Photo Credit: Brendan Stephen

West Kaua’i

Today: Mostly sunny. Breezy. Highs around 87 near the shore to around 77 above 3000 feet. Northeast winds up to 20 mph.

Tonight: Partly cloudy. Lows 70 to 75 near the shore to around 61 above 3000 feet. Northeast winds 10 to 15 mph.

Sunday: Mostly sunny. Highs around 90 near the shore to around 78 above 3000 feet. Northeast winds 10 to 15 mph.

South Kaua’i

Today: Partly sunny. Breezy. Isolated showers in the morning. Highs around 86. Northeast winds 15 to 25 mph. Chance of rain 20 percent.

Tonight: Breezy. Mostly cloudy with isolated showers. Lows 68 to 74. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Sunday: Partly sunny. Breezy. Isolated showers in the morning. Highs 83 to 89. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Kaua’i Mountains

Today: Mostly cloudy. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 73 to 81 in the valleys to around 70 above 4000 feet. East winds up to 20 mph increasing to 10 to 25 mph in the afternoon. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 61 to 66 in the valleys to around 56 above 4000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

Sunday: Mostly cloudy. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 74 to 85 in the valleys to around 68 above 4000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

North Kaua’i

Today: Partly sunny with isolated showers. Highs 76 to 86. East winds up to 15 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy with isolated showers. Lows 64 to 74. East winds 10 to 15 mph. Chance of rain 20 percent.

Sunday: Partly sunny with isolated showers. Highs 77 to 91. East winds 10 to 15 mph. Chance of rain 20 percent.

East Kaua’i

Today: Breezy. Partly sunny with isolated showers. Highs 75 to 86. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy with isolated showers. Lows 62 to 75. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Sunday: Partly sunny with isolated showers. Highs 75 to 86. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A large area of high pressure generally north of the Hawaiian Islands will hold the next several days. This will maintain the ongoing typically dry summertime trade wind pattern. Thicker more areal coverage clouds and more frequent showers will continue to favor more windward exposures and mauka zones. The next decent chance of more island-wide rain may be early next week in response to a vicinity upper level disturbance northeast of the state.

Discussion

There is little variance in forecast philosophy under this near static Central Pacific synoptic pattern. Summertime dry trades persist as a pair of highs centered northwest and northeast of the islands drive primarily fresh to locally strong easterlies. Relatively lower inversion 5-6k foot heights will result in a more shallow boundary layer, in tandem with dry mid to upper level moisture (< 30% RH) advecting in across the chain, nearly guarantees a stable enough island environment that will generally support windward and mauka cloudier skies and occasional showers. The usual suspect caveats of cloudier, slightly more wet afternoon Kona and Ka'u slope conditions with infrequent leeward sprinkles and partly cloudy skies riding over local area ridge tops still apply.
The development of an upper level disturbance forming in the middle of northern ridging will be the impetus of gradually weakening trades. The reflection of lowering surface pressures, along with the proximity of a subtropical jet, may work in favor of increasing more areawide pockets of better organized early week shower activity. The main question marks to increased shower activity will be whether or not there will 1) be ample column moisture within a deepened, marginally-destabilized boundary layer and 2) the location of the upper disturbance in relation to the islands. The wettest period is shaping up to be on Days 6 & 7 (next Thursday and Friday). This is the time at which inversions are slightly higher (closer to 6.5k ft), lapse rates are the greatest (5 to 6 deg C in lowest 3 km) and moisture is highest (> 80% RH). These three elements best come in-line over Big Island and Maui Counties in closing out the traditional work week.

Aviation

Breezy to locally windy trades will continue for the next few days. SHRA and low cigs will favor windward and mauka locations. Brief MVFR conds are possible in any SHRA. VFR conds should generally prevail.
AIRMET Sierra for mtn obsc remains in effect for N thru SE sections of Kauai, Oahu, Molokai, Maui and the Big Island.
AIRMET Tango for mod low-level turb lee of island terrain will remain in effect for the next several days due to the strong trades.

Marine

A strong high pressure ridge north of the Hawaiian Islands will continue to keep fresh to strong trade winds in the forecast through the weekend and into much of next week. Typical windier channel areas will see wind speeds near gale forecast at times with seas approaching 10 foot advisory levels. A Small Craft Advisory (SCA) remains in effect for all Hawaiian Coastal Waters through early Sunday morning. A subtle decrease in the trade winds are forecast by early next week. The SCA winds will linger in more than just the typical windier waters for most of next week.
A more significant long period south swell will fill in late tonight, reaching High Surf Advisory (HSA) levels for south facing shores on Sunday and Monday. West facing shores will see a decent south swell wrap, boosting surf heights as well, with the Big Island west facing shores likely reaching HSA levels on Sunday. A gradual downward trend is expected Tuesday through midweek.
Due to the strong trade winds upstream of the state, surf along east facing shores will remain rough and choppy through early next week. A downward trend is possible around midweek as the upstream fetch weakens and the local trades begin to ease.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Sunday for all Hawaiian waters,

Data Courtesy of NOAA.gov