textproduct: Honolulu

SYNOPSIS

A slightly unstable and somewhat wet trade wind flow will continue over the next few days with brief downpours possible. An increasingly stable, windy trade wind flow will develop during the second half of this week.

SHORT TERM UPDATE

Issued at 830 PM HST Sun May 17 2026

This evening, heavy showers that occurred earlier in the day across portions of the state have largely diminished. Radar and satellite imagery still shows a few lighter windward and mauka showers at this time, which will likely continue throughout the night. The remainder of the forecast remains on track, so no updates have been made this evening.

PREV DISCUSSION

Issued at 344 PM HST Sun May 17 2026

Scattered heavy showers developed over select areas across the state today due to the higher than normal moisture values combined with some afternoon day time heating. As we head into the late afternoon and evening, the intensity of the showers should generally decrease. The one exception is over windward Big Island and possibly east Maui, where we are seeing frequent trade wind showers. Hilo sounding showed over 2 inches of precipitable water values this afternoon and a wet trade wind pattern could very well continue for the Big Island through the middle of the week with frequent showers over windward areas.

Overall, broad troughing aloft combined with higher than normal precipitable water values and moderate easterly trade winds will continue to produce brief downpours at times through the middle of the week. Showers will generally favor windward areas during the overnight and morning hours with scattered leeward showers developing during the afternoons. Dewpoints will continue to linger in the upper 60s to low 70s, which should make temperatures feel warmer than normal.

Increased stability and stronger trade winds are expected by Thursday. Latest global guidance from the GFS and ECMWF are in good agreement with a strong high developing far north of the state, which should result in windy conditions. Winds could very well reach Wind Advisory thresholds Thursday into Friday for select areas downstream of terrain. Drier conditions are also expected during this time, but scattered showers should continue to ride in with the windy trade winds especially during the night and early morning hours.

AVIATION

Issued at 830 PM HST Sun May 17 2026

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

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

MARINE

Issued at 830 PM HST Sun May 17 2026

The pressure gradient back from a surface high centered 1,400 nm northeast of the islands remains tight enough to support moderate to locally fresh trades the next few days. This anchored high will strengthen and expand past mid week. The resultant tightening gradient will produce fresh to locally strong trades during the later half of the week.

A small, medium period north northwest (320-330 degree) swell and associated north-facing surf will continue to slowly decline through early Monday morning. A small size, short to medium period north northwest bump in swell late Monday will provide an additional foot or two upon north-facing shore surf later in the day through Tuesday.

The arrival of a couple of medium to long period south southwest (200 degree) swells will maintain near summertime average surf along southern facing shores through most of the week. Strengthening trades later this week will keep short period, elevated wind wave chop alive through the week.

Water levels peaking between 2.5 to 3.0 ft MLLW during high tides the next couple of days will result in some minor overwash within low lying coastal areas.

HFO WATCHES/WARNINGS/ADVISORIES

None.