The National Weather Service in Honolulu has informed residents of continued unstable weather patterns affecting the Hawaiian Islands well into the weekend. According to an advisory released by the NWS, "An upper low near Kauai and Oahu and low level convergent cloud bands riding in on the easterly trade winds bring periods of showers to all islands." The service forecasts these conditions, with potential thunderstorms, to persist over the western half of the state through Saturday morning and part of the Big Island later today.
As showers intensify, the NWS observed that the heaviest rainfalls seem to have spared the smaller islands, mainly hitting the north shore and east Maui, with up to a quarter inch of rainfall, and the north and eastern slopes of Kauai with up to half an inch. This distortion in weather patterns, caused by east-southeasterly steering winds at around 5,000 feet, led to the stronger showers bypassing the smaller islands, which was not what policymakers expected when convened to discuss infrastructure protection.
The trade winds are also anticipated to strengthen and continue influencing weather conditions in the region, promoting the development of more showers. As shared on the NWS Honolulu's official page, "Trade winds will lift unstable clouds over windward island mountain areas where the highest rainfall totals are favored," indicating a trend of localized heavy rainfall across the western islands. The next wave of wet weather is expected as another upper low drops over the western islands by Monday.
In terms of impacts on aviation, unstable conditions leading to periods of "MVFR and isolated IFR ceilings and visibility" due to heavier showers and storm activity have been observed. The NWS has issued an AIRMET SIERRA for temporary mountain obscuration affecting several islands—a disruption that coastal mariners who were bracing for heavy showers now face. Moreover, "AIRMET TANGO remains in effect for Oahu, Molokai, Maui, and the Big Island for tempo moderate turbulence between FL220 and FL350. This is expected to continue through the day," highlighting ongoing concerns for air travel over the islands.
Marine advisories also continue, with a Small Craft Advisory in effect until Friday evening for various channels and coastal waters around Maui County and the Big Island, per NWS Honolulu's weather forecast. These conditions might extend into the weekend as the trades strengthen. Meanwhile, surfers can expect near to above-average surf along north and west facing shores into Friday due to a moderate, long-period northwest swell.
The fire weather outlook remains below critical thresholds despite the unstable conditions. Locally heavy rain and potential thunderstorms have tempered fire risks across the state. The NWS warns that temperature inversion heights, affecting the spread and intensity of rainfall, are measured at 7,500 to 8,500 feet above Maui and the Big Island today. Such inversion layers can lead to more pronounced wet weather in the highest elevation regions, mitigating immediate fire weather concerns.
