textproduct: Honolulu

SYNOPSIS

Moderate trades will gradually weaken as a low pressure system tracks southward eroding the surface ridge just north of the islands. Lighter winds will develop localized land and sea breezes through the weekend and early next week, increasing clouds and showers for interior and leeward areas. Early next week, increasing moisture will move up the island chain from the southeast, increasing shower activity for the state Monday through Wednesday. Trades return late Wednesday and persist through the remainder of the forecast period.

DISCUSSION

A strong surface ridge positioned north of the Hawaiian Islands will begin to weaken as a broad area of low pressure tracks southward from the Aleutian Islands. As this occurs, the ridge will begin to erode and the local pressure gradient will also weaken, leading to lighter winds and the potential for localized land and sea breeze development, persisting through the weekend and lasting through early next week. This will prompt increased afternoon cloud and showers across interior and leeward areas during the afternoons, followed by overnight clearing.

Latest model guidance continues to support a large plume of tropical moisture lifting northwestward over the island chain Monday through Wednesday. The aforementioned low pressure system will start to lift northward away from the islands during this time, opening the door for ridging to rebuild and allow trades to strengthen once again. This return to a more typical trade pattern will bring windward and mauka favoring showers for the remainder of the forecast period.

AVIATION

Moderate trades should decrease slightly over the weekend. Low cigs and SHRA along windward and mauka locations. MVFR conds possible in SHRA otherwise VFR prevails.

AIRMET Sierra in effect for mountain obscuration on Maui and Big Island for clouds and showers.

MARINE

Moderate to fresh trade winds will steadily ease into the light to moderate range by Sunday as the surface ridge weakens in response to broad low pressure developing near the Aleutian Islands. This will translate to localized land and sea breezes near the coasts late this weekend through early next week. A return of moderate to fresh easterly trades is likely by midweek as the ridge restrengthens.

An active pattern is in store for surf along south-facing shores as we head into June due to a series of recent gale- to storm- force lows passing through our swell window near New Zealand over the past week. Overnight observations at the nearshore buoys have been trending up within the 18 second band, which supports advisory-level surf today. Expect similar conditions to hold through Sunday. As the swell gradually begins to ease Monday, long-period forerunners from the next south-southwest swell are expected to arrive. Heights may briefly dip below the advisory level by Monday night, but as the next swell fills in, surf will likely return to these levels Tuesday through midweek as it peaks. A gradual downward trend is then expected through the second half of next week.

A combination of advisory-level surf this weekend and water levels hovering above predicted levels could lead to some wave runup issues, with water sweeping across areas of beaches that typically remain dry during the afternoon peak daily tide cycles. Water levels will steadily lower each day early next week as the next large south swell arrives.

Surf along north facing shores will remain small through Monday, then potentially trend up as a small north swell arrives by midweek.

Expect surf along east-facing shores to gradually ease through early next week as trade winds relax. A slight increase is possible Tuesday and Wednesday due to a combination of strengthening trades and a wrapping north swell.

HFO WATCHES/WARNINGS/ADVISORIES

High Surf Advisory until 6 PM HST Sunday for Niihau-Kauai Leeward-Waianae Coast-Kahoolawe-Maui Leeward West-Kona-Kauai South-East Honolulu-Honolulu Metro-Ewa Plain-Molokai Leeward South-Lanai Leeward-Lanai South-Maui Central Valley South-South Maui/Upcountry-South Haleakala-Big Island South-Big Island Southeast.