Honolulu residents can expect a shift in weather conditions as generally dry and stable climates give way to a warm, muggier atmosphere next week. According to a forecast by the National Weather Service in Honolulu ("NWS"), a slight increase in showers is on the radar for Sunday into Monday due to an approaching upper low and higher moisture content in the air.
The currently weak trade winds are a result of a ridge over the region, as well as a trough located north of the state, which is disrupting the normal pressure gradient. This will permit more localized breezes to take over, “Sea breezes interacting with the background trade wind flow will produce thicker afternoon cloudiness,” the NWS reported. These conditions may spur light showers, particularly in the Kona and Ka'u regions, and the leeward West Maui mountains. Rain, however, is expected to be minimal through tonight due to the dry and stable air mass in place above the 7k foot trade inversion.
In the greater context, residents and visitors need to keep an eye on Tropical Cyclone Kiko. The system, reclassified as a Category Four Hurricane, has just entered the Central Pacific and is predicted to weaken to a tropical storm by the time it reaches the vicinity of Hawaii's northern offshore waters between Tuesday and Wednesday. As Kiko advances, the NWS states, “A dry slot of air leading the cyclone will pass across the state Monday and briefly lower early day rain chances.” Following this, an increase in statewide rainfall is anticipated through the mid-week as Kiko draws near.
Marine conditions are also set to change, with a weak trough leading to gentle to moderate trade winds and localized sea breezes into the weekend. Surf might swell along east-facing shores as Kiko approaches, potentially reaching advisory or even warning levels by late Monday or Tuesday. A moderate long period south-southwest swell is filling in to lift surf above the summer average, with another swell expected Tuesday. For coastal areas, a Coastal Flood Statement is in place owing to peak monthly high tides and water levels running higher than predicted through Sunday afternoon.
The forecast for aviation indicates light to moderate trade winds across terminals, but a switch to local breezes at airports like Lanai (KHNY) and Big Island (HTO, HKO) will occur as the trough moves closer to the island chain. Meanwhile, for fire weather concerns, the NWS Honolulu provided some reassurance. Humidities will briefly dip, and showers may increase next week due to Kiko's proximity, but winds will stay below the critical thresholds for fire weather conditions.
