textproduct: Honolulu

SYNOPSIS

Moderate to locally breezy trades will prevail through Tuesday, decreasing slightly by midweek, before easing to a more light and variable pattern by this weekend. Shower activity will be kept to a minimum as a cooler and drier airmass succumbs the Hawaiian Islands. A cold, upper-level trough makes an appearance late in the week and may slightly enhance trade wind showers, but any meaningful rainfall remains unlikely throughout the week.

DISCUSSION

As the weak trough responsible for the recent showers across the Big Island gradually shifts northeast, a broad area of high pressure slowly builds just northwest of the Hawaiian Islands. This transition will enforce moderate to locally breezy trades across the state over the next couple of days. Current observations show winds ranging from 15 to 25 knots (around 17 to 29 mph) statewide, and guidance is suggesting this pattern will continue through at least Tuesday. While most areas will remain just below Wind Advisory thresholds (sustained speeds of 30 to 39 mph and gusts 50 to 57 mph), the usual wind-prone locations could occasionally flirt with those criteria.

Rainfall will take a noticeable step back in the days ahead as drier air continues to filter in. Model guidance indicates precipitable water values dropping to around three standard deviations below normal -- an impressively dry setup. Any showers that do manage to develop will be sparse and largely confined to windward and mauka areas, especially over Maui and the Big Island where the last bit of residual moisture lingers. Even there, a strengthening low-level inversion and limited moisture will keep activity minimal.

Adding a bit of intrigue, some guidance hints at a slight uptick in thunderstorm potential of around 10 percent over the Big Island, particularly along the southern slopes starting Tuesday afternoon. However, with moisture levels running exceptionally low, any storms that do form would likely be "dry" thunderstorms, producing lightning with little to no rainfall. While this setup is common in parts of the mainland during the summer, it remains a relatively rare scenario for Hawaii. That said, the atmosphere may ultimately be too dry to support storm development at all, which is why thunderstorms are not currently in the official forecast, but it's certainly something worth keeping an eye on over the next day or so.

Looking ahead, the aforementioned high pressure system will gradually drift northeast and weaken as the week progresses. This will allow trades to ease, becoming lighter and more variable by Friday and into the weekend. At the same time, a weak upper-level trough may pass through late in the week. Even so, moisture remains limited, and any meaningful increase in rainfall still appears unlikely at this time. As always, we'll continue to monitor and refine the forecast as the pattern evolves.

AVIATION

Moderate to breezy NE trades persist for the forecast period. Low cigs and SHRA possible across windward and mauka locations. MVFR conds in heavier SHRA however VFR prevails.

AIRMET Tango is in effect for mod turb downwind of terrain. It is also in effect for mod turb between FL240-FL360.

MARINE

Fresh to strong northeast trade winds will persist through Tuesday, driven by a strong high-pressure system north of the islands. Winds are expected to ease during the second half of the week as a trough develops east of the state and the high far north of the state shifts further east. Another trough is expected to develop north of the state towards the end of the week, which could produce light winds across the state next weekend.

A moderate to large, short-period NNE (020 degree) swell, generated by a gale low northeast of the state will hold throughout the day today. Several reinforcing pulses will likely maintain surf near the borderline High Surf Advisory threshold for north facing shores through around Tuesday. Select east facing shores and west facing shores will also see elevated surf due to the northerly swell. Small Craft Advisory remains in effect for all Hawaiian Waters due to a combination of wave heights and strong trade winds.

Also, due to the NNE swell, a Marine Weather Statement for harbor surges remains in effect, particularly affecting Hilo and Kahului Harbors.

For other shorelines, surf along east facing shores will remain choppy and short-period due to the strong trade winds, with some areas also being exposed to the incoming NNE swell. South shores will continue to see small pulses from the southern hemisphere over the next few days. A storm-force low developing southeast of New Zealand over the next few days could send a moderate south- southwest swell the following week.

HFO WATCHES/WARNINGS/ADVISORIES

High Surf Advisory until 6 PM HST this evening for Niihau-Oahu North Shore-Olomana-Maui Windward West-Maui Leeward West-Kauai North-Kauai East-Koolau Windward-Molokai Windward-Molokai North- Maui Central Valley North-Windward Haleakala-Big Island East-Big Island North.

Small Craft Advisory until 6 PM HST this evening for all Hawaiian waters-