A weak surface trough and its associated moisture plume will progress northwestward up the island chain through Friday, bringing a slight uptick in shower activity as it passes through. Otherwise, a lighter background flow will allow for a sea/land breeze pattern to persist into the weekend with showers developing over leeward and interior areas each afternoon, followed by clearing at night. Then trade winds will gradually strengthen late this weekend through next week, shifting the shower focus to windward and mauka areas.
Gentle to moderate east to east-southeast trade winds are pushing a weak surface trough and associated shallow moisture over the islands. The atmosphere is stable, which is suppressing heavy showers, but widespread MVFR ceilings are in place across windward slopes from Big Island to Oahu, where AIRMET Sierra for mountain obscuration remains in effect above 020. Daytime sea breezes will overpower the weak trade wind flow, and additional areas may be added to AIRMET Sierra as ceilings develop over leeward terrain this afternoon. The trough will likely produce MVFR ceilings over windward areas tonight, followed by improvement on Friday as the trough and its moisture lift northward.
Issued at 313 AM HST Thu Jun 18 2026
Trade winds will be mostly at gentle to moderate strength during the next few days as the surface ridge to the north remains weak and a broad surface trough continues to move through the islands over the next few days. The weak trough is currently located near Maui County and is producing some scattered showers over the coastal and offshore waters. Scattered showers will generally decrease over the coastal waters by Friday. Trades may increase slightly over the weekend, with more pronounced strengthening early next week as high pressure builds to the north.
A series of southern hemisphere swells will continue to move through the area during the next week, though much smaller than the recent large event. Nearshore PacIOOS Lanai and Barber Point buoys is showing an increase in the 16 to 18 second energy bands associated with a new south swell filling in today. NOAA buoy 51002 is showing around 4 feet of deep water swell with a period of 14 to 16 seconds with NOAA buoy 51004 SE of the Big Island showing deep water swell of up to 5 feet. With the main fetch aimed just east of the state, surf should remain below advisory thresholds today. The peak of the swell will be today and will gradually decline Friday into the weekend. A series of smaller south- southwest swells will fill in Sunday into the first half of next week and will maintain surf near seasonal averages through next week.
Small surf will prevail on north and east shores through most of the coming week. A slight increase in east shore surf is expected around next Tuesday or Wednesday as trade winds build across the region.
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