Photo Credit: Brendan Stephen

West Kaua’i

Today: Mostly sunny. Isolated showers in the afternoon. Highs 78 to 86 near the shore to around 72 above 3000 feet. East winds up to 10 mph shifting to the southeast in the afternoon. Chance of rain 20 percent.

Tonight: Mostly clear. Haze. Lows 64 to 69 near the shore to around 57 above 3000 feet. Light winds.

Saturday: Mostly sunny. Haze through the day. Isolated showers in the afternoon. Highs 77 to 85 near the shore to around 72 above 3000 feet. East winds up to 10 mph shifting to the south around 10 mph in the afternoon. Chance of rain 20 percent.

South Kaua’i

Today: Mostly sunny with isolated showers. Haze in the afternoon. Highs 77 to 85. Light winds. Chance of rain 20 percent.

Tonight: Mostly clear. Haze. Lows around 67. Light winds.

Saturday: Mostly sunny. Haze through the day. Isolated showers in the afternoon. Highs 78 to 84. West winds up to 10 mph shifting to the southwest around 10 mph in the afternoon. Chance of rain 20 percent.

Kaua’i Mountains

Today: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 72 to 80 in the valleys to around 64 above 4000 feet. Light winds. Chance of rain 40 percent.

Tonight: Mostly clear. Isolated showers in the evening. Haze through the night. Lows 57 to 66 in the valleys to around 55 above 4000 feet. Light winds. Chance of rain 20 percent.

Saturday: Sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Haze through the day. Highs 73 to 80 in the valleys to around 64 above 4000 feet. Light winds becoming southwest up to 10 mph in the afternoon. Chance of rain 40 percent.

North Kaua’i

Today: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 74 to 82. Southeast winds up to 10 mph shifting to the southwest in the afternoon. Chance of rain 30 percent.

Tonight: Mostly clear. Isolated showers in the evening. Haze through the night. Lows 60 to 68. Light winds. Chance of rain 20 percent.

Saturday: Mostly sunny with isolated showers. Haze. Highs 74 to 82. Light winds becoming northwest up to 10 mph in the afternoon. Chance of rain 20 percent.

East Kaua’i

Today: Mostly sunny with isolated showers. Haze in the afternoon. Highs 72 to 83. Southwest winds up to 10 mph shifting to the south in the afternoon. Chance of rain 20 percent.

Tonight: Mostly clear. Isolated showers in the evening. Haze through the night. Lows 60 to 70. Light winds. Chance of rain 20 percent.

Saturday: Mostly sunny with isolated showers. Haze. Highs 73 to 84. Southwest winds up to 10 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Moderate to locally breezy trade winds will weaken tonight into Friday as a front approaches and stalls to the northwest. Overnight land breezes and afternoon sea breezes will prevail from Friday through early next week with the weak background flow becoming more southerly. A cold front may move over portions of the state by mid week next week and bring beneficial rain and breezy winds.

Discussion

Current radar and satellite imagery show isolated to scattered showers moving into mainly windward areas on the light to moderate east-southeast trades this morning. The trades will continue to weaken and veer southeast today in response to an approaching weak cold front from the northwest. This will allow for a hybrid pattern to emerge with some limited windward showers riding in on the weakening trades and some isolated sea breeze activity over the more wind-protected leeward areas. Then as the front inches closer and stalls north of the state this weekend, winds will continue to weaken and veer south and then eventually southwesterly across the western end of the island chain. During this period, land and sea breeze activity will become more widespread, allowing limited cloud and shower development over leeward and interior areas during the day and clearing at night.
Model guidance has been consistently showing that an upper level trough will dive down and sweep across the central Pacific and finally help to drive the next front through at least a portion of the island chain by mid week next week. As the southwesterly flow strengthens across the western half of the state late this weekend into early next week in advance of this front, this may be enough to overcome the land and sea breeze pattern for Kauai and Oahu and focus clouds and showers over leeward areas…especially if any prefrontal convergence bands materialize in the southwesterly flow. The latest global model runs look to have come into slightly better agreement on the timing of this front, bringing it to Kauai's doorstep on Tuesday evening, then slowly moving through the middle of the island chain by Wednesday evening before it stalls. This frontal passage looks to bring some beneficial rain to the area, along with breezy north-northeasterly winds for the western half of the state. Convergence along this dissipating frontal boundary, an abundance of upstream moisture, and a new plume of moisture associated with a low level disturbance moving towards the eastern end of the state will keep rain chances in the picture through the latter part of the week.
Finally, a hot spot over Halemaumau Crater on the Big Island continues to be seen on infrared satellite imagery. The University of Hawaii Vog Model shows that SO2 emissions should remain confined to portions of the Big Island and adjacent waters to the west and southwest through this morning. Then, assuming constant SO2 emissions, vog could begin to increase across some of the smaller islands by tonight as the background flow becomes more southerly.

Aviation

Trade winds will become further disrupted today and tonight as they ease and shift southeasterly. This will allow daytime sea breezes and overnight land breezes to become dominant across the state. Showers will favor windward areas through the early morning hours, with a few showers possible over the island interiors this afternoon. Showers will remain fairly sparse tonight, with a few showers possible near the island coasts.
No AIRMETs are currently in effect.

Marine

Little change to the marine forecast with the morning package. The current northwest swell continues to run a little above guidance, but is on the decline, so surf is expected to fall advisory levels over the next few hours. With this in mind, the High Surf Advisory has been cancelled. Surf is expected to rise again Saturday, reaching advisory levels late in the day, with warning level surf expected to arrive Saturday night.
A surface ridge has sunk southwards into the northern offshore waters, spreading lighter south to southeast winds to the islands. Winds are a little stronger near the Big Island versus Kauai due to the placement of the ridge. The ridge is expected to linger near Kauai and Oahu today and tomorrow, and push over Maui County Sunday. This will bring gentle to locally moderate southwest winds north of the ridge and southeast winds south of the ridge. A front approaching from the northwest is expected to produce increased southwest winds around Kauai and Oahu early next week, and the front may reach Kauai as early as Tuesday night. The front will bring the chance for thunderstorms to the northern offshore waters Saturday through Tuesday.
As mentioned above, the current northwest swell is on the decline, but surf is expected to be below advisory levels soon if it isn't already. A series of large to potentially extra large northwest swells is due this weekend and next week. A large, very intense low formed in the northwest Pacific Wednesday, and produced an elongated fetch pointed toward the islands. Long period forerunners of the swell will build through Saturday, and surf along north and west shores, including leeward Big Island, should far exceed High Surf Warning thresholds during the peak of the swell Saturday night into Sunday. A Small Craft Advisory (SCA) will also be needed for seas in excess of 10 ft for waters exposed to the swell. The large northwest Pacific gyre will send additional pulses of large to potentially extra large swell Monday night through Wednesday.
Surf along east and south facing shores will remain small through the week.

Fire weather

No critical fire weather conditions are expected for the next seven days. A daytime sea breeze and overnight land breeze pattern will develop beginning later today into early next week as a weak southerly background flow takes over. Relative humidities will stay above critical levels through the forecast period. An approaching front has the potential to move through the state from mid- to late week next week, bringing breezy northeasterly winds and providing much needed rainfall to leeward locations.

HFO Watches/Warnings/Advisories

None.

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