textproduct: Honolulu

SHORT TERM UPDATE

Unstable weather day expected today due to an upper level trough moving through the state. Expect showers to increase later this morning into the afternoon especially across Oahu, Maui County and the Big Island. Moderate to locally heavy showers will be possible and due to the slower storm motion, some localized flooding will also be possible today. Shower activity and the threat of heavy rain should diminish this evening into the overnight hours as land breezes develop. Over the summits of the Big Island, afternoon snow showers are expected and a Winter Weather Advisory has been issued.

SYNOPSIS

Moisture and instability will linger over the islands today, though will gradually decrease by the end of the weekend. Winds will weaken and veer east-southeasterly today, then become light and southerly on Sunday, allowing land and sea breezes to dominate and drive afternoon showers over interior and leeward areas. Forecast confidence decreases early next week as one or more weak fronts approach the state, though limited upper-level support should keep rainfall impacts modest.

PREV DISCUSSION

/ISSUED 356 AM HST Sat Jan 24 2026/

The 12z upper air soundings from Lihue and Hilo show that a moist and somewhat unstable air mass remains in place across the island chain early this morning as the inversion has eroded a bit compared to 24 hours ago. A late evening ASCAT pass revealed that light to moderate easterly trade winds have briefly returned to the state overnight as surface high pressure continues to slide eastward away from the state. Showers and low clouds during the past twelve hours or so have primarily favored windward and mauka areas, particularly for the island of Maui yesterday evening, and now predominantly Oahu early this morning. Meanwhile, ample moisture aloft is resulting in scattered high clouds moving across the region.

As high pressure continues to shift east ahead of the next front approaching from the northwest, winds are expected to gradually veer east-southeasterly today, then weaken further and turn southwesterly across the western half of the state by Sunday. As the winds decrease, this will set up a daytime sea breeze and overnight land breeze regime across the islands. Meanwhile, the upper-level trough that has been supplying instability will slowly move off to the east, allowing atmospheric stability to increase from west to east as mid-level ridging builds into the region. With that said, moisture and instability will linger today as the upper trough moves over and eventually past the region. This will keep showers in the forecast, and isolated thunderstorms have also been introduced across eastern portions of the island chain for the afternoon. Additionally, with cold temperatures and deep moisture over the summits, snow showers and freezing fog may emerge again this afternoon as daytime heating sparks convection over the Big Island.

By Sunday, instability and moisture will be decreasing, and confidence in thunderstorm chances remains too low to include in the forecast at this time. Isolated to scattered showers will still be possible over interior and leeward areas during the afternoon where sea breeze induced surface convergence commences.

An unusual amount of uncertainty exists in the forecast early next week, as global models still offer wildly different solutions regarding a potential front moving into or through the area. The ECMWF, for example, brings a front into the western part of the island chain by late Sunday night, then shows it quickly moving down the island chain on Monday. This scenario offers a wetter solution and breezy northeasterly winds following the frontal passage. Meanwhile, the GFS keeps the front north of the state, with the island chain remaining in a drier pattern with lighter winds persisting. In any case, even if the front does move into the islands, with mid-level ridging forecast to persist over the state, there would be limited upper-level support.

The rest of the week next week looks to remain fairly dry with light southeasterly winds returning for much of the week. This would once again favor a land and sea breeze regime ahead of another potential front towards the end of next week.

AVIATION... Isolated showers continue over the eastern islands with most locations remaining in VFR conditions. Easterly winds will remain light and gentle through the day and may veer to the southeast over the western end of the state by the afternoon. With the light winds, the chance for seabreeze and land breeze patterns may set up over interior sections of the islands. Drier conditions are expected as some MVFR cigs/vsbys may affect interior portions of the islands in the afternoon but predominantly VFR conditions are expected statewide.

Currently, no AIRMETs are effect.

MARINE... A high pressure system currently north of the state will drift eastward over the weekend as another front approaches the state from the northwest. Moderate trades will veer from a more southeasterly direction today, then become light southerlies from tonight into Sunday. Winds should become light enough for near shore land and sea breezes to develop during this time. The tail end of the cold front will likely move into the northwest waters late Sunday into Monday with fresh north to northeast winds blowing in north of the front. There are still some uncertainty on how far southeast the front will move into the islands, which will alter the reach and extent of both northerly winds and rain showers over island waters. Highest chances are that the forward motion of this weak cold front stalls out near Kauai waters by Monday morning.

The current medium period north-northwest (330-340 degree) swell will continue to decline today. Surf heights will remain elevated as a series of small overlapping northwest swells will pass through the Hawaii region through the weekend into early next week. The first pulse should arrive late Saturday and peak on Sunday, followed by another pulse late Monday. A slightly larger north-northwest (330 degree) swell is expected Tuesday into Wednesday. In the long range, there is potential for a large long period northwest swell building to warning levels impacting north and west facing shores towards the end of next week.

Surf along east facing shores will remain small into next week due to the lack of persistent trade winds locally and upstream. South facing shores will remain nearly flat through the weekend. A tiny long-period south-southwest swell may produce a slight boost to south shore surf heights from late Sunday into Tuesday.

HFO WATCHES/WARNINGS/ADVISORIES

Winter Weather Advisory from noon today to 6 AM HST Sunday for Big Island Summits.