Photo Credit: Sebastien Gabriel

West Kaua’i

Today: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs around 85 near the shore to around 71 above 3000 feet. Southeast winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows around 69 near the shore to around 58 above 3000 feet. East winds up to 10 mph in the evening becoming light. Chance of rain 50 percent.

Sunday: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 85 near the shore to around 71 above 3000 feet. Southeast winds up to 10 mph. Chance of rain 40 percent.

South Kaua’i

Today: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 77 to 84. East winds 10 to 15 mph. Chance of rain 70 percent.

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

Sunday: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 78 to 85. East winds around 10 mph. Chance of rain 40 percent.

Kaua’i Mountains

Today: Mostly cloudy. Occasional showers in the morning, then numerous showers in the afternoon. Highs 72 to 82 in the valleys to around 62 above 4000 feet. East winds up to 10 mph. Chance of rain 90 percent.

Tonight: Mostly cloudy. Numerous showers in the evening, then scattered showers after midnight. Lows around 66 in the valleys to around 56 above 4000 feet. Light winds. Chance of rain 70 percent.

Sunday: Partly sunny with scattered showers. Highs 72 to 82 in the valleys to around 63 above 4000 feet. Light winds becoming east up to 10 mph in the afternoon. Chance of rain 50 percent.

North Kaua’i

Today: Mostly cloudy with numerous showers. Highs 75 to 84. Southeast winds up to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with scattered showers. Lows 62 to 72. Southeast winds up to 15 mph. Chance of rain 50 percent.

Sunday: Partly sunny with scattered showers. Highs 75 to 85. Southeast winds up to 10 mph. Chance of rain 50 percent.

East Kaua’i

Today: Mostly cloudy. Occasional showers in the morning, then scattered showers in the afternoon. Highs 72 to 82. East winds around 10 mph becoming up to 15 mph in the afternoon. Chance of rain 90 percent.

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

Sunday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 72 to 82. East winds up to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Breezy east to east-southeast winds will continue to gradually ease through early next week. A plume of moisture will produce passing showers across windward and mountain areas through today. A drier weather pattern is expected Sunday into early next week with light to moderate east to east- southeast winds. Winds should be light enough for sea breezes to develop during the day and land breezes at night, especially early next week.

Discussion

Latest satellite and radar imagery shows scattered light to moderate showers mainly along windward and mountain areas with some showers making it to leeward zones, especially for Kauai County. Shower activity is expected trend down along windward zones. Leeward areas will see a increase in clouds and showers this afternoon as seabreezes develop. Gentle to breezy east to east-southeast winds appear to have developed over the state overnight. A ridge of high pressure north of the state will shift south today, further weakening and veering winds out of the east- southeast, especially over the western half of the state. Breezier winds will persist along windward areas and lighter winds will develop along leeward areas today as a result. A drier air mass is expected to move in by Sunday, so overall we should less showers on Sunday as well as lighter winds with sea breezes developing over many leeward areas Sunday afternoon.
For early next week, high pressure will be centered far northeast of the state, while a low pressure system shifts north of the state. We will continue to be in a hybrid wind pattern early next week with light to breezy east-southeast winds over windward areas and generally light winds over leeward areas. Due to limited moisture, we are not expecting much rainfall early next week, but some light passing showers should be expected over windward areas, as well as some light showers over leeward areas during the afternoon with the sea breezes developing.
For the second half of next week, guidance continues to show a some discrepancies between the ECMWF and the GFS. The ECMWF shows a much deeper upper level trough with a surface trough developing near the state. This setup would continue the hybrid tradewind and land/seabreeze pattern. Meanwhile, the GFS shows a much weaker upper level trough, with the surface high north of the state with strengthening trade winds during the second half of the week. The forecast as been updated to favor GFS for now, but will likely change over the next several days as model guidance narrows on a solution.

Aviation

E trade winds will continue to gradually ease and veer to the ESE this weekend, especially over the smaller islands, where wind speeds will trend toward light by tonight. AIRMET Tango for low- level turbulence will be pared back later this morning, removing at least Kauai and Oahu.
Showery and stable low clouds have increased in coverage overnight, in response to a developing low-level trough over the area. Mountain obscuration in windward areas requires AIRMET Sierra, where periods of MVFR VIS/CIG in SHRA may be briefly punctuated by short-lived IFR VIS in +SHRA. Guidance indicates the trough will linger today, thus supporting continued periods of MVFR conditions over windward areas.
The veering of the low-level flow is expected to support the development of the “Maui vortex” by this afternoon, which typically impacts Kahului airport (PHOG) with significant low- level wind shear.

Marine

A 1031 mb surface high, centered around 1200 nm northeast of the state and low about 1100 nm northwest of Hawaii is producing east-southeast winds over the western half of the state and moderate to locally strong easterly winds over the eastern half of the state. Winds will weaken slightly over the next few days as the high weakens and the low shifts north of the state.
A Small Craft Advisory (SCA) will remain in effect for most waters and channels surrounding Big Island, Maui, and Molokai. The advisory may be scaled back late this weekend as winds weaken and shift out of the east-southeast.
Surf heights will remain below advisory thresholds for all shores through the forecast period. A small northwest, medium period swell is forecast to subside by this evening. Thus, small surf can be expected along north and northwest facing shores through the remainder of the weekend. Breezy trade winds will produce choppy, rough surf along east facing shores through at least this evening. Conditions are expected to improve on Sunday. Meanwhile, expect small surf along south and southeast facing shores through the forecast period with occasional pulses of 1 to 2 foot medium to long period swell.

HFO Watches/Warnings/Advisories

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

Data Courtesy of NOAA.gov