The National Weather Service in Honolulu has forecasted that moisture and instability will persist over the Hawaiian Islands today, with such conditions expected to decrease as the weekend draws to a close. Winds across the state have been predicted to weaken and shift to an east-southeasterly direction, then become light and southerly on Sunday. This will primarily allow for a pattern of land and sea breezes, likely leading to afternoon showers in interior and leeward areas.
According to the latest forecast discussion from the NWS, the inversion that typically caps vertical cloud growth has shown some erosion compared to 24 hours ago, hinting at a marginally unstable air mass hanging over the island chain. The NWS also indicated that lighter easterly winds have made a return overnight, influenced by surface high pressure moving eastward and away from the islands. Meanwhile, both Maui and Oahu have seen a prevalence of showers and low clouds, with a potential for afternoon thunderstorms and freezing fog over the Big Island's summits due to an upper-level trough moving across the region.
While instability and moisture are set to decrease by Sunday, current projections include the possibility of isolated showers, particularly in areas where sea breeze convergence takes place. Looking into next week, the forecast becomes less certain as models such as the European Centre for Medium-Range Weather Forecasts (ECMWF) and Global Forecast System (GFS) disagree on the trajectory of weak fronts moving towards the state, potentially impacting weather patterns and winds.
The marine forecast indicates a high-pressure system north of Hawaii is expected to drift east over the weekend, shifting winds to a southeasterly direction today before turning light southerly. This pattern is expected to produce land and sea breezes near shore. North-northwest swells will continue to drive elevated surf, but wave heights are expected to gradually decline today. A series of small, overlapping northwest swells is expected to influence surf conditions through early next week. Minimal change is expected for east- and south-facing shores, although south-facing shores could see a slight increase in wave height from a long-period south-southwest swell beginning late Sunday and lasting through Tuesday, according to the National Weather Service.
