textproduct: Honolulu

SYNOPSIS

Light to moderate trade winds are expected through the weekend. Brief passing showers will move into windward and mountain areas on the northeasterly trade winds, favoring the overnight to early morning hours. A more significant change to our weather pattern continues to evolve for next week. Deeply unstable tropical moisture moving across the state will bring the potential for heavy rain and thunderstorms to most islands starting around Monday night or Tuesday and persisting through at least the middle of the week.

SHORT TERM UPDATE

Satellite and radar imagery show mostly sunny conditions across the smaller islands this morning, with isolated showers moving in on the light to moderate northeasterly trade wind flow. Also evident on satellite imagery is a surface trough just east of the state this morning, with the leading edge of its large plume of moisture moving into south- and east-facing portions of the Big Island. This feature is expected to bring increased cloud cover and scattered showers to windward portions of the Big Island and Maui through tonight before the trough gradually pushes off to the east, pulling this moisture away from the state. The current forecast remains on track, so no changes were made with this morning's update.

PREV DISCUSSION

Issued at 533 AM HST Fri Oct 23 2026

The trade winds have eased to become light to moderate in response to the weakening pressure gradient as the surface high gets pushed farther northeast of the state and a low pressure system sets up to the north. As this low continues to drift southeastward, high pressure will build behind and will allow the northeasterly trades to gradually strengthen through the weekend. Moderate trades are expected later this afternoon and could become locally breezy in a few areas this weekend as the remnants of a dissipating frontal boundary moves into Kauai on Saturday and over Oahu on Sunday. An increase of trade wind showers should be expected as the old frontal boundary moves through this weekend.

Also a weak trough southeast of the Big Island could bring an uptick of moisture over windward Big Island this weekend. Brief downpours will be possible, especially over the windward slopes during the afternoons.

Starting next week, a very unusual weather pattern is expected to develop over the state. A surface low is expected to develop near 15N and the international dateline this weekend. This low pressure system will gradually track eastward next week. While tracking eastward, a deep upper level trough will develop just west of the state and will transport a broad area of deep tropical moisture (with precipitable water values of up to 2.5 inches) over the state around Tuesday and Wednesday of next week. While there are still some timing differences, there is potential for significant heavy rain and flash flooding towards the middle of next week. Due to the broad band of deep moisture, it is going to be difficult to pinpoint what areas will be impacted the most and will highly depend on where the clusters of thunderstorms develop. While, heavy rain and flash flooding will be the main concern, some damaging winds will be possible with any thunderstorms.

AVIATION

A strong jet stream just to our north is forecast to shift southward and could produce severe turbulence in and close to SIGMET Romeo. Light to moderate turbulence is possible around Kauai and Oahu between 24 and 32,000 feet.

Lower level isolated moderate turbulence is also possible under 10,000 feet. While no AIRMETs are currently in effect, AIRMET Tango will be considered later today for this local turbulence threat.

Light trade winds will continue across most of the terminals where VFR conditions will prevail. PHTO will likely see passing showers later today which could produce brief MVFR ceilings and visibilities.

MARINE

A surface low far north of islands will move to the southeast through Saturday and will stall roughly 800 nm northeast of Oahu Sunday and Monday, keeping the subtropical ridge just north of the area rather weak. Trade winds will be at gentle to moderate strength during much of this time, though a brief period of fresh northeast winds may accompany a shallow band of showers moving over Kauai and Oahu Saturday night. Uncertainty increases Tuesday, when an area of low pressure is expected to move over the islands from the southwest, bringing variable winds and the potential for heavy showers and thunderstorms.

Small surf will persist along north shores into Saturday. A moderate, medium-period north-northwest swell will build late Saturday and produce surf near seasonal average during its peak on Sunday. As this swell declines on Monday, a long-period west- northwest swell will arrive, maintaining small to moderate surf into the middle of next week.

Small background level surf will prevail along south-facing shores into Saturday. A series of small, overlapping, medium- period south-southwest swells will push surf back to near seasonal average late Saturday into early next week. A larger south-southwest swell is possible Thursday.

Along east-facing shores, wind swell energy will be low through much of the week, but a small medium-period northeast swell may maintain small surf through Saturday. Aside from wrapping north- northwest swell in exposed areas, east shore surf should remain below seasonal average.

FIRE WEATHER

Issued at 533 AM HST Fri Oct 23 2026

Moderate trade winds with mostly dry conditions over leeward areas will continue to produce low to moderate fire weather conditions through the weekend. Ample tropical moisture will move in from the southwest sometime beginning Monday night or Tuesday, bringing a threat for heavy rain through the middle of the week. As a result, fire weather concerns will be low next week. Inversion heights will range from 6,000 to 8,000 feet today and will be relatively weak over the eastern end of the state due to a weak trough southeast of the Big Island.

HFO WATCHES/WARNINGS/ADVISORIES

None.