textproduct: Honolulu

SYNOPSIS

A relative decrease in shower activity in the wake of a departing surface trough associated with the remnants of Norbert is expected through this weekend. Moderate to locally breezy trade winds will continue through Monday before gradually declining by midweek. Another round of enhanced moisture will arrive by next Tuesday, which should increase shower activity statewide.

SHORT TERM UPDATE

No major updates were made as the previous forecast is on track.

PREV DISCUSSION

Issued at 319 PM HST Fri Sep 18 2026

This afternoons visible satellite and radar imagery shows a limited amount of shower activity relative to the past couple of days. A surface trough associated with the remnants of Tropical Cyclone Norbert continues to move westward as it exits the vicinity of the state tonight. However, an upper level trough combined with the residual moisture from Norbert has kept the environment relatively unstable, as noted by some thunderstorms occurring offshore earlier today, and over the Kona slopes of the Big Island this afternoon.

An increasing trend in stability and relatively drier air will begin this weekend, which will limit shower activity and coverage to windward and mauka areas. Kona slopes of the Big Island may still see some afternoon showers as well through the weekend, with a small chance of thunderstorms upslope due to lingering instability. However with the low confidence, have not added thunderstorms to the forecast. Trade winds will continue to blow out of the ENE-E direction at moderate to locally breezy speeds through Monday, but are expected to gradually decline by midweek.

Another influx of moisture associated with the remnants of Tropical Depression 15-E is expected to arrive by Tuesday and potentially remain through Thursday. Precipitable water values could reach up to 2.5" over the southeastern portion of the state according to global models, which is above seasonal normal. A shortwave is also expected to be within the vicinity of the islands during this time period, which could lead to some enhanced showers statewide.

The long term forecast will also be dependent on how models handle the remnants of Tropical Depression 15-E. The National Hurricane Center continues to monitor the situation, and suggests that environmental conditions are conducive for some development of the system next week. Given that there is plenty of time for this forecast to change, please continue to monitor the status of tropical cyclone development through nhc.noaa.gov, and local weather forecasts at weather.gov/hfo.

AVIATION

A surface trough associated with the remnants of former TC Norbert will exit the region to the west tonight. As a result, a drier trade wind pattern is expected on Saturday. VFR conditions will prevail for most locations, with the potential for passing MVFR ceilings and isolated showers mainly along windward and mountain areas. The Kona slopes of the Big Island could see some afternoon showers as well on Saturday. Isolated thunderstorms cannot be completely ruled out for the Big Island again on Saturday afternoon, but confidence is too low to include in the forecast at this time. Breezy trade winds will persist through the weekend.

AIRMET Tango has been issued for moderate low-level turbulence downwind of island terrain due to the breezy trade winds. This AIRMET will likely be needed through much of the weekend.

MARINE

High pressure will remain to the northeast, therefore moderate to locally strong trade winds will continue through at least the first half of next week. A Small Craft Advisory is in effect for the typical windy waters around Maui County and Big Island through Saturday, and will likely be extended into early next week for these waters. A trough could move into the area next week.

Surf along south-facing shores will remain above average through the weekend as long-period south-southwest swell peaks tonight. Then another south swell will build in Saturday and both swell will decline gradually next week. A smaller long period swell could fill in late next week.

Moderate surf along east-facing shores will persist over the next several days as fresh to locally strong trades continue. Surf along north-facing shores will remain flat to tiny, with a minor bump possible Tuesday into Wednesday next week. Then a small long period west-northwest swell swell could build in late next week.

HFO WATCHES/WARNINGS/ADVISORIES

Small Craft Advisory until 6 PM HST Saturday for Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters- Maalaea Bay-Pailolo Channel.