Photo Credit: Brendan Stephen

West Kaua’i

Today: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs around 87 near the shore to around 75 above 3000 feet. Northeast winds up to 10 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows around 72 near the shore to around 60 above 3000 feet. Northeast winds up to 10 mph. Chance of rain 40 percent.

Sunday: Mostly sunny with isolated showers. Highs around 86 near the shore to around 74 above 3000 feet. East winds up to 10 mph. Chance of rain 20 percent.

South Kaua’i

Today: Partly sunny. Showers likely in the morning, then scattered showers in the afternoon. Highs around 84. Northeast winds around 10 mph. Chance of rain 60 percent.

Tonight: Mostly cloudy with scattered showers. Lows 68 to 73. Northeast winds around 10 mph. Chance of rain 50 percent.

Sunday: Partly sunny with scattered showers. Highs around 83. Northeast winds around 10 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Mostly cloudy. Showers likely in the morning, then scattered showers in the afternoon. Highs 74 to 81 in the valleys to around 65 above 4000 feet. East winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Showers likely in the evening, then scattered showers after midnight. Lows 60 to 65 in the valleys to around 55 above 4000 feet. East winds 10 to 15 mph. Chance of rain 70 percent.

Sunday: Partly sunny with scattered showers. Highs 73 to 80 in the valleys to around 64 above 4000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

North Kaua’i

Today: Partly sunny. Showers likely in the morning, then scattered showers in the afternoon. Highs 77 to 86. East winds up to 10 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with scattered showers. Lows 63 to 72. East winds around 10 mph. Chance of rain 50 percent.

Sunday: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 76 to 85. East winds up to 10 mph. Chance of rain 50 percent.

East Kaua’i

Today: Mostly cloudy. Showers likely in the morning, then scattered showers in the afternoon. Highs 77 to 85. East winds around 10 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with scattered showers. Lows 61 to 75. East winds around 10 mph. Chance of rain 50 percent.

Sunday: Partly sunny with scattered showers. Highs 76 to 84. East winds around 10 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Moderate trade winds remain in the forecast through Monday. An upper level low just east of the Big Island will slowly drift northward over the next few days keeping unstable conditions around with scattered to numerous shower activity over windward and mountain areas through tonight. The transition to drier conditions will start on Sunday and Monday. A strong high pressure system building in from the north early next week will bring moderate to breezy trade winds from Tuesday onward with more stable weather trends across the state lasting through Thursday. Another round of wet weather may develop by the end of next week.

Discussion

The large scale weather pattern remains unchanged with a weak low pressure system lingering just east of the Big Island within a larger upper level trough over the state. This upper level low and trough feature will continue to produce wet weather over the islands for one more day. Isolated thunderstorms are forecast for the Big Island slopes this afternoon. A large band of cirrus clouds remains in the satellite imagery, south through east of the state, outlining the subtropical jet stream.
The high pressure ridge north of the islands will remain on the weaker side with moderate trade winds in the forecast through Monday. The upper level low just east of the islands will slowly drift north. The trade wind inversion heights will remain elevated over the region producing scattered to numerous showers through tonight. These showers will favor the typical windward and mountain areas, especially in the overnight to early morning hours. Some of the stronger showers will briefly pass over leeward areas in this unstable environment.
A gradual transition to more stable conditions will start over the on Sunday and Monday as the upper low lifts northward and a strong high pressure system at the surface builds in from the north. This high pressure ridge building into the islands from Tuesday through Thursday will allow the trade winds to strengthen into the moderate to breezy range.
Long range forecast guidance tool are beginning to suggest that Hawaiian weather conditions will trend back towards the wet side from Friday into next Saturday, as colder air aloft associated with a weak upper level trough may destabilize the regional environment. For now we are going with more a more normal (climatological) trade wind weather pattern over the islands. However, stay tuned, as we may trend the forecast towards more rainfall late next week.

Aviation

High pressure north of the area will maintain moderate trade winds across the state. VFR conditions prevail at all TAF sites and these conditions are expected to continue today. Expect brief periods of MVFR conditions over windward slopes as moisture embedded in the trades interacts with island terrain. Expect thunderstorms at times across interior areas of the Big Island this afternoon.
AIRMET Tango remains in effect over Maui and the Big Island, including the adjacent coastal waters, between FL200 and FL400 due to TEMPO moderate turbulence. No other AIRMETS are in effect now, and none are anticipated through today.

Marine

A surface ridge far northeast of the state will remain relatively weak through Sunday. An upper-level low will disrupt the pressure gradient across the eastern end of the state. As a result, moderate to locally fresh trade winds will prevail, and no Small Craft Advisory (SCA) conditions are expected this weekend. The trade winds will gradually strengthen early next week as a new surface high pressure system builds far north-northeast of the state. The latest forecast indicates SCA conditions may return over the typically windier waters adjacent to the islands of Maui County and the Big Island starting Tuesday.
Surf along north and west facing shores will remain below the seasonal average into early next week. The current small, short- period north swell will continue to fade this weekend, followed by a small, medium-period north-northwest swell arriving early Monday. The current south-southwest swell will continue into early next week, followed by overlapping pulses of new south- southwest swell energy spreading over the area from Tuesday through the end of next week. This will cause surf along south facing shores to be near, or above the seasonal average for much of next week. Surf along east facing shores will decline later this weekend due to the weak trade winds near the state. As the trade winds strengthen early next week, rough surf along east facing shores will gradually build, and possibly be above the seasonal average by late in the week.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov