Marine Weather and Tide Forecast for Ko Olina, HI

SHORT TERM UPDATE
Showers were moving across most of Kauai and Niihau this morning, with mainly windward and mauka showers over Oahu and the islands of Maui County. Winds were mostly northeast at 5 to 15 mph, with occasional gusts of 20 to 25 mph in the typical windier locations.
We have done a small update this morning to increase the chance of showers for the remainder of today in most areas, especially on Big Island. The inversion height at Hilo this morning was around 11,000 feet, and we expect showers well up the mountains this afternoon. Trade winds are still expected to continue building in today, and increase in strength tonight and tomorrow.

PREV DISCUSSION
Issued at 313 AM HST Sat May 9 2026

Windward and mauka showers with some limited spillover to leeward areas are ongoing across the island chain. Satellite indicates low clouds over or near the higher terrain on each island, along with high clouds streaming in from the southwest.

A weak surface trough near Maui will slowly drift westward, reaching Kauai on Sunday. Trade winds will build in behind this trough from east to west through the weekend. Wind speeds will initially be light to moderate, but will become moderate to locally breezy into early next week. This trough will keep winds weak enough to allow for land/sea-breeze showers to occasionally develop over leeward areas, even as trade winds build in and bring their typical windward and mauka focused showers.

While that is occurring at the surface, the flow aloft will change significantly. We will transition from weak troughing to our north this weekend to the rapid development of a closed ridge to our northwest by Monday. This ridge will become elongated along an east-west axis and remain with us all next week. Its presence will keep a surface ridge in place, allowing the trades to blow at least through the end of next week, and likely longer. This means mainly windward and mauka showers will hang around. There will be occasional fluctuations in available moisture throughout this period, and these will result in periods of enhanced shower activity from time to time.

AVIATION
Moderate trades will steadily increase during the day today and become locally breezy in select areas. A weak trough passing through the state will increase showers, especially over windward and mountain areas with periods of MVFR conditions expected throughout the day today. A drier airmass will move in from the east this evening, which should bring a decrease of showers tonight. One exception is over Kauai, where showery conditions are expected to persist through tonight.

AIRMET Sierra remains in effect for mountain obscuration over Kauai, Oahu, Molokai and Maui due to the passing showers.

There may be the need for AIRMET Tango for low-level turbulence as trades gradually strengthen.

MARINE
A ridge will remain in place north of the islands with fresh trade winds today, strengthening Sunday and maintaining next week. A Small Craft Advisory (SCA) is posted for waters around Kauai and windward Oahu today through tonight. The typical windy waters around Maui County and Big Island will go into the SCA tonight. The SCA will likely be expanded to more areas by Sunday as winds strengthen.

A small northwest swell will maintain through the rest of the weekend, shifting out of the north to north northwest next week.
Small south swell will fade this weekend with a small, long period reinforcement Monday through Thursday. Surf along east facing shores will remain below normal this weekend, but will gradually increase next week as trade winds strengthen.

HFO WATCHES/WARNINGS/ADVISORIES
Small Craft Advisory until 6 AM HST Sunday for Kauai Channel- Kauai Leeward Waters-Kauai Northwest Waters-Kauai Windward Waters-Oahu Windward Waters.

Small Craft Advisory from 6 PM this evening to 6 AM HST Sunday for Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters-Maalaea Bay-Pailolo Channel.