Photo Credit: Braden Jarvis

West Kaua’i

Rest Of Today: Partly sunny with scattered showers. Highs 86 to 93 near the shore to around 78 above 3000 feet. Northeast winds up to 10 mph shifting to the south in the afternoon. Chance of rain 40 percent.

Tonight: Partly cloudy with isolated showers. Lows around 71 near the shore to around 62 above 3000 feet. Light winds. Chance of rain 20 percent.

Labor Day: Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 86 to 92 near the shore to around 78 above 3000 feet. Light winds. Chance of rain 40 percent.

South Kaua’i

Rest Of Today: Partly sunny with showers likely in the morning, then sunny with isolated showers in the afternoon. Highs 86 to 92. Northeast winds 10 to 15 mph. Chance of rain 60 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 70 to 76. Northeast winds around 10 mph in the evening becoming light. Chance of rain 40 percent.

Labor Day: Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 86 to 92. Light winds. Chance of rain 30 percent.

Kaua’i Mountains

Rest Of Today: Partly sunny. Showers likely early in the morning, then scattered showers in the late morning and afternoon. Highs 75 to 86 in the valleys to around 68 above 4000 feet. East winds up to 10 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 65 to 71 in the valleys to around 59 above 4000 feet. East winds around 10 mph. Chance of rain 50 percent.

Labor Day: Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 76 to 86 in the valleys to around 68 above 4000 feet. East winds around 10 mph in the morning becoming light. Chance of rain 50 percent.

North Kaua’i

Rest Of Today: Partly sunny with scattered showers. Highs 77 to 89. East winds up to 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 66 to 74. East winds up to 10 mph in the evening becoming light. Chance of rain 50 percent.

Labor Day: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 78 to 88. East winds up to 10 mph. Chance of rain 40 percent.

East Kaua’i

Rest Of Today: Mostly cloudy with showers likely early in the morning, then mostly sunny with isolated showers in the late morning and afternoon. Highs 76 to 89. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 65 to 78. Northeast winds around 10 mph in the evening becoming light. Chance of rain 50 percent.

Labor Day: Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 77 to 89. East winds around 10 mph. Chance of rain 40 percent.

Detailed Forecast

Synopsis

Winds will decrease and become variable daytime sea breezes and nighttime land breezes by Labor Day. Limited moisture and instability will cap rainfall as it favors windward and mauka areas mainly at nights and in the mornings. The subtropical jet stream will bring high cloudiness to Maui county and the Big Island next week. Deeper moisture overspreading the Big Island could lead to more active afternoon and evening showers there around the middle of next week.

Discussion

High pressure far north of the main Hawaiian Islands drives moderate trades across local waters this morning. Overnight soundings showed total precipitable water of 1.25 to 1.45 inches over the islands, with inversion heights around 9500 feet. Satellite and radar loops show scattered to patchy broken low clouds and isolated to scattered showers riding in on the trades, mainly upwind of the central islands.
Models show the high far to the north will weaken as broad surface troughing develops east of the islands. Trades will continue to weaken into early next week. Surface troughing will slide westward across the islands on Labor Day and will be located west of the islands on Tuesday. This will leave the islands temporarily in a gentle southeast background flow that will allow development of daytime sea breezes and nighttime land breezes. A developing upper trough will raise and weaken the subsidence inversion over the islands early next week. Windward and mauka showers will transition towards an afternoon and evening interior and leeward focus by Labor Day and Tuesday. Models also show a surge in moisture mainly across the Big Island toward the middle of next week. This should result in quite a bit more afternoon cloudiness and convection for the southern end of the chain, with at least a small chance of afternoon upslope thundershowers Wednesday and Thursday. In contrast, it may be quite dry with few if any showers across the western end of the chain at the same time as the trades try to build back in.
Expect troughing near the islands to weaken by Wednesday, allowing a return of easterly trade winds at gentle to locally breezy speeds. With models showing lingering moisture over the islands late in the week, expect a hybrid pattern of windward and mauka showers during the nights, and limited afternoon showers over leeward and upslope areas.

Aviation

The high pressure ridge north of Hawaii will weaken today resulting in decreasing trade winds and a hybrid sea breeze pattern. Clouds and a few showers will develop over island interior sections each afternoon along sea breeze convergence zones. Lighter winds on Monday and Tuesday will produce a more solid sea breeze pattern across the state. VFR conditions will prevail outside of showers.
No AIRMETs in effect.

Marine

Surface ridge far north of the waters will weaken today causing the trade winds to become gentle to locally fresh. Thus, the Small Craft Advisory has been canceled for typical windy waters around Maui County and the Big Island this morning. A developing broad surface trough will cause winds to veer to the southeast and weaken. Light to locally moderate breezes will continue through the middle of the week.
South shore surf will remain small today before a moderate (3 to 4 foot), south to south-southwest swell is expected to slowly fill in Monday and peak late Monday night into Wednesday. Surf is expected to get near High Surf Advisory levels, then slowly decline through rest of the week.
Surf along north and west facing shores will have a small bump today as a small northwest swell generated by former Tropical Cyclone Damrey continues to fill in. Nearshore PacIOOS buoys at Hanalei and Waimea have shown signs of the swell filling in this morning. The swell is expected to gradually shift out of the north- northwest late Monday as it fades out through Tuesday.
Surf along east facing shores will trend lower today into the middle of the week as the trades weaken.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov