textproduct: Honolulu

SYNOPSIS

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.

SHORT TERM UPDATE

Surface observations show light offshore land breezes beginning to transition to onshore sea breezes across much of the state this morning as background winds remain light, while satellite and radar show a plume of deeper moisture associated with a weak surface trough bringing a slight uptick in cloud and shower coverage across the central and eastern portions of the island chain. The trough and its associated moisture plume will very gradually progress northwestward over the western end of the state by Friday, shifting the shower focus along with it. Moderate east-southeasterly winds will fill in across the state in its wake, especially across the eastern half later today into tomorrow. With the lighter winds today, land breezes will continue to give way to sea breezes by this afternoon, causing clouds and a few showers to develop over leeward and interior areas, followed by partial clearing overnight as land breezes redevelop.

PREV DISCUSSION

Issued at 313 AM HST Thu Jun 18 2026

A weak surface trough is passing over Molokai and Oahu this morning and will gradually move up the island chain through Friday before lifting north of the area and dissipating. A plume of moisture accompanying this trough will help bring increased cloud and shower coverage in its vicinity as it progresses northwestward. The positioning of this surface trough and a series of fronts passing well north of the state will keep the trade winds disrupted through the rest of the work week and into the weekend, with generally moderate east- southeasterly winds across the eastern half of the state and light to moderate east- southeast winds across the western half. This weaker, slightly veered low- level wind pattern will allow a sea and land breeze cycle to commence, bringing clouds and a few showers across leeward and interior areas each afternoon, and clearing overnight. However, increased cloud cover in the vicinity of the trough may inhibit the sea and land breeze cycle. In addition hot and muggy conditions will persist through the weekend with dewpoints into the 70s. Please remember to hydrate and take breaks when you need them.

Trade winds will gradually ramp up late this weekend through next week, becoming moderate to breezy by Wednesday as the surface trough weakens and moves westward, and the subtropical high to the far northeast finally regains control over the Central Pacific. Batches of moisture will filter in on the strengthening trades, supporting periodic upticks in windward and mauka showers next week.

AVIATION

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.

MARINE

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.

HFO WATCHES/WARNINGS/ADVISORIES

None.