textproduct: Honolulu

SYNOPSIS

A high pressure system will linger north of the Hawaiian Islands producing moderate to breezy trades through the middle of next week with minor fluctuations in speed. Brief pulses of enhanced showers will roll through on the trades during this time period, with showers favoring windward mountain areas in the overnight to early morning hours.

SHORT TERM UPDATE

The first of three easterly waves is moving through the islands tonight enhancing showers statewide with the highest rainfall amounts forecast along the windward mountains of each island. Two additional easterly waves are clearly shown on satellite imagery that will bring another round of increasing shower trends from Sunday into early next week.

The afternoon forecast grids look good, no evening updates.

PREVIOUS DISCUSSION

Issued at 332 PM HST Fri Oct 16 2026 Radar and satellite imagery show isolated to scattered showers moving into mainly windward and mauka areas of the state this afternoon, with shower coverage increasing over the eastern half of the state as a plume of deeper moisture moves in on the weakly convergent trade wind flow. This uptick in windward shower activity will work its way up the island chain and persist into the evening hours before drier air fills in on Saturday.

Surface high pressure to the north will build through the weekend and strengthen the trade wind flow to breezy levels through early next week. Additional batches of increased moisture will continue to filter in on the trades over the next several days and bring brief upticks in windward and mauka shower activity, particularly during the overnight to early morning hours. Overall, these showers may produce brief moderate downpours at times, but they will move through rather quickly, so flooding is not expected to be an issue.

Both aloft and at the surface, broad and weak troughing will gradually develop over the Central Pacific by midweek, weakening the pressure gradient and therefore decreasing the trade wind speeds. Otherwise, periodic showers will continue to filter into windward and mauka areas on the weakening trade wind flow.

By next weekend, models are hinting at more substantial instability developing aloft and a larger area of deep tropical moisture being drawn up from the southeast, possibly leading to the potential for widespread heavy showers. However, the window with the greatest potential for any impacts is beyond the forecast period and with the model discrepancies that far out, forecast confidence is on the lower side for that period.

AVIATION

Moderate to breezy trades through the period. Low cigs and SHRA should impact windward and mauka locations with some limited spillover to leeward areas. Isol IFR to MVFR conds possible in SHRA, otherwise VFR prevails.

AIRMET Sierra is in effect for mtn obsc for portions of all islands due to cld and SHRA. Conds should improve in the mid morning hours.

AIRMET Tango is in effect for mod turb lee of terrain. Expect this continue for a few days.

MARINE

High pressure north of the islands maintains fresh to strong trades well into next week. The Small Craft Advisory remains in effect for the typically windy waters around Maui County and the Big Island.

A medium-period NNW swell peaks tonight in maintenance of seasonable surf along N shorelines. This swell has been slow to arrive with NDBC 51001 buoy still observing short period swell in the 5 to 6 foot range. This swell will slowly decline and shift to the N during weekend as a smaller overlapping NW swell moves through the area. Both swells lower on Monday and fade on Tuesday. Another small NW swell is possible next Thursday or Friday.

S shore surf remains seasonable as long period swell peaks this evening then gradually declines this weekend. Surf along S shores then holds below average through next week.

Surf along E shores increases this weekend as trades strengthen. In addition, expect some wrap of NNW swell for exposed shorelines through at least Saturday. Rough trade wind swell will produce above average surf for E shores through Tuesday before declining with weakening trades mid-week.

FIRE WEATHER

Issued at 332 PM HST Fri Oct 16 2026 Surface high pressure far north of the islands will produce moderate to breezy trade winds for the next few days, with gradual strengthening expected through early next week. Between batches of showers rolling through on the trades, RH levels may approach critical fire threshold ranges, particularly Saturday afternoon. Otherwise, RH levels should help to maintain low to moderate fire weather concerns.

Inversion heights should increase to around 10,000 feet through tonight as the current batch of deeper moisture rolls through, then drop to 5,000 to 7,000 feet on Saturday.

HFO WATCHES/WARNINGS/ADVISORIES

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