textproduct: Honolulu

SYNOPSIS

A high pressure system will linger north of the Hawaiian Islands producing moderate to breezy trades through the middle of next week with minor fluctuations in speed. Brief pulses of enhanced showers will roll through on the trades during this time period, with showers favoring windward mountain areas in the overnight to early morning hours.

SHORT TERM UPDATE

This morning's eruption of Kilauea ended at 9:03 AM HST. Therefore the ash cloud should end shortly. Otherwise, isolated windward and mountain showers continued across each island. These should decrease as they continue into the afternoon, and will be joined by Kona showers. Moderate to breezy trades will be with us for at least the next several days. All this is handled well by the current forecast, and no changes are planned at this time.

PREV DISCUSSION

Issued at 326 AM HST Sat Oct 17 2026 This mornings satellite imagery shows the first of three easterly waves continues to slowly drift through the islands enhancing shower activity through the early morning hours. Two additional weak atmospheric waves will drift from east to west across the islands on Saturday evening, and from late Sunday into Monday. Cloud and shower coverage will increase with each passing wave, favoring the overnight to early morning hours with the highest rainfall amounts falling over the windward mountain areas of each island. A wet trade wind pattern for sure with pulses of showers affecting each island through Monday.

A brief drying trend will develop by Tuesday as the last of the easterly waves passes to the west of the state. Subsidence aloft will lower temperature inversion heights with more stable trends reducing clouds and shower activity lasting through Wednesday. Expect the typical brief passing showers during the overnight hours over the windward mountain areas.

The long range forecast remains fairly uncertain as global models continue to struggle in finding a consistent solution with a passing short wave mid latitude trough passing just north of the Hawaiian Islands. The model solutions have flipped over the past few days with the American (GFS) model now showing a drier high pressure ridge setting up north of the island chain, and the European (ECMWF) model showing a cold core low, cut off from the mid latitude westerly winds, deepening just north of the state. The ECMWF solution would bring southeasterly to southerly winds over the islands, drawing up unstable tropical moisture from the deep tropics and triggering a period of wet weather across the islands. While the American GFS model shows more typical easterly trade wind weather with brief passing shower activity. Unfortunately these large scale differences are impossible to blend and we will have to wait a bit longer for our global weather model solutions to converge on a more consistent solution. Stay tuned for changes to the long range forecast.

AVIATION

VA SIGMET November in effect for Mt. Kilauea eruption in the south-central portions of Big Island. SEE VA SIGMET November for more detailed information. Expect this to continue until the eruption subsides, but based on overall wind trajectory, no ash threat near terminals is expected.

Otherwise, breezy trades will continue with isolated MVFR ceilings and visibility in any passing shower, mainly windward and mountain areas.

AIRMET Sierra was cancelled this morning as visibility has improved.

AIRMET Tango will continue today for tempo moderate turbulence downwind of terrain below 9000 ft.

MARINE

High pressure north of the islands maintains fresh to strong trades well into next week. The Small Craft Advisory (SCA) remains in effect for the typically windy waters around Maui County and the Big Island and the Kaiwi Channel. The SCA will likely be further expanded in areal coverage later today as trades undergo modest strengthening.

A short period NNW swell peaked at the outer buoys early this morning, and could provide a small boost to north shore surf this afternoon. This swell is also combined with gradually declining mid- long period swell (12 to 16 seconds) and will keep small surf in place through tomorrow. Both of these swells drop off by Monday, allowing surf to drop to tiny levels through much of the week before a small northwest arrives Thursday.

A mid to long period south-southwest swell (15 seconds) will keep above average surf in place today over south shores, then decline tomorrow and remain small through much of the week with background south swells. A small long period swell is possible next weekend.

Rough trade wind swell will produce above average surf for E shores through Tuesday before declining with weakening trades mid- week. Expect some wrap of NNW swell for exposed shorelines through at least today

FIRE WEATHER

Issued at 326 AM HST Sat Oct 17 2026 Fire weather conditions will remain below critical fire thresholds into the first half of next week. Breezy winds and minimum humidity levels will not align to reach critical levels in any of our fire weather zones. The subsidence inversion heights near Maui and the Big Island will range from 9,000 to 10,000 feet elevation today.

HFO WATCHES/WARNINGS/ADVISORIES

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