textproduct: Honolulu

SYNOPSIS

A plume of moisture moving in from the southeast will bring increasing showers starting with the eastern half of the state today and spreading over the western half of the state tonight and continuing through Tuesday. Due to the abundant moisture, brief periods of heavy rain will be possible. Our more typical trade wind pattern will return on Wednesday.

UPDATE

Due to the abundant moisture moving in from the southeast over the next 24 to 36 hours, I have updated the forecast to generally increase POPs across the state. While the latest high-res models including the HREF and REFS continue to show the greatest precipitation over windward and southeast Big Island, some localized heavy rain will be possible over windward and mauka areas for the rest of the state especially tonight into Tuesday.

Also, an Ashfall Advisory remains in effect for episode 48 of the Kilauea eruption. Locations of the tephra fallout will vary today due to the variable wind directions throughout the atmosphere. Surface winds will generally be out of the northeast to east, but winds at 10,000 ft will generally be out of the southeast to south, and winds above 25,000 ft will generally be out of the west.

PREV DISCUSSION

Issued at 308 AM HST Mon Jun 1 2026

Latest satellite and radar imagery show a short-wave thats near overhead or just to the northeast of the island chain and sagging southward. Low clouds are moving across the islands within the trade wind flow. Radar imagery shows scattered showers ongoing across the islands, mostly impacting windward and mauka locations with some limited spillover to leeward areas. Some heavier showers are impacting windward Big Island causing some minor flooding or ponding on roadways and low-lying flood prone areas.

As the aforementioned shortwave continues advancing through the area, increasing showers will be most pronounced over the eastern end of the state today then expand up the island chain by Tuesday. Trades back northeast and strengthen to moderate levels during the early portion of the week, focusing showers windward and mauka. Breezy trades then establish during the second half of the week as the subtropical ridge strengthens north of the area.

AVIATION

An upstream trough will continue to bring periods of MVFR low clouds and showers to windward mountain areas of most islands. Some spillover showers into leeward areas is also possible. Pulses of wet weather continue across the Hawaii region for the next few days.

AIRMET Sierra remains in effect for mountain obscuration above 2000 feet for Oahu, Maui, and Big Island.

AIRMET Tango is in effect for moderate turbulence between FL300 and FL370 caused by an upper level disturbance. This is expected to diminish by the end of the day.

A volcanic ash SIGMET under series XRAY has been issued to cover the ash plume from Kilauea's most recent eruption. An ashfall advisory is also in effect for portions of the Big Island nearby the volcano.

MARINE

Issued at 308 AM HST Mon Jun 1 2026

Light to moderate trade winds will persist today, then gradually strengthen into the fresh to locally strong category Tuesday through the latter half of the week as the subtropical ridge builds north of the state. Small Craft Advisory conditions will likely develop in the typically windier channels and waters around Maui County and the Big Island beginning Tuesday.

Surf along exposed south-facing shores will remain elevated this week as a series of overlapping south to south-southwest swells move through the region. The current south swell, which peaked over the weekend, is slowly easing, with the peak energy down into the 14-15 second band. Long-period forerunners from the new south-southwest swell will steadily fill in today, leading to a building trend by tonight.

Surf is expected to return to advisory levels tonight through Tuesday and likely rise above the advisory threshold by midweek as the swell peaks. While some of the peak energy may have missed the PacIOOS American Samoa buoy to the east over the weekend, observations suggest surf heights should peak locally near, or possibly just below, the High Surf Warning threshold of 15-foot faces along south-facing shores around Wednesday. A gradual downward trend is then expected through the latter half of the week.

Surf along north-facing shores will increase Tuesday and remain up through Friday as a pair of overlapping northerly swells arrive from a broad gale far north of the state near the Aleutian Islands. Seasonal surf conditions should return by the weekend.

Surf along east-facing shores will gradually build by midweek as strengthening trade winds generate increasing short-period wind waves. Surf should return to near seasonal levels by the end of the week.

HFO WATCHES/WARNINGS/ADVISORIES

Ashfall Advisory until noon HST today for Big Island East-Big Island Southeast.