Photo Credit: Sebastien Gabriel

West Kaua’i

Today: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 79 near the shore to around 67 above 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly clear. Lows around 66 near the shore to around 55 above 3000 feet. East winds 10 to 15 mph.

Sunday: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs around 79 near the shore to around 67 above 3000 feet. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

South Kaua’i

Today: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs around 78. Northeast winds 15 to 20 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 62 to 67. Northeast winds 15 to 20 mph. Chance of rain 40 percent.

Sunday: Partly sunny with scattered showers. Highs around 78. Northeast winds around 15 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Breezy. Partly sunny with scattered showers. Highs 66 to 74 in the valleys to around 61 above 4000 feet. East winds 15 to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows 55 to 60 in the valleys to around 49 above 4000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Sunday: Breezy. Occasional showers in the morning, then numerous showers in the afternoon. Highs 66 to 74 in the valleys to around 61 above 4000 feet. East winds 15 to 20 mph. Chance of rain near 100 percent.

North Kaua’i

Today: Partly sunny with scattered showers. Highs 71 to 78. East winds around 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 58 to 67. East winds 10 to 15 mph. Chance of rain 50 percent.

Sunday: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs 71 to 78. East winds 10 to 15 mph. Chance of rain 70 percent.

East Kaua’i

Today: Partly sunny with scattered showers. Highs 71 to 78. East winds around 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 56 to 68. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Sunday: Mostly cloudy with scattered showers. Highs 71 to 78. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

High pressure far north of the main Hawaiian Islands will keep breezy trades blowing through the weekend. Trade winds will weaken on Sunday as the high moves away. By Sunday, an upper trough developing over the islands generate more frequent trade wind showers, a trend which will last through much of next week. A new high forecast to build north of the islands will increase trades to locally windy levels by Tuesday.

Discussion

A high far north of the main Hawaiian Islands continues to drive breezy to locally windy trade winds over the islands this morning. Overnight soundings show our airmass is relatively dry, with PW between 0.9 and to 1.2 inches. Satellite loop shows an upper low far northeast of the Big Island, with an associated upper trough extending southwest over waters just east of the state. As the low and upper trough move east and away from the islands, expect weak upper ridging and brief warming aloft. This should make for a pretty nice day today across the state. Showers should be limited and relatively light, with considerable sunshine for most areas.
An upper trough will dig over the islands late tonight into Sunday, then linger for much of next week. Instability will increase as cold air builds in aloft. At the same time, trades winds will weaken a bit as the high moves away. Winds will restrengthen, back to at least locally windy levels, as another high passes north of the islands early next week. The northern fringes of an area of deeper moisture to the east and southeast of the Big Island will approach the Big Island on Sunday and linger into the first half of the week.
Expect wetter trade wind weather early next week, with two time periods of higher confidence for heavier downpours and possible thunderstorms. One is over the windward side of the Big Island Sunday night into Monday as deeper moisture moves in. The next is Monday night into Tuesday, mainly near Kauai, as cold temperatures aloft and airmass instability associated with upper troughing move in from the northwest. There is a chance of wintry weather at the summits of Mauna Loa, Mauna Kea, and possibly even Haleakala. Models show the upper trough will linger into the latter half of the week. Low level moisture will gradually decrease and the subtropical jet streak will shift east and away from the state. This should lead to a gradual decrease in trade wind shower intensity and coverage.

Aviation

VFR conditions will prevail with breezy trade winds bringing occasional MVFR clouds and showers to windward and mauka areas. Low clouds remain anchored over windward Oahu this morning so AIRMET Sierra for tempo mountain obscuration remains posted. May need to extend AIRMET Sierra to other windward slopes as another plume of moisture moves through.
AIRMET Tango for moderate lee turbulence remains in effect across all islands.

Marine

Winds will briefly ease from Sunday into Monday as the high north of the state weakens and drifts southeastward. Otherwise moderate to locally strong trade winds to continue for most days into next week as two additional high pressure systems pass by just north of Hawaii. A Small Craft Advisory (SCA) is posted for the typically windy waters around the Big Island and Maui through tonight, with borderline conditions expected on Sunday. The SCA will likely be needed for all waters late Monday or by Tuesday.
Small to moderate swells from around the compass will continue into early next week. A small north-northeast swell will continue today, and a reinforcing moderate pulse is expected by tonight and Sunday, followed by a decline from Monday to Tuesday. Though the bulk of this swell energy will pass east of Hawaii, we will need to monitor local buoys, as a larger than expected swell may pose a risk of harbor surges at Hilo and Kahului. Meanwhile, a small northwest swell will build this weekend and produce surf near the High Surf Advisory levels from Sunday night to Monday, before declining through the remainder of next week.
A small, out of season south swell will hold today and then slowly decline on Sunday and Monday. Moderate trade wind swell will persist near seasonal average today and will ease slightly on Sunday before rebuilding early next week.

HFO Watches/Warnings/Advisories

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

Data Courtesy of NOAA.gov