textproduct: Honolulu

SYNOPSIS

Trade wind weather will continue through the weekend with brief passing showers favoring windward and mountain areas of all islands. Winds begin to shift out of the south from Sunday night into Monday as a strong cutoff low pressure system approaches from the northwest. Strong southerly winds will draw deep tropical moisture northward increasing the threat for widespread heavy rainfall and severe weather through much of next week.

DISCUSSION

Issued at 300 PM HST Fri Mar 6 2026

Satellite shows increasing high clouds moving in from the west, along with the typical trade-wind cumulus at lower levels moving from ESE to WNW. Radar shows scattered to numerous light showers, mainly in windward and mountain areas. General low level wind flow was from the ESE, with terrain altering that flow in most leeward areas. Showers are expected to continue, and even become slightly more numerous, tonight.

We still see a significant weather system reaching the western end of the main islands Monday into Monday night, then extending eastward to all islands by Wednesday or Thursday. The potential for heavy rain, flooding, thunderstorms, and strong winds will last into next weekend for at least part of the state.

Models (deterministic and ensemble) are in fairly good agreement, especially considering the time frame involved, on the overall evolution of this event. High-over-low blocking patterns will become established both to our east and northwest this weekend. The closed upper level low to our northwest will strengthen and then remain in roughly the same area all next week. Even though this feature is over 1000 miles away, it will be the dominant factor in our weather next week. The low level circulation that forms beneath this upper feature will switch our winds to southerly. This will draw moisture northward, increasing our PW values from current levels of just over one inch to just over 2 inches.

Cold air aloft will help destabilize the atmosphere, and we will likely see thunderstorms over parts of the area from Tuesday into next weekend. Several shortwave troughs are likely to rotate around the closed upper low and then move toward/over the state next week. As they do, winds will increase at all levels, increasing advection of moisture and providing shear that aids the formation of strong showers and thunderstorms. At this time, the most significant of these shortwaves is forecast to move through the state Wednesday or Thursday. However, "lesser" shortwaves, impossible to exactly time, will still have the potential to bring heavy rain and gusty winds along with the accompanying showers and thunderstorms.

Timing: the western end of the state may be impacted as early as late Monday into Monday night, with the threat spreading east over the entire state Tuesday into Wednesday. The threat will then linger into next weekend due to the blocking pattern referenced above. The pattern just isn't expected to change much. Models show a significant flow of moisture over the state the entire time, and it may even extend beyond next weekend.

There are many details that will only become discernible when we get closer in time (exact timing of shortwave troughs, for example), so please stay up to date as this event approaches. When the stronger parts of the system move through, the potential for flash flooding is appearing more likely with each new model run. This is an unusually long-lasting system, and impacts are likely to stack up over time as the ground becomes saturated by repeated rains.

AVIATION

Issued at 300 PM HST Fri Mar 6 2026

East-southeast are beginning to pick up this afternoon and will continue to do so for the next 24 to 48 hours. VFR will prevail today, with brief periods of MVFR possible along east and southeast facing slopes due to low clouds and intermittent light showers moving in on the winds. No AIRMETs are currently in effect nor expected through the period.

MARINE

Issued at 300 PM HST Fri Mar 6 2026

Fresh to strong east to southeast winds associated with a surface ridge extending southwest into the region will remain in place through the weekend. Expect the strongest winds and roughest conditions within the channels, along the Hamakua Coast of the Big Island, windward waters, and south of the Big Island. A Small Craft Advisory has been expanded and extended to add the Kaiwi channel and Oahu windward waters through Saturday night. As the surface ridge begins to weaken early next week, a broad low pressure is expected to develop nearby to the west. This pattern will cause winds to veer out of the south to south- southeast, potentially remaining in the fresh to strong range next week.

Surf along east facing shores will elevated and choppy into early next week due to a large upstream fetch of fresh to strong breezes extending across the northeast Pacific. A downward trend is expected next week as this pattern weakens and local winds veer southerly.

Surf along north- and west-facing shores will remain relatively small through the period, with only a few west-northwest pulses expected over the weekend. A small medium period west-northwest (300 deg) swell is expected to slowly fill in Saturday and peak Sunday near head-high levels. A small long-period westerly (290 deg) swell associated with a slow- moving storm- force low tracking eastward toward the Date Line from the far northwest Pacific is expected early next week. However, the westerly winds associated with this system near the islands are forecast to weaken by the weekend, which will limit the amount of swell generated toward the state. Additionally, Kauai will block some of this energy from reaching other coasts across the island chain.

Surf along south-facing shores exposed to southeast trade-wind seas will gradually increase through the weekend. Conditions could become rough early next week as winds veer southerly and strengthen. A long-period south-southwest swell associated with a recent system passing through our swell window near New Zealand is expected to arrive Tuesday and persist through midweek.

HFO WATCHES/WARNINGS/ADVISORIES

Small Craft Advisory until 6 AM HST Sunday for Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters- Big Island Windward Waters-Kaiwi Channel-Maui County Leeward Waters-Maui County Windward Waters-Oahu Windward Waters-Pailolo Channel.