An increase of moisture from the remnants of Norbert will bring a wet trade wind pattern from late Wednesday through Friday. Deep tropical moisture combined with some instability will bring an increase of heavy rain especially over windward and mauka areas. Improving weather conditions are generally expected over next weekend, but some scattered showers will likely persist.
This evening's satellite imagery shows a band of moisture east of the Big Island, which will be moving east to west across the state on Monday. 00Z soundings from Lihue and Hilo show a stable trade wind inversion at around 6000 to 7000 ft. While stable conditions are expected to persist over the next few days, the increase of moisture will bring an increase of humidity and some light to moderate showers over windward and mountain areas. Dewpoints are expected to get into the 70s by late Monday into Tuesday, which will bring some muggy weather across the state.
Starting Wednesday and continuing through Friday, the weather pattern will change as the remnants of Norbert moves east to west across the state. Deep tropical moisture from Norbert combined with a weak upper level trough will bring an increase of heavy showers especially by Thursday. With trades picking up to moderate to breezy speeds by late Wednesday into Thursday, the focus of the heavy rain will be over windward and mauka areas. A Flood Watch may be warranted especially for Thursday into Thursday night, but we will wait to see what the high res models show as we get closer to the second half of the week. So overall we are expecting a wet, trade wind pattern during the second half of the week.
Over the weekend, while the bulk of the deep tropical moisture should move west of the state, some showery weather could linger through at least parts of Saturday. But generally improving weather conditions are expected this weekend with moderate to breezy trade winds.
The forecast remains on track as lighter and drier trade winds hold over the Hawaiian Islands tonight. Expecting shower activity to remain limited tonight into tomorrow thanks to these winds, with the windward side of the islands having a 15-40% chance for showers while the rest of the areas remain dry. Trade winds for tomorrow look similar in strength, perhaps a touch lighter, and that should allow for sea breezes to develop on the leeward side of the islands.
For PMDY conditions look to remain dry, though we may get a few low to mid level clouds due to a low sitting north of the region. Opted to keep the forecast dry for the site on Monday, though the ECMWF model shows the potential for some passing showers Monday afternoon. Both the GFS and the ECMWF show showers late Monday into Tuesday, with winds shifting to the north or northwest.
For NSTU, models show passing showers through the TAF cycle, which may bring periods of MVFR cigs and vis.
Clouds have decreased over Kauai, so likely will end the current AIRMET in effect for mountain obscuration. No additional AIRMETs are likely, but we'll continue to keep an eye out at reports and webcams should the reach mountain obscuration criteria for clouds and/or precip.
Issued at 306 PM HST Sun Sep 13 2026 Moderate trades will continue through the week before gradually strengthening through the latter half of the week. Moisture associated with a weak trough moving in on the trade wind flow may bring a slight uptick in shower activity to the coastal waters Tuesday into Wednesday. While the current forecast has Tropical Storm Norbert dissipating before it nears the Hawaiian coastal waters from the east, remnant moisture from this system is expected to arrive potentially by Thursday, likely bringing more showers.
Surf along south-facing shores will gradually decline through Monday as the small, medium-period energy slowly fades. A series of long-period swells are expected during the second half of the week. The first pulse will gradually fill in Tuesday into Wednesday out of the southwest, followed by larger south-southwest swells Friday into the weekend. Surf could get near advisory thresholds over the weekend, but at this time it looks like it would peak just below advisory thresholds.
Surf along east-facing shores should see an increase during the second half of the week as the trades strengthen and the remnants of Norbert moves through the islands. Flat to tiny surf along north facing shores is expected through the forecast period.
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