West Kaua’i

Tonight: Mostly clear. Lows 68 to 73 near the shore to around 61 above 3000 feet. East winds up to 15 mph becoming around 10 mph after midnight.

Wednesday: Sunny. Isolated showers in the afternoon. Highs 84 to 90 near the shore to around 76 above 3000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Wednesday Night: Mostly clear. Lows around 71 near the shore to around 61 above 3000 feet. East winds around 10 mph.

South Kaua’i

Tonight: Breezy. Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows around 73. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Wednesday: Mostly sunny with isolated showers. Highs 80 to 89. East winds around 15 mph. Chance of rain 20 percent.

Wednesday Night: Partly cloudy with isolated showers. Lows around 72. East winds 10 to 15 mph. Chance of rain 20 percent.

Kaua’i Mountains

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then showers likely after midnight. Lows 63 to 69 in the valleys to around 59 above 4000 feet. East winds up to 20 mph becoming 10 to 15 mph after midnight. Chance of rain 70 percent.

Wednesday: Partly sunny with scattered showers. Highs 74 to 83 in the valleys to around 66 above 4000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Wednesday Night: Mostly cloudy with scattered showers. Lows 63 to 69 in the valleys to around 59 above 4000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

North Kaua’i

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows 65 to 73. East winds 10 to 15 mph. Chance of rain 50 percent.

Wednesday: Mostly sunny with isolated showers. Highs 77 to 86. East winds 10 to 15 mph. Chance of rain 20 percent.

Wednesday Night: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 65 to 73. East winds 10 to 15 mph. Chance of rain 40 percent.

East Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows 64 to 76. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Wednesday: Partly sunny in the morning then becoming mostly sunny. Isolated showers. Highs 73 to 85. East winds 10 to 15 mph. Chance of rain 20 percent.

Wednesday Night: Mostly cloudy with scattered showers. Lows 64 to 75. East winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

High pressure to the northeast of the Hawaiian Islands will remain in place and strengthen by the end of the week. Breezy trade winds and a typical windward and shower distribution can be expected with occasional pockets of showers, mainly during the night time hours. Conditions could then become drier and more windy by the weekend, followed by moderately wet trade winds next week.

Discussion

Passing showers have been observed today on radar and satellite imagery over windward and mountain areas. The sounding from this afternoon shows moderately moist air beneath a 6,000 to 8,000 ft inversion, which should support continuing trade wind showers this afternoon and tonight. Our airmass is expected to dry out by tomorrow and periodically fluctuate between periods of slightly wet and dry through the rest of the week, with showers focusing primarily over windward and mountain areas. Wind speeds appear to hold steady today before gradually decreasing a notch tomorrow through Friday into the moderate to locally breezy range. The next batch of enhanced trade wind moisture looks to arrive around Thursday night through Friday morning before drying out by Friday evening.
This weekend, high pressure northeast of the islands is forecast to strengthen, which could cause trade wind speeds to increase to breezy to strong levels. Additionally, a strong mid level ridge could move overhead along with a dry airmass. This could inhibit clouds and showers, as well as lower the relative humidity. These factors combined could increase fire risk, with a KBDI at Honolulu of 508, conditions won't quite be at red flag warning criteria, however there will still be a risk for enhanced fire weather conditions. More confidence will emerge as the weekend draws closer.
By early next week, dry conditions could be replaced by a wetter trade wind pattern as global models indicate an upper level low along with slivers of enhanced low level moisture could move in from east to west.

Aviation

Breezy trade winds with brief passing showers will continue through tonight. Wind speeds will decrease to more moderate levels from Wednesday onward. Shower activity will be limited to windward and mountain areas, favoring the overnight to early morning hours. AIRMET Sierra may be needed again for mountain obscuration for some islands again tonight if shower activity becomes widespread enough.
AIRMET Tango remains in effect for moderate turbulence over and south through west of the mountains. These stronger winds and turbulent conditions will likely continue into Wednesday.

Marine

High pressure north of Hawaii will slowly move eastward and drive fresh to strong trades across the local waters. A Small Craft Advisory (SCA) is in effect for windier waters and channels near Maui and the Big Island due to strong winds. Trade winds are forecast to strengthen this weekend.
A small, long period, south swell will arrive on Wednesday and bring a slight bump up in surf through the weeks end. Rough and choppy conditions along east facing shores will through the next week. Surf will remain nearly flat along north facing shores.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Wednesday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

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