West Kaua’i

Tonight: Mostly clear with isolated showers. Lows 70 to 76 near the shore to around 63 above 3000 feet. Northeast winds up to 15 mph shifting to the east after midnight. Chance of rain 20 percent.

Wednesday: Sunny with isolated showers. Highs 86 to 93 near the shore to around 79 above 3000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Wednesday Night: Mostly clear. Lows 71 to 76 near the shore to around 62 above 3000 feet. Northeast winds up to 10 mph in the evening becoming light.

South Kaua’i

Tonight: Partly cloudy with isolated showers. Lows around 75. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Wednesday: Mostly sunny with isolated showers. Highs 83 to 92. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Wednesday Night: Partly cloudy. Isolated showers after midnight. Lows around 74. Northeast winds around 10 mph. Chance of rain 20 percent.

Kaua’i Mountains

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 65 to 71 in the valleys to around 60 above 4000 feet. East winds up to 15 mph becoming around 10 mph after midnight. Chance of rain 30 percent.

Wednesday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 76 to 86 in the valleys to around 68 above 4000 feet. East winds 10 to 15 mph. Chance of rain 30 percent.

Wednesday Night: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 65 to 71 in the valleys to around 60 above 4000 feet. East winds around 10 mph. Chance of rain 30 percent.

North Kaua’i

Tonight: Partly cloudy with isolated showers. Lows 66 to 75. East winds up to 15 mph becoming around 10 mph after midnight. Chance of rain 20 percent.

Wednesday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 79 to 89. East winds 10 to 15 mph. Chance of rain 30 percent.

Wednesday Night: Partly cloudy with isolated showers. Lows 66 to 75. East winds around 10 mph. Chance of rain 20 percent.

East Kaua’i

Tonight: Partly cloudy with isolated showers. Lows 66 to 78. East winds 10 to 15 mph. Chance of rain 20 percent.

Wednesday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 75 to 88. East winds 10 to 15 mph. Chance of rain 30 percent.

Wednesday Night: Partly cloudy with isolated showers. Lows 66 to 78. East winds around 10 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A large scale trough extending from low pressure centered far northeast of the islands will result in weaker statewide winds. Dry and stable conditions will prevail under light variable or weak trades the next several days.

Discussion

Central Pacific troughing remains embedded within general broad high pressure ridging encompassing the Pacific east of the date line. East Pacific upper ridging still controls the regional weather pattern and this dry trade weather pattern will rule through the Labor Day holiday weekend. A higher pocket of mid layer moisture depicted in visible satellite imagery as a plume of thicker, low topped stratocumulus cloud cover moved onto Big Island and surrounding waters today. Stable won out again as there was not much in the way of measurable precipitation. The zonal orientated upper ridge will expand west and fully envelope the island chain by the end of the week. Winds will remain light to locally moderate as weak troughing disrupts the downstream pressure gradient from a surface high northeast of the state. This high will also be in close enough proximity of the state to not allow much of a gradient to develop. Inland temperatures will warm into the upper 80s with more wind-sheltered urban sites reaching the lower 90s.
The majority of island rain gauges remained dry once again with only a few hundredths falling along windward upslope mauka. Upper level ridging directly over the state will limit shower activity as temperature inversion heights remain under a relatively shallow 7k feet. This very warm pattern will continue through the holiday. Anemic trade flow will allow for more local sea/land breeze behavior to become more pronounced across sheltered leeward interiors. A converging sea breeze into east trade wind flow in response to warming west-facing slopes will produce daily thicker afternoon cumulus and isolated shower activity. Higher windward exposed terrain may also experience brief nocturnal showers but nothing more than a daily tenth of inch is expected as they skirt by in the easterlies.

Aviation

A moderate, stable, and somewhat dry trade wind flow will continue during the next few days. Periods of MVFR conditions will briefly affect windward slopes, and aside from isolated areas of afternoon MVFR ceilings on leeward terrain, VFR will dominate over most leeward sections.

Marine

High pressure north of the Hawaiian Islands will maintain moderate to fresh trades through the rest of the week. A front approaching from the north will weaken winds to gentle to moderate ranges over the weekend.
A small, long period south swell will trickle in tonight into Wednesday maintaining below average surf along south facing shores. Another pulse of a small, long period south swell should start building late Wednesday night into Thursday. This swell is expected to peak Friday producing near average surf before declining over the weekend and returning to background levels early next week.
Small choppy surf along east facing shores will hold into Thursday before dropping notch as winds locally and upstream ease through the weekend into early next week.

Fire weather

Dry weather conditions will continue to maintain elevated wildfire concerns through the week. Far interior relative humidity values will lower to between 30 and 40% RH during the early afternoon hours. Low wind speeds will be the limiting factor for reaching critical fire thresholds. Low %RH and light east to variable breezes will be the main theme through the remainder of the month. Interior temperature inversion heights will range from around 7k to 7.5k ft the next few days.

HFO Watches/Warnings/Advisories

None.