textproduct: Honolulu

SYNOPSIS

An unstable and somewhat wet trade wind pattern will continue through Tuesday night, with brief downpours possible. From Wednesday into early next week, an area of high pressure north of the islands will push drier air the region and strengthen winds. The result will be a moderate to breezy trade wind pattern.

UPDATE

Issued at 840 PM HST Mon May 18 2026

Similar to yesterday evening, the heavy showers that occurred at select spots during the day have diminished. Only light, isolated showers remain embedded within moderate to locally breezy trade winds favoring windward areas. The forecast remains on track, so no significant updates have been made this evening.

PREV DISCUSSION

Issued at 328 PM HST Mon May 18 2026

Showers across windward and mauka areas, along with the Kona Districts on Big Island, were noted on radar this afternoon. Some showers have been producing moderate to briefly heavy rain, and this has resulted in the issuance of flood advisories on Kauai and on Big Island. These showers will trend down around sunset. Winds were averaging 10 to 20 mph with gusts 20 to 30 mph.

Conditions remain on the humid side this afternoon as we await drier air that should arrive from Tuesday night into Wednesday night. Until that arrives, we will continue to see rather wet trades, meaning we will continue to have the chance for moderate to briefly heavy rain from showers. From late Wednesday onward, we will see noticeably lower PW values (down around 1 inch) going all the way into next week. Aloft, an upper level ridge will become established to our north, even as weak troughing will extend off the southwest coast of the mainland toward Hawaii. This troughing will have little to no impact on our surface weather, as the upper ridging will help keep relatively dry trades established over the region. Dewpoints will fall several degrees as the dry air comes in, allowing a little more cooling overnight for wind-sheltered areas.

AVIATION

Issued at 840 PM HST Mon May 18 2026

Moderate to locally breezy trades expected hold for the next couple days. Low cigs and SHRA will primarily impact windward and mauka locations with some limited spillover to leeward areas. MVFR conds possible in heavier SHRA, otherwise VFR prevails.

AIRMET Sierra is in effect for mtn obsc for windward Kauai, Maui and the entire area of the Big Island.

MARINE

Issued at 840 PM HST Mon May 18 2026

The pressure gradient back from a surface high centered about 1,500 nautical miles northeast of the islands remains tight enough to support moderate to locally fresh trades the next couple of days. The anchored high will expand and strengthen through mid to late week. The resultant very tight gradient back across the Central Pacific will produce fresh to locally strong to near gale force nearshore winds the later half of the week. A Small Craft Advisory (SCA) is currently in effect over the windier zones surrounding Maui County and Big Island. The SCA will likely be expanded in area later this week to account for more areawide strengthened trades.

A small size, short to medium period north northwest swell is expected to fill in overnight into Tuesday. A gale low skirting the Aleutian Islands the next couple of days will send the tail ends of small north northwest swells through late this week.

A series of small, long period south southwest swells will provide near summer average size surf along south-facing shores throughout the week. Strengthening trades later this week will keep short period, elevated eastern wind wave chop alive well into the weekend.

HFO WATCHES/WARNINGS/ADVISORIES

Small Craft Advisory until 6 AM HST Wednesday for Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters- Maalaea Bay-Pailolo Channel.