Photo Credit: Brendan Stephen

West Kaua’i

Today: Partly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 86 near the shore to around 74 above 3000 feet. East winds up to 10 mph shifting to the south in the afternoon. Chance of rain 40 percent.

Tonight: Partly cloudy with isolated showers. Lows around 71 near the shore to around 61 above 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Thursday: Partly sunny with isolated showers. Highs around 86 near the shore to around 73 above 3000 feet. East winds around 10 mph. Chance of rain 20 percent.

South Kaua’i

Today: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 80 to 86. East winds 10 to 15 mph. Chance of rain 30 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 72. East winds 10 to 15 mph. Chance of rain 50 percent.

Thursday: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 78 to 85. East winds 10 to 15 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Mostly cloudy with scattered showers. Highs 75 to 81 in the valleys to around 67 above 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then showers likely after midnight. Lows 65 to 70 in the valleys to around 59 above 4000 feet. East winds up to 15 mph. Chance of rain 70 percent.

Thursday: Mostly cloudy. Showers likely in the morning, then scattered showers in the afternoon. Highs 72 to 80 in the valleys to around 64 above 4000 feet. East winds 10 to 15 mph. Chance of rain 70 percent.

North Kaua’i

Today: Mostly cloudy. Isolated showers in the morning, then scattered showers in the afternoon. Highs 77 to 87. Southeast winds up to 15 mph. Chance of rain 40 percent.

Tonight: Mostly cloudy with scattered showers. Lows 65 to 73. Southeast winds up to 15 mph. Chance of rain 50 percent.

Thursday: Partly sunny with scattered showers. Highs 76 to 86. East winds 10 to 15 mph. Chance of rain 50 percent.

East Kaua’i

Today: Mostly cloudy with scattered showers. Highs 73 to 84. East winds up to 10 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 65 to 75. East winds up to 15 mph. Chance of rain 50 percent.

Thursday: Mostly cloudy with scattered showers. Highs 71 to 82. East winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Moderate to locally breezy trade winds will continue over the eastern islands. Lighter east-southeast winds will prevail over the western end of the state which will allow for localized land and sea breezes over mainly Oahu and Kauai. Clouds and showers will generally favor windward and mauka areas, with a few showers developing over interior and leeward sections of Oahu and Kauai this afternoon and evening. Moderate to breezy easterly trade winds will then spread over the state tonight into Thursday and linger through the first half of next week, with showers favoring typical windward and mauka areas.

Discussion

The latest surface analysis shows a trough of low pressure around 350 miles west-northwest of Kauai, with a 1036 mb high centered around 1600 miles north-northeast of Honolulu. Satellite imagery shows a mix of low and high clouds across the state early this morning, with low clouds and a few showers favoring windward and mauka areas. Moderate to locally breezy trade winds prevail over the eastern islands, with light to moderate east-southeast winds over Oahu and Kauai. Expect this pattern to continue through this evening, with clouds and showers over typical windward and mauka areas. Meanwhile, lighter winds over Oahu and Kauai will allow for localized leeward sea breezes and isolated showers for most sheltered areas this afternoon and evening.
Guidance continues to show the trough slowly shifting westward today, but despite its proximity to the islands the heaviest rainfall will remain west of Hawaii. Meanwhile, high pressure will slowly shift north of the state later today, and a series of reinforcing highs will build to our north through the first half of next week. This will allow trade winds to strengthen across the region, with moderate to breezy easterly trade winds expected statewide by Thursday and continuing into much of next week. Guidance also shows drier air filtering into the region over the coming days. This will allow a more stable trade wind pattern to develop. Expect windward and mauka showers to increase in intensity and coverage during the overnight and early morning hours, with a few of these showers briefly spilling over into leeward areas. This pattern should hold through the first half of next week.

Aviation

A moderate east to southeast flow will persist into Thursday with a high pressure system to the northeast of the region. An area of moisture remains over the eastern sides of the Big Island and Maui overnight, bringing MVFR and pockets of IFR conditions to those areas. Conditions have shown some improvements over the eastern side of the Big Island in the last few hours, however satellite shows additional clouds upstream that will be coming in a couple of hours. AIRMET Sierra for mountain obscuration remains in effect for these parts of Maui and the Big Island, and expecting that to remain in place, possibly into tonight.
Windward clouds and showers have increased slightly, and may increase some more over the next few hours. This will bring some brief MVFR conditions to the remaining islands, but VFR are expected to prevail.

Marine

Strong high pressure far northeast of the state is driving fresh to strong easterly trade winds around the Big Island and Maui, and a surface trough northwest of Kauai is causing winds to shift out of the east-southeast over Oahu and Kauai. A Small Craft Advisory (SCA) was extended through Thursday afternoon for all waters around the Big Island, waters north of Maui, and the Pailolo Channel. As the trough weakens and drifts westward, expect the stronger easterly trades winds to spread to Oahu and Kauai, with the SCA likely adjusted to cover the typically windy waters around the Big Island and Maui County. Moderate to strong easterly trade winds will persist into the weekend.
The south swell will continue to decline over south and exposed west shores today. Only small long period background south swell pulses are expected from Tasman Sea sources into the first half of next week. The next long period south swell burst may reach island shores by next week Friday May 31st.
Rough surf along east facing shores will slowly rise over the next few days as the trades strengthen upstream of the state. Surf heights along north and west facing shores will remain small with a slight bump up from Sunday into Monday.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Thursday for Maui County Windward Waters, Pailolo Channel, Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov