West Kaua’i

Tonight: Mostly clear. Lows 70 to 75 near the shore to around 61 above 3000 feet. Northeast winds up to 10 mph in the evening becoming light.

Sunday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 84 to 90 near the shore to around 76 above 3000 feet. Light winds. Chance of rain 50 percent.

Sunday Night: Mostly clear. Lows 69 to 74 near the shore to around 62 above 3000 feet. Light winds.

South Kaua’i

Tonight: Partly cloudy. Isolated showers after midnight. Lows 71 to 76. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Sunday: Mostly sunny with isolated showers. Highs 81 to 89. Northeast winds around 10 mph. Chance of rain 20 percent.

Sunday Night: Partly cloudy with isolated showers. Lows around 73. Northeast winds around 10 mph. Chance of rain 20 percent.

Kaua’i Mountains

Tonight: Partly cloudy with isolated showers. Lows 65 to 70 in the valleys to around 59 above 4000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Sunday: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs 75 to 83 in the valleys to around 67 above 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Sunday Night: Partly cloudy with isolated showers. Lows around 67 in the valleys to around 59 above 4000 feet. Northeast winds around 10 mph. Chance of rain 20 percent.

North Kaua’i

Tonight: Partly cloudy with isolated showers. Lows 65 to 75. East winds up to 10 mph. Chance of rain 20 percent.

Sunday: Mostly sunny with isolated showers. Highs 77 to 86. East winds up to 10 mph. Chance of rain 20 percent.

Sunday Night: Partly cloudy with isolated showers. Lows 66 to 74. East winds up to 10 mph. Chance of rain 20 percent.

East Kaua’i

Tonight: Partly cloudy with isolated showers. Lows 65 to 78. North winds around 10 mph. Chance of rain 20 percent.

Sunday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 75 to 87. Northeast winds around 10 mph. Chance of rain 40 percent.

Sunday Night: Partly cloudy with isolated showers. Lows 64 to 77. Northeast winds around 10 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A weak surface trough will move through the state the next few days and will bring an increase of clouds and scattered showers on Sunday. With the lack of breezy trades and an increase of humidities, temperatures will feel warmer than usual through at least Monday. Expect trades to strengthen to breezy levels around the middle of next week.

Discussion

A weak surface trough will slowly move through the state the next few days and will bring an increase of moisture. CIMMS MIMIC precipitable water show values of 1.6-1.8 inches just east of the Big Island this afternoon and the latest Hilo sounding is showing a value of 1.55 inches. As this plume of moisture continues to increase over the Big Island this evening and tonight, we should see an increase of rain mainly over windward Big Island tonight. Stable conditions aloft, should keep rainfall intensities at moderate levels and if anything the rainfall should be beneficial to our ongoing drought conditions.
For Sunday, we should see the trough continue to drift westward and will likely bring an increase of moisture to the rest of the state. With the lighter trade winds in place, localized sea breezes should develop across select leeward areas by mid day. Sea breeze convergence should lead to an increase of clouds and scattered showers Sunday afternoon across interior and leeward areas. For areas that do not see any shower activity, with the increase in humidities, temperatures will feel muggy.
There is good model agreement with high pressure building back in to the northeast of the state early next week, which should allow the trade winds to strengthen back to moderate to locally breezy levels by midweek. At the same time, a drier airmass is expected to return to the islands.
We are continuing to monitor the development of Invest 90C far southeast of the state. Central Pacific Hurricane Center has increased the probability of development and now has a high chance of cyclone formation during the next 7 days. Even if a tropical cyclone were to develop, there is good agreement within the global ensemble members for it to stay south of the Hawaiian Islands.

Aviation

A surface trough just east of the Big Island will begin to move through the state tonight, which will bring an increase of showers over windward Big Island and windward Maui. Trade winds will weaken a notch tonight into Sunday with gentle to moderate trade winds expected through Sunday.
Predominately VFR conditions are expected to prevail, however periods of MVFR conditions will be possible especially over PHTO tonight as showers increase.
There are currently no AIRMETs in effect, but an AIRMET for mountain obscurations will be possible tonight into Sunday as showers increase over windward areas of the Big Island and Maui.

Marine

A weak trough just to the east of the islands will transit through the area through the rest of the weekend then dissipate early next week as high pressure north of the area strengthens. Trade winds will stay gentle to locally fresh through Monday due to the trough, then strengthen Tuesday to moderate to locally strong levels with the strengthening high pressure. There is also potential for a tropical disturbance to track south of the waters, this could influence the trade winds speeds.
South facing shores will remain small through the weekend with mainly medium period background energy. A storm force low east of New Zealand has produced seas up to 40 feet per JSON satellite observations, likely impacting the islands during the second half of next week. Confidence has increased that this low will generate a moderate to large long period south swell that may approach or exceed the High Surf Advisory threshold as it peaks.
East facing shores will gradually decline this weekend as trade winds weaken locally and upstream of the state. East shores should then increase next week as trade wind speeds increase. Flat to tiny surf expected along north facing shores through the week.

Fire weather

An increase of humidities are expected over the next few days as a weak surface trough passes through the state. Trade winds are also expected to decrease on Sunday with localized sea breezes developing during the late morning through the afternoon hours. Trade winds are expected to restrengthen Tuesday into Wednesday, with developing dry conditions returning across the state. This could bring elevated fire weather concerns during the second half of next week.

HFO Watches/Warnings/Advisories

None.

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