Area Forecast Discussion

SYNOPSIS

Light to moderate trades will strengthen through Wednesday. Moisture from the remains of Norbert should move through the islands Wednesday night through Friday morning as trades strengthen to moderate to fresh levels. Drier air will move back in this weekend as trades continue.

SHORT TERM UPDATE

Isolated showers were detected by radar across windward areas on Maui, Molokai, and Big Island this evening. A significant area of showers was offshore of Big Island north of Hilo, but it looks like it will remain offshore. Otherwise, trade winds were averaging 5 to 15 mph. Winds are still forecast to increase in the coming days as we prepare for a wet period from late Wednesday into early Friday. Latest models continue to show the possibility of heavy rain through that period. No changes are needed at this time.

PREV DISCUSSION

Issued at 405 PM HST Mon Sep 14 2026

Visible satellite shows mostly cloudy skies and scattered light showers over and upstream of the Big Island due to an area of tropical moisture moving in with the trade wind flow. Elsewhere, partly cloudy skies persist around the state with gentle to moderate trade winds. Expect the batch of clouds and showers to slowly track westward tonight into Tuesday night before exiting to the west. Rainfall amounts will not be significant, but a noticeable boost in humidity will occur.

We then turn attention towards the remnant of Tropical Storm Norbert, which is is expected to become post-tropical on Tuesday. Norbert has the potential to bring heavy rain, isolated thunderstorms and high humidity from late Wednesday night through Friday morning, though wind and surf will not pose any threat.

Trades will strengthen to moderate to breezy speeds by late Wednesday into Thursday, the focus of the heavy rain will be over windward and mauka areas, but leeward areas are likely to see impacts from the rain as well. A Flood Watch may be warranted especially for Thursday into Thursday night, but we will wait to see what the high res models show as we get closer to the second half of the week.

Over the weekend, while the bulk of the deep tropical moisture should move west of the state, showery weather could linger through at least parts of Saturday. But generally improving weather conditions are expected this weekend with moderate to breezy trade winds.

AVIATION

Moderate trade winds will continue into Tuesday, then gradually strengthen to become locally breezy Tuesday afternoon into Tuesday night. Moisture along a dissipating surface trough moving over the eastern end of the state this evening will move up the island chain through the day on Tuesday and increase windward cloud and shower coverage as it passes through. MVFR conditions are possible especially over the eastern end of the state where there is greater shower coverage. Otherwise, generally VFR conditions will prevail.

AIRMET Sierra is in effect for tempo mountain obscuration for the Big Island and may be needed through Tuesday morning as showers linger.

MARINE

Issued at 405 PM HST Mon Sep 14 2026

Moderate to locally fresh trade winds will persist through Tuesday as a weak trough lingers to the northeast. By Wednesday, building high pressure will increase the trade winds into the fresh to locally strong range through the weekend. Also by Wednesday afternoon, the remnants of Norbert will move through as a trough and increase shower coverage over Hawaiian waters.

Small surf along south-facing shores will continue through Tuesday before a series of long-period S to SSW swells are expected to arrive Wednesday through the weekend. The first pulse will gradually fill in tonight into Wednesday out of the southwest, followed by larger south-southwest swells Friday into the weekend. As a result of these swells, surf will gradually trend upward through the week beginning Wednesday and could approach advisory thresholds by the weekend.

Surf along east-facing shores should see an increase during the second half of the week as the trades strengthen and the remnants of Tropical Storm Norbert move through the islands. Flat to tiny surf along north facing shores is expected through the forecast period.

FIRE WEATHER

Issued at 405 PM HST Mon Sep 14 2026

Fire weather risk will remain low the next several days due to light to moderate winds and the effects of recent rainfall. Inversion heights should be 6000 to 7000 ft through Tuesday. Moisture increases Thu/Fri, and should bring enough showers to keep things relatively wet.

HFO WATCHES / WARNINGS / ADVISORIES

None.