textproduct: Honolulu

SYNOPSIS

A plume of moisture moving in from the southeast is causing and increase in showers over the eastern half of the state this evening. This moisture will continue to spread westward into Tuesday. Due to the abundant moisture, brief periods of heavy rain will be possible. Also the increase of humidity could make tonight feel warmer than usual. Our more typical trade wind pattern will return on Wednesday.

SHORT TERM UPDATE

Some minor adjustment made to PoP, otherwise previous forecast is on track.

PREV DISCUSSION

Issued at 406 PM HST Mon Jun 1 2026

A weak surface trough moving in from the southeast will bring an increase of showers as this moisture moves east to west tonight through Tuesday. Latest sounding from Hilo and Lihue shows the moisture gradient with values of over 2 inches at Hilo and 1.3 inches at Lihue. Showers will be increasing over Maui County this afternoon and tonight and spread towards Oahu and Kauai tonight into Tuesday. With the moderate trade winds in place, showers will generally focus over windward and mauka areas. But due to some southeasterly flow in the lower levels, some leeward areas should also see some scattered showers. While the instability remains lackluster, the abundant moisture should provide some brief periods of some locally heavy rain during the next 24 to 36 hours.

By Wednesday afternoon, the plume of moisture should be west of the state with drier air moving in from the east. Trades are expected strengthen towards the end of the week with breezy to locally strong trades expected around Friday. Precipitable water values remain near normal or slightly below normal for the second half of the week, which should translate to our typical windward and mauka showers, primarily during the nights and early morning hours.

AVIATION

A surface trough near the islands will continue to enhance shower activity across the state. Showers are expected to become more widespread early Tuesday morning, with MVFR and even brief IFR conditions possible within heavier showers. Rain chances are expected to relent during the latter half of Tuesday. Winds will remain primarily easterly.

AIRMET Sierra for mountain obscuration is in effect for windward Maui, Molokai, Lanai, and the Big Island. This may need to be expanded overnight as showers move over other islands.

AIRMET Tango is in effect for moderate turbulence between FL310 and FL370 due to an upper level disturbance. This is expected to weaken and diminish overnight tonight.

MARINE

Issued at 406 PM HST Mon Jun 1 2026

High pressure far northeast of the Hawaiian Islands will strengthen through Wednesday, then shift north of the islands through the remainder of the week. A scatterometer pass earlier today showed that strong winds had developed through the typical channels and waters in the vicinity of the Big Island. As a result, a Small Craft Advisory (SCA) has been issued for the typically windier waters around Maui County and the Big Island. High resolution guidance suggests that these winds are likely to stick around, especially with the broader-scale trade winds continuing to intensify in response to strengthening ridging north of the islands this week. This will likely necessitate expansion of the SCA into the windward waters and further along the island chain within the next few days.

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. Long-period forerunners from a new south-southwest swell are steadily filling in, which is expected to bring surf back to advisory levels by Tuesday morning. A second long-period south-southwest swell arriving tonight will likely push surf above the advisory threshold as the swell peaks on Wednesday. A gradual downward trend is then expected for the latter half of the week.

Surf along north-facing shores will see a small uptick on Tuesday, with a (relatively) larger swell arriving Wednesday night, bringing small surf Thursday into Friday from a broad gale far north of the state near the Aleutian Islands.

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

High Surf Advisory from 6 AM Tuesday to 6 AM HST Thursday for Big Island South-Big Island Southeast-East Honolulu-Ewa Plain- Honolulu Metro-Kahoolawe-Kauai South-Kauai Southwest-Kona-Lanai Leeward-Lanai South-Maui Central Valley South-Maui Leeward West- Molokai Leeward South-Niihau-South Haleakala-South Maui/Upcountry-Waianae Coast.

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