Heavy rainfall is on today's forecast for Kauai, raising concerns for potential Flash Flooding on the island, according to the NWS - Honolulu Weather Forecast. The advisory also notes a possibility of localized heavy showers in other areas, while moderate trade winds are expected to usher in a more typical weather pattern beginning Sunday.
The closed low north of Kauai is driving the cyclonic flow across Hawaii, as reported by the National Weather Service, and while the greatest concentration of thunderstorms seems to have avoided direct impact, the islands are not entirely out of range. Isolated thunderstorms were reported near the Kauai Channel late last night, and boundary layer winds could shift, increasing convergence and chances for intensified convection over Kauai in the morning hours.
Forecast models are somewhat uncertain but recent trends suggest a pivot of a potent shortwave toward Kauai, which might enhance low-level convergence and precipitation within the Flood Watch area, especially between 5 am to 2 pm HST. Isolated thunderstorms are not ruled out, and "isolated thunder likewise remains in the forecast for Kauai," as per the NWS - Honolulu Weather Forecast. Elsewhere, on Oahu and the Big Island's slopes, the weather service is expecting scattered showers and possible thunderstorms, leaning on afternoon convective activity prompted by local terrain heating.
Looking ahead, the forecast indicates a gradual westward departure of deeper moisture, though Kauai could still experience pockets of heavy showers through tomorrow night. Despite a lack of organization that negates the need for a Flood Watch extension, low-level ascent will come to a halt as trades return, which might support a mix of wind- and sea breeze–driven showers, particularly on the leeward sides of the islands as we head into tomorrow.
The aviation outlook includes periods of MVFR conditions in shower bands, primarily over Kauai, with clouds and showers expected to wane over Oahu by the afternoon while persisting over Kauai and Niihau. MVFR conditions may also appear in parts of the Big Island, driven by tropical moisture influx from the south. Meanwhile, AIRMET Sierra remains effective for mountain obscuration over Kauai and Oahu until conditions improve later in the day. The marine forecast notes that a surface trough to the west of Kauai will move westward and weaken, with variable winds around the area until high pressure rebuilds to the north, bringing a resurgence of moderate easterly trade winds into next week.
While fire weather concerns remain low for the weekend, the anticipated return of moderate trade winds and drier conditions by next week could shift the outlook as lighter winds and high relative humidity tend to reduce fire risks. Meanwhile, surf conditions are expected to follow the swells with a slight increase along south-facing shores and a gradual decline of the north-northeast swell through the weekend, with trade wind chop increasing once the trades kick back in by Sunday.
