textproduct: Honolulu

SYNOPSIS

Moderate to breezy trades today will continue to weaken through Thursday, allowing winds to decrease to moderate levels for the remainder of the week. Passing showers will be carried in on the trade wind flow at times, mainly over windward and mauka areas. While details remain very uncertain, a wet pattern is expected to develop towards the middle of next week.

SHORT TERM UPDATE

No big changes to the forecast philosopy this evening. As satellite imagery continues to show bands of unsettled clouds riding up over the island mountain slopes on the trade winds. Expect brief periods of showers to continue through the early morning hours under the influence of a weak upper low. These showers will favor the typical windward and mountain areas in the overnight to early morning hours.

Published a minor update to the forecast this evening; precipitation chances, weather, sky and precipitation amounts were tweaked a bit higher to account for the increased windward mountain shower activity.

PREVIOUS DISCUSSION

Issued at 328 PM HST Wed Oct 21 2026 This morning's satellite imagery shows scattered cumulus clouds across the state with some passing showers riding in with moderate to locally breezy trades. As the 1028 mb high continues to weaken and drift eastward over the next few days, the trades will weaken to moderate speeds by Thursday. Generally fair trade wind weather is expected Thursday and Friday, but some scattered showers riding in with the trade winds will be capable of producing some moderate showers mainly during the overnight and morning hours.

Over the weekend, we could see some showery weather at times from 2 subtle weather features. A weak trough currently southeast of the Big Island is expected to drift further northward, but the northward extent remains uncertain. Depending on how far north the moisture gets, we could possibly see some heavier showers develop over windward Big Island this weekend. The second feature is the remnants of an old frontal boundary riding in with the northeast trades and arriving over Kauai late Saturday and eventually making its way to around Oahu on Sunday. Some scattered showers should be expected, but rainfall intensity should range from light to moderate. The deeper moisture around the Big Island will be capable of producing some heavier showers Saturday afternoon into Sunday.

Beyond the weekend, the forecast remains very uncertain for next week. While confidence remains high on a wetter pattern developing around Tuesday or Wednesday of next week, the potential impacts remain very uncertain. Majority of the global models and its ensemble members show some type of low pressure system developing along a monsoon trough near 15N180W this weekend. The low is then expected to drift eastward but varies significantly on the position and intensity of the low among the various ensemble members. While we could begin to see some unsettled weather beginning as early as late Monday, the more impactful weather will likely be closer to Tuesday or Wednesday. Thus, I removed the threat of thunderstorms for Monday into Monday night. While the 18Z GFS ensembles are showing moisture moving in earlier than the ECMWF ensembles, there is some agreement in the deeper tropical moisture arriving late Tuesday into Wednesday. Please stay tuned to the forecast as we get more information on the potential heavy rain event next week. With deep moisture (precipitable water values well above 2 inches) moving in from southwest, the threat for heavy rain and flash flooding will be possible across the state.

AVIATION

Generally VFR across all island hubs through the entire period. A weak upper low over the state with vicinity surface troughs will create just enough instability, in tandem with ample lower level moisture, to maintain chances of prevailing VCSH and/or TEMPO SHRA with MVFR for lower ceilings over more windward-exposed terminals such as PHLI and PHTO.

No AIRMETS are in effect.

MARINE

A surface low pressure system far north of the Hawaiian Islands will dig southeast, becoming located due north of the state by Friday. This will push the high pressure that has brought consistent trades off to the east. Trades will weaken from Thursday into the weekend. Weak to moderate trades should continue into early next week, but low pressure developing west-southwest of the islands early next week will lead to a chance of southeast winds by Tuesday or Wednesday.

Tiny surf along north-facing shores will grow slightly tonight into Thursday and then remain steady Friday as a small northwest swell arrives. A slightly larger medium-period north-northwest swell will follow this weekend. A potential storm-force low developing north of Japan will likely send a larger long-period west-northwest swell early next week.

Surf along south-facing shores will remain small before a series of small to moderate, south-southwesterly swells boosts surf heights to near to above seasonal average this weekend into early next week.

East-facing shores will see trade wind swell decline through tonight as trade winds decrease, leading to a slight reduction in surf through the remainder of the week. A small, medium-period east swell originating from former Hurricane Trudy forecast to arrive Thursday may help maintain east-facing surf into the weekend.

FIRE WEATHER

Issued at 328 PM HST Wed Oct 21 2026

With the trades decreasing to moderate speeds by Thursday, fire weather concerns will remain at low to moderate. Mostly dry leeward conditions will likely persist through the weekend. The subsidence temperature inversion across the state will remain in the 7000-8500 ft range into Thursday and will be weakening as a weak trough drifts further north, east of the state. Widespread wetting rain will be possible towards the middle of next week.

HFO WATCHES/WARNINGS/ADVISORIES

None.