chance of rain 70 percent.

Tuesday: Partly sunny with scattered showers. Highs 72 to 77 in the valleys to around 62 above 4000 feet. Northwest winds 10 to 15 mph. Chance of rain 50 percent.

North Kaua’i

Today: Breezy. Mostly cloudy with scattered showers. Highs 72 to 83. Southwest winds 10 to 25 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Breezy. Numerous showers in the evening, then scattered showers after midnight. Lows 63 to 70. Southwest winds 10 to 20 mph. Chance of rain 70 percent.

Tuesday: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 71 to 80. Northwest winds around 10 mph. Chance of rain 50 percent.

East Kaua’i

Today: Mostly cloudy. Windy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 72 to 82. Southwest winds 10 to 30 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Breezy. Numerous showers in the evening, then scattered showers after midnight. Lows 63 to 73. Southwest winds 10 to 25 mph shifting to the west 10 to 15 mph after midnight. Chance of rain 70 percent.

Tuesday: Partly sunny with scattered showers. Highs 72 to 81. Northwest winds around 10 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

A front will move down the island chain through Wednesday, bringing breezy southwesterly winds and rain. A second front will sweep through the islands Thursday night and Friday, introducing another round of rain. Trade winds will return and become strong behind this second front.

Discussion

A front near Kauai is moving slowly eastward and is poised to move across that island within the next few hours. Satellite loop shows a broad but ragged band of low clouds associated with this front extending about 200 miles westward from Kauai. A prefrontal cloud band across Oahu is about to move northeast and away this morning. Southwest winds ahead of the front are locally breezy across the state. Lighter southwest winds and clearer skies persist across Maui and the Big Island. Westerly winds aloft were beginning to decrease, but began to increase again after midnight and remain above warning threshold at this hour. As a result, the High Wind Warning for the Big Island summits has been extended through 6 pm HST this evening.
Models show the front will reach Kauai later this morning, along with increased showers and strengthening southwest winds. Prefrontal showery low clouds may affect Kauai earlier than that. The front will slowly move eastward down the island chain, impacting Oahu and Maui County tonight and Tuesday, then weaken near the Big Island Wednesday into Thursday. Southwest wind gusts up to 45 mph are possible along north and east sides of the islands due to downslope effects, mainly across Kauai and Oahu this afternoon and evening. This is just below advisory threshold. The front will not be quite as strong when it reaches Maui County and the Big Island, so downslope gusts will be somewhat weaker. Expect drier and more stable conditions, along with light north to northeast winds, behind the front.
As the front is dissipating across the Big Island Thursday, another front will approach the main Hawaiian Islands from the northwest. Expect this next front to quickly move across the island chain Thursday night into Friday, with strong trade winds building behind. Winds will easily exceed advisory levels for most of the state in the wake of this next front late Friday into Saturday. Expect a quick bout of rainfall as this next front passes through.

Aviation

Moderate to breezy southwest winds will continue through tonight. A cold front just northwest of the islands will move across Kauai this morning then gradually progress down the island chain through the middle of the week. Expect clouds and showers to increase across western islands today, with widespread MVFR cigs and vsbys along with breezy to windy conditions likely as the front moves eastward.
AIRMET Tango for moderate turbulence below 8000 ft remains in effect for north through east sections of all islands, with conditions continuing through tonight. AIRMET Sierra for mountain obscuration above 2000 ft is in effect for areas west of Molokai.

Marine

Fresh to strong SW winds will continue through tonight as a front approaches. This combined with the arrival of a WNW swell tonight has led to the Small Craft Advisory being expanded down the island chain for exposed waters due to a combination of winds and seas. The winds will quickly ease as the front advances down the island chain and stalls over the eastern end of the state tonight through Tuesday night, likely enough for localized land and sea breeze conditions to form near the coasts (light N background flow trailing the front Tuesday into Tuesday night). Light to moderate E background flow is forecast for a brief period Wednesday as the next front approaches. This next front will move through Thursday through Friday with strong N winds trailing the front Thursday night through Friday. Strong trades are depicted over the weekend as high pressure builds north of the area.
Surf along exposed N and W facing shores will remain rough into tonight due to a mix of building short-period wind waves associated with the increasing SW winds and the arrival of a medium period WNW swell. Surf heights will near advisory levels for N and W facing shores of the smaller islands today. A larger WNW swell arriving tonight into Tuesday will drive the surf to near warning levels Tuesday through Tuesday night as it peaks. Similar to other recent WNW swells during the last few weeks, surf along the leeward side of the Big Island will likely near their warning level Tuesday through Tuesday night.
As this WNW swell eases Wednesday through Thursday, guidance shows a mix of a moderate N to NNE and WNW swell moving through. The NNE component will become the dominant swell Thursday night through Friday in response to a broad gale forming in the northeast Pacific Tuesday through midweek – likely enough for a return to advisory-level surf for exposed coasts (010-020 deg swell).
Surf along E facing shores will remain small through most of the week due to the lack of trades locally and upstream. An upward trend is expected later in the week through next weekend as the large NNE swell and strong trades return.
Surf along S facing shores will remain rough through tonight due to strengthening southwest winds. A downward trend is expected Tuesday through midweek as winds diminish.

HFO Watches/Warnings/Advisories

High Wind Warning until 6 PM HST today for Big Island Summits.
Small Craft Advisory until 6 PM HST Tuesday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters.

Data Courtesy of NOAA.gov