Photo Credit: Brendan Stephen

West Kaua’i

Today: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs around 84 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 50 percent.

Tonight: Partly cloudy with scattered showers. Lows 67 to 72 near the shore to around 58 above 3000 feet. Light winds becoming northeast up to 10 mph after midnight. Chance of rain 50 percent.

Monday: Mostly sunny with scattered showers in the morning, then partly sunny with isolated showers in the afternoon. Highs around 84 near the shore to around 74 above 3000 feet. Northeast winds up to 10 mph shifting to the southeast in the afternoon. Chance of rain 30 percent.

South Kaua’i

Today: Partly sunny with numerous showers in the morning, then mostly sunny with scattered showers in the afternoon. Highs around 82. Southeast winds around 10 mph. Chance of rain 70 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows 65 to 71. Northeast winds around 10 mph. Chance of rain 40 percent.

Monday: Partly sunny with scattered showers in the morning, then mostly sunny with 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 with numerous showers. Highs around 77 in the valleys to around 66 above 4000 feet. Southeast winds up to 10 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Numerous showers early in the evening, then scattered showers in the late evening and overnight. Lows around 61 in the valleys to around 53 above 4000 feet. Light winds becoming east up to 10 mph after midnight. Chance of rain 70 percent.

Monday: Partly sunny with scattered showers. Highs around 77 in the valleys to around 66 above 4000 feet. East winds up to 10 mph. Chance of rain 40 percent.

North Kaua’i

Today: Partly sunny with scattered showers. Highs 77 to 83. East winds up to 10 mph. Chance of rain 50 percent.

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

Monday: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 77 to 83. East winds up to 15 mph. Chance of rain 40 percent.

East Kaua’i

Today: Mostly cloudy with numerous showers in the morning, then mostly sunny with scattered showers in the afternoon. Highs 75 to 81. Southeast winds up to 10 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with scattered showers. Lows 59 to 72. East winds up to 10 mph. Chance of rain 50 percent.

Monday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 75 to 81. East winds up to 10 mph. Chance of rain 40 percent.

Detailed Forecast

Synopsis

Moderate trades will prevail over the eastern islands through the first half of the work week, while lighter trades over the western islands allow for some leeward land and sea breezes. A plume of moisture will keep some showery weather over Kauai today, while drier conditions overspread the remainder of the state. The rather dry weather will persist through Tuesday, with a few showers possible over interior and leeward areas each afternoon, while showers will remain limited to mainly windward areas at night. The trades will rebound Tuesday night and Wednesday, bringing a return of more typical trade wind weather. The trades will become breezy Thursday through next weekend, and the trade wind showers may increase as well due to a disturbance aloft moving over the islands.

Discussion

Currently at the surface, a front is located around 550 miles west-northwest of Kauai, while a 1029 mb high is centered around 1350 miles northeast of Honolulu. Moderate trade winds prevail in unsheltered areas over the eastern end of the state, while light to moderate trades persist over the western islands. Infrared satellite imagery shows partly to mostly cloudy conditions across the state. Radar imagery shows scattered showers moving into windward slopes and coasts, with a few showers also in leeward areas of Kauai and Oahu. Main short term focus revolves around trade wind trends and rain chances during the next few days.
A front northwest of the state will gradually weaken into a trough during the next few days as it edges slowly eastward. A slight easing of the trades can be expected as we head into the first couple days of the upcoming work week. Overall, moderate trades look to hold on over the eastern islands, while lighter trades prevail over the western islands, allowing some leeward sea and land breezes to develop. We should see the trades start to rebound beginning Tuesday night as the trough west of the state begins to shift westward. Moderate to locally breezy trades should overspread the state by late Wednesday, with the trades becoming breezy across the entire island chain Thursday through next weekend.
As for the remaining weather details, the band of moisture which brought rather showery weather to most windward areas overnight is in the process of breaking up as drier air works in from the east and mid-level ridging begins to build overhead. Scattered showers will continue to affect windward areas early this morning, with shower activity then limited to primarily leeward and interior areas this afternoon. A more showery pattern is expected across Kauai today as the band of enhanced moisture will be slower to exit here.
From tonight through Tuesday, relatively dry conditions should prevail across the island chain. Brief passing showers will be possible in windward areas each night, with a few showers developing over interior and leeward areas each afternoon. We should see a return to more typical trade wind weather Tuesday night and Wednesday, with wetter trade wind weather potentially developing Friday through next weekend as upper troughing sets up over the state.

Aviation

Moisture riding in on the light to moderate ESE trades will continue to provide a steady supply of showers to windward and mauka areas of the Hawaiian Islands through the morning hours, with tempo MVFR conditions expected within heavier showers. With a SE element to the winds, showers will occasionally be steered across leeward areas as well.
Drier air will move in from the east later today, allowing conditions to improve across most of the state, but moisture will linger across Kauai through the period. With the lighter flow and decreased cloud cover, sea breeze activity will be possible across protected areas mainly during the afternoon hours.
AIRMET Sierra for mountain obscuration is in effect for portions of the Big Island and Molokai through Kauai. This AIRMET will likely be needed through the morning hours before conditions begin to improve.

Marine

Surface high pressure centered roughly 1200 nm northeast of the state and an approaching weak front to the northwest will drive breezy east southeast winds today, especially across all windward waters and through the channels surrounding Maui County and the Big Island. Through early this week, the aforementioned surface high will drift eastward and allow flow to weaken. By mid-week, high pressure will rebuild to the north and allow easterly flow to strengthen again.
A Small Craft Advisory for winds will remain in effect for most waters and channels surrounding Big Island, Maui, and Molokai through Monday morning, then likely be dropped as winds weaken.
Surf heights will remain below advisory thresholds for all shores through the forecast period. A small northwest, medium-period swell will persist through mid-week with small surf expected. Breezy east or east southeasterly flow will produce choppy surf along east facing shores through tonight, then decrease as winds begin to taper off early in the week. Small, short- period southeast, and small medium- period south swell will continue into mid-next week. Surf heights along the south facing shores should remain near or slightly below seasonal norms.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Monday for Maui County Windward Waters, Pailolo Channel, Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters.

Data Courtesy of NOAA.gov