Photo Credit: Braden Jarvis

West Kaua’i

Today: Breezy. Mostly sunny with isolated showers. Highs around 81 near the shore to around 70 above 3000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Tonight: Breezy. Partly cloudy with isolated showers. Lows 64 to 69 near the shore to around 56 above 3000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Sunday: Breezy. Mostly sunny with isolated showers. Highs around 81 near the shore to around 70 above 3000 feet. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 20 percent.

South Kaua’i

Today: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs 77 to 82. Northeast winds 20 to 25 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with showers likely. Lows around 66. Northeast winds 15 to 25 mph. Chance of rain 70 percent.

Sunday: Partly sunny. Breezy. Showers likely in the morning, then scattered showers in the afternoon. Highs 77 to 82. Northeast winds 15 to 25 mph. Chance of rain 70 percent.

Kaua’i Mountains

Today: Windy. Partly sunny with showers. Highs 69 to 76 in the valleys to around 60 above 4000 feet. East winds 10 to 30 mph. Chance of rain 80 percent.

Tonight: Windy. Cloudy with showers. Lows 57 to 65 in the valleys to around 54 above 4000 feet. East winds 10 to 30 mph decreasing to up to 25 mph after midnight. Chance of rain 90 percent.

Sunday: Cloudy and breezy. Showers in the morning, then scattered showers in the afternoon. Highs 68 to 74 in the valleys to around 60 above 4000 feet. East winds up to 25 mph increasing to 10 to 25 mph in the afternoon. Chance of rain 90 percent.

North Kaua’i

Today: Breezy. Partly sunny with showers likely. Highs 71 to 81. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 70 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 58 to 68. East winds up to 20 mph. Chance of rain 50 percent.

Sunday: Breezy. Partly sunny with scattered showers. Highs 70 to 81. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

East Kaua’i

Today: Breezy. Partly sunny with showers likely. Highs 69 to 80. Northeast winds 10 to 20 mph. Chance of rain 70 percent.

Tonight: Breezy. Mostly cloudy with showers likely. Lows 59 to 71. Northeast winds 10 to 20 mph. Chance of rain 70 percent.

Sunday: Mostly cloudy. Breezy. Showers likely in the morning, then scattered showers in the afternoon. Highs 68 to 80. Northeast winds 10 to 20 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

Trade winds will weaken slightly but will nonetheless remain strong and gusty through the weekend before weakening slightly early next week. A wetter trade wind pattern will develop over the eastern end of the state this weekend and potentially spread to the remaining islands early next week.

Discussion

Observational trends during the last several hours and the latest guidance offer strong support for allowing the wind advisory to expire on schedule for Oahu and Kauai. Trades will nonetheless remain strong and gusty through the weekend, but the potential for higher end gusts statewide is decreasing as the inversion weakens and winds in the 2-5kft layer rapidly diminish. The advisory has been extended through this evening for Maui County and the Big Island where local accelerations in the typical windier zones should be enough in the presence of strong background winds to generate sustained winds up to 30 mph and gusts up to 50 mph.
Locally strong trades will continue through the weekend, tending to gradually weaken as a mid-level low positioned to the southeast lifts northward and becomes established over the islands. Subsequent weakening of the inversion and modest pressure falls will take the edge off of the trades by Sunday into early next week. A typical trade wind shower pattern will manifest through this time as showers focus mainly over windward and mauka zones.
Global models maintain a firm consensus that a split flow pattern will continue well into next week. Mid-level ridging over northeast Pacific will persist in maintenance of a trade wind pattern across the islands. At the same time, the closed low over the islands will receive a steady influx of cyclonic reinforcement and cooler air aloft by the southern branch of the jet as it wraps around the southern periphery of the low. The inversion will gradually weaken as stability wanes and moisture deepens, especially over the eastern end of the state. A wetter pattern will evolve over Windward Big Island and portions of of Maui County as showers increase in coverage. A few locally heavy showers will be possible, but support for prolonged periods of intense rain rates appears quite limited at this time. The notable exception will be within any thunderstorms that develop, most likely over the leeward slopes of the Big Island. Isolated thunderstorms are expected by Sunday afternoon and may remain a possibility into the middle of next week. As the upper low shifts westward early next week wetter trade wind weather will spread to the remaining islands.

Aviation

A strong high pressure system north to northeast of the Hawaiian Islands will continue to produce strong and gusty trade winds across the region today. Strong winds will slowly weaken into the breezy range by Sunday. An unstable upper level low will keep periods of showers in the forecast through the weekend with the highest shower coverage expected over windward and mountain slopes during the overnight to early morning hours. Mostly VFR conditions are forecast for most airfields with brief periods of MVFR conditions in showers for airfields along north and east slopes of all islands.
AIRMET Tango remains in effect for sustained surface winds of 30 kt or greater. AIRMET Tango also remains in effect for low level moderate to isolated severe turbulence over and downwind of all island mountains. There have been several PIREP's overnight that verified the moderate to severe low level turbulence near southern Maui. This AIRMET for low level turbulence will likely continue through this evening, while the strong surface wind AIRMET will drop later today as the wind speeds weaken.

Marine

Very strong easterly trades will continue through the weekend, with Gale force winds expected in the windier channels through 6 pm this evening. Elsewhere, Small Craft Advisories will remain in place due to a combination of winds and elevated seas. The trades will ease a bit Sunday through early next week, however, Small Craft Advisories will likely be needed for most marine zones through the middle of next week due to winds/seas or a combination of the two.
Surf along east facing shores will remain very rough through the weekend, with only slight improvement expected early next week as the trade winds ease a bit over and upstream of the islands. Dangerous, warning-level surf is expected to continue along east facing shores today. Large breaking waves, especially along the rockier coastlines, should be expected. Additional hazards such as beach erosion, powerful rip/alongshore currents, and occasional overwash onto vulnerable roadways can be expected as well. Surf along east facing shores should lower a bit tonight through the middle of next week, but will likely remain at or near advisory levels during this time.
The current north swell will subside through the weekend. A long period northwest swell will build Sunday and peak Sunday night into Monday near or just below advisory levels along north and west facing shores. This swell will decline Monday night and Tuesday, with a new long period northwest swell building Wednesday and peaking below advisory levels Wednesday night into Thursday, then gradually lowering Thursday night into next weekend.

HFO Watches/Warnings/Advisories

Wind Advisory until 6 PM HST this evening for Maui County and portions of the Big Island.
High Surf Warning until 6 PM HST this evening for Olomana, Maui Windward West, Kauai East, Koolau Windward, Molokai Windward, Molokai North, Maui Central Valley North, Windward Haleakala, Big Island East, Big Island North.
Small Craft Advisory until 6 PM HST this evening for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Oahu Leeward Waters, Maui County Windward Waters, Maui County Leeward Waters, Big Island Windward Waters.
Gale Warning until 6 PM HST this evening for Kaiwi Channel, Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov