Swell Matrix

Area Forecast Discussion

National Weather Service Honolulu Hi

515 am hst Fri Sep 4 2026

Synopsis

A high pressure ridge to the north and Hurricane Lowell passing south of the Hawaiian Islands will keep breezy trade winds in the forecast today. Expect decreasing wind speed trends this weekend as a low pressure trough moving into the Central Pacific basin weakens the ridge north of the state. Periods of showers will favor windward mountain areas with brief passing showers over leeward zones. Hurricane Lowell will remain near major hurricane strength when it moves closer to the western Hawaiian Islands late Monday and Monday night. Weather impacts such as high surf and heavy rain may extend hundreds of miles from the center of Hurricane Lowell.

Discussion

Looking into the satellite imagery a long band of unsettled clouds with embedded showers are riding into the islands on the trade winds this morning. Periods of showers will continue to drift over the windward mountain slopes of each island through the morning hours. Elsewhere Hurricane Lowell roughly 600 miles south of Oahu and Kauai continues to drift slowly westward this morning. A gradual decrease in the forward speed of Lowell remains in the forecast for the next day or two, followed by a sharp turn to the north on Sunday.

Hurricane Lowell will remain near major hurricane strength when it moves closer to the western Hawaiian Islands late Monday and Monday night. There remains a risk for high surf, storm surge, strong winds and heavy rainfall impacts for portions of Hawaii including in particular the islands of Niihau and Kauai. Deep tropical moisture will advect northward across all island, producing warm and humid weather conditions with increasing heavy rainfall trends from Sunday into Tuesday as Hurricane Lowell turns northward. Initial storm total rainfall estimates range from 2 to 8 inches statewide with locally higher amounts of around 10 inches possible along terrain favored south and southeast slopes. Please continue to closely monitor the weather forecast for early next week as the track and associated impacts with Hurricane Lowell will likely evolve over time.

High pressure builds back over the islands from Tuesday afternoon onward as a wet trade wind pattern with periods of passing showers sets up across the state into the end of next week.

Aviation

Mostly VFR through the TAF period with the exception of passing MVFR showers favoring windward mountain areas through this morning. Moderate trades to breezy conditions into the afternoon with some sites gusting near 30 kts for wind favored locations after 20z Fri. Brief showers return after 08Z tonight with locally MVFR cigs.

Hurricane Lowell will continue to pass south of the island chain through Saturday. On this westerly track, regional trade winds will remain breezy per a tight pressure gradient between the hurricane and high pressure to the far north.

AIRMET Sierra remains in effect for mountain obscurations through later this morning for windward parts of the islands.

AIRMET Tango remains in effect for moderate low level turbulence south through west downstream of high terrain. AIRMET Tango will likely be in effect for the foreseeable future.

Marine

A surface high persists north of the Hawaiian Islands and will slowly drift east through the weekend. Currently, Hurricane Lowell is passing near 450 nm south of the islands as it continues to track west. The interaction between the two will strengthen the trade winds across the coastal waters to fresh to locally near gale force. A Small Craft Advisory (SCA) has been extended for all Hawaiian Waters through Saturday and will likely be extended.

The latest track from Hurricane Lowell from the National Hurricane Center is bringing Tropical Storm conditions to the far southern offshore waters. Although as Hurricane Lowell turns north, confidence is growing for hurricane conditions to the southwest and western offshore waters on Sunday. How close it gets to the state, is yet to be determined. As for Hurricane Karina, confidence is increasing that Karina will pass to the north and northeast of the state.

Swells from Hurricane Lowell are filling in and will remain elevated above High Surf Advisory (HSA) conditions through Saturday. A large, medium-period east swell from Hurricane Karina is filling in and will continue though the weekend, producing high end advisory level surf or warning level surf along east facing shores. The HSA has been extended in time and expanded to include east facing shores. The swell from Lowell will gradually veer from southeast towards the southwest early next week. While, the forecast for swells and seas for next week will highly depend on the eventual track and intensity of Lowell, confidence is beginning to increase for the potential of extra- large surf (exceeding warning levels) along south and western exposures early next week. Coinciding also with monthly high tides, this will create the potential for impacts to harbor entrances, channels, as well as coastal properties and infrastructure including roadways.

Watches, Warnings, Advisories

High Surf Advisory until 6 AM HST Saturday for south and east facing shores of all Hawaiian Islands.

Small Craft Advisory until 6 AM HST Saturday for all Hawaiian waters-

Visit this site often? Consider supporting us with a $10 contribution.
Learn more