textproduct: Honolulu

SYNOPSIS

A surface ridge building north of the islands will allow moderate trade winds to return to the islands today. Rainfall will be limited into the weekend due to an upper level ridge over the islands. However low level moisture riding in on the trades will bring more typical windward and mauka showers by the end of the weekend.

SHORT TERM UPDATE

No major changes were made. Previous forecaswt remains on track.

PREV DISCUSSION

Issued at 338 AM HST Thu Apr 23 2026

In the very short term, we are in close contact with the Hawaiian Volcano Observatory with regards to Kilauea's episode 45 eruption which began not long after midnight. An Ashfall Advisory was recently issued for volcanic debris that may be reaching areas to the south to southwest of the volcano.

Otherwise, no significant change to the forecast with the morning package. The PoPs and supporting grids have been nudged to the latest National Blend of Models package.

A low pressure system roughly 700 miles east-northeast of the islands, combined with low about 1000 miles north-northwest of the islands are helping to disrupt the trade wind flow. However the low the east-northeast will continue to weaken today as it moves to the east away from the islands. And the low to the north-northwest will lift to the north. As this happens today, the ridge to the north will strengthen, and moderate trades will filter back over the islands. The global models agree on mid level ridging over the region which will help to maintain a stable airmass, thereby limiting rainfall totals over the next few days.

The global models are in good agreement that moisture from the above mentioned low will get caught up in the trade wind flow over the weekend, and late in the weekend, make its way into the islands. This will help us return to a more typical trade wind weather pattern with some showers over the windward and mauka areas, along with the clouds and showers that form over the Kona slopes during the afternoon.

AVIATION

Moderate trade winds will prevail over the islands over the next several days. VFR conditions are expected, with isolated showers and brief MVFR conditions possible for primarily windward and mountain sites. No AIRMETs in effect.

With an eruption of Kilauea underway, increased haze and ash around the southern half of the Big Island is highly likely. SIGMET series Yankee is in place with estimated ash tops at FL150.

MARINE

Issued at 338 AM HST Thu Apr 23 2026

Trade winds will be making a come back today in response to an upper ridge ever so slowly expanding in from west northwest of the islands. The associated surface high far northwest of the offshore waters will travel east, pass north of the local waters and be northeast of the area by early next week. This will produce a tight enough Central Pacific pressure gradient over the islands to maintain moderate to locally fresh trade wind magnitudes the next several days. Trades will persist through the weekend as another high passes north of the state. Brief periods of locally strong winds will be possible this weekend across the windier channels and bays surrounding Maui County and Big Island.

A small, short to medium period northwest swell that peaked yesterday will gradually level out the next few days. A pair of North Pacific gale lows will send a series of small north to northwest swells down into the local waters from Friday night through the first half of next week. These swells will maintain waist to head high surf along north-facing shores into next week.

An overlapping small, short to medium period north northeast swell that peaked yesterday afternoon introduced advisory level surf along many northeast to eastern exposures, as well as elevating surf to above average heights along select Maui and Big Island western shores. This swell has leveled out and fallen below levels that will not produce advisory level surf. Therefore, the High Surf Advisory for east facing shores has been cancelled. An enhanced northeast fetch in the proximity of a vicinity weak low northeast of the islands will push in a secondary swell tomorrow. Moderate to fresh trades will also support near seasonal average east-facing shore wind wave surf.

Small background energy from the west will continue to linger the next few days and fade out this weekend. A small southwest bump from Tasman Sea gale energy that passed across American Samoa's 51209 buoy yesterday is expected to arrive this weekend. No significant south swells are expected through the first half of next week.

HFO WATCHES/WARNINGS/ADVISORIES

Ashfall Advisory until 6 PM HST this evening for Big Island South-Big Island Southeast.