Photo Credit: Sebastien Gabriel

West Kaua’i

Today: Partly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 85 near the shore to around 73 above 3000 feet. Southeast winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with isolated showers. Lows 67 to 72 near the shore to around 58 above 3000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Wednesday: Partly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 85 near the shore to around 73 above 3000 feet. East winds up to 15 mph. Chance of rain 40 percent.

South Kaua’i

Today: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 82. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 65 to 71. East winds 10 to 15 mph. Chance of rain 30 percent.

Wednesday: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 82. East winds 10 to 15 mph. Chance of rain 30 percent.

Kaua’i Mountains

Today: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 72 to 79 in the valleys to around 63 above 4000 feet. East winds up to 10 mph. Chance of rain 60 percent.

Tonight: Mostly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 58 to 63 in the valleys to around 53 above 4000 feet. East winds up to 10 mph. Chance of rain 30 percent.

Wednesday: Mostly cloudy with scattered showers. Highs 72 to 79 in the valleys to around 63 above 4000 feet. East winds up to 15 mph. Chance of rain 40 percent.

North Kaua’i

Today: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 75 to 84. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with isolated showers. Lows 61 to 71. Southeast winds up to 15 mph. Chance of rain 20 percent.

Wednesday: Mostly cloudy. Isolated showers in the morning, then scattered showers in the afternoon. Highs 75 to 84. East winds up to 15 mph. Chance of rain 40 percent.

East Kaua’i

Today: Mostly cloudy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 75 to 83. East winds around 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 59 to 72. East winds 10 to 15 mph. Chance of rain 30 percent.

Wednesday: Mostly cloudy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 75 to 83. East winds 10 to 15 mph. Chance of rain 40 percent.

Detailed Forecast

Synopsis

Moderate to locally breezy trades will hold over the eastern islands during the next couple days, while lighter trades allow for some localized land and sea breezes over the western end of the state. Showers will favor windward and mauka areas overnight and during the morning hours, with a few showers developing over interior and leeward sections each afternoon and evening. A more typical moderate to breezy trade wind pattern will overspread the state Wednesday night or Thursday and linger through early next week, with showers favoring windward and mauka areas, along with the occasional leeward spillover.

Discussion

Currently at the surface, a trough of low pressure is located around 300 miles west-northwest of Kauai, while a 1035 mb high is centered around 1600 miles north-northeast of Honolulu. Moderate to locally breezy trade winds prevail over the eastern islands, while light to moderate trades remain over the western end of the state. Infrared satellite imagery shows a mix of high and low clouds bringing mostly cloudy conditions to the state this morning. Radar imagery shows relatively dry conditions across the state, with only a few showers moving into windward areas. Main short term focus revolves around rain chances and trade wind trends during the next couple days.
The trough to the west-northwest of the state will gradually shift westward and further away from the islands during the next couple days. This will allow the trade winds to gradually strengthen from east to west across the islands, with moderate to breezy conditions expected statewide by Thursday. The gradient will likely be light enough today and Wednesday, to allow some localized leeward sea breezes in the most sheltered areas over Kauai and Oahu. A series of reinforcing highs will build north of the state Friday through early next week, while the trough continues to shift further west and away from the area. This will maintain moderate to breezy trade winds across the island chain.
As for the remaining weather details, fairly dry conditions should prevail this morning, with light showers limited mainly to windward slopes and coasts. A band of moisture appears to move in from the east this afternoon, bringing an increase in trade wind showers to the eastern end of the state. Additionally, a few leeward and interior showers will be possible over the western islands and leeward Big Island during the afternoon. Showers should diminish quickly over leeward areas this evening, with showers focusing over windward terrain tonight into Wednesday morning. Localized sea breezes may then allow for some leeward shower development again Wednesday afternoon. Beginning Wednesday night or Thursday, we should see a transition over to a more typical trade wind pattern featuring mainly windward/mauka showers and the occasional leeward spillover, with showers most prevalent in the overnight and early morning hours. This pattern should hold through early next week.

Aviation

Light to moderate east to southeast winds will persist through the 24-Hr forecast period. Despite the lack of windward showers, MVFR CIGs associated with a stable low cloud deck will remain possible through the early morning hours over the eastern end of the state. A few leeward showers are possible this afternoon where localized sea breezes form. Otherwise, VFR conditions will prevail.
AIRMET Sierra is in effect for mountain obscuration over the windward slopes of the Big Island and Maui. Conditions should improve through the mid- to late-morning hours.

Marine

An area of low pressure west to northwest of the state will slowly drift westward away from the islands through much of this week. High pressure will slowly build into the Hawaii region with a slight strengthening of easterly trade winds as this low pressure trough moves away from the state. Expect fresh to locally strong easterly trade winds over the eastern waters and gentle to fresh east-southeast winds over western waters today. Easterly trade winds will strengthen over the western waters from Thursday onward. A Small Craft Advisory (SCA) remains in effect for the windier coastal waters around Maui County and the Big Island through Wednesday. The SCA will likely continue for some of these eastern windier waters through the end of the week.
Surf along south-facing shores will continue to gradually decline over the next few days. Only small long period background south swell pulses are expected from Tasman Sea sources over the next seven days. Surf along east facing shores should see a gradual 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 Wednesday for Maui County Windward Waters, Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov