Marine Weather and Tide Forecast for Ko Olina, HI

DISCUSSION
Visible satellite and radar imagery show isolated showers moving into windward areas on the weak trades, as well as a few showers developing over leeward interiors this afternoon due to sea breeze activity. Models continue to show that light to locally moderate easterly trade winds will persist into tomorrow morning before gradually strengthening into next week. Winds will likely remain light enough across the state to allow for the development of land breezes overnight, which should help to clear out leeward areas by morning. As the trades begin to strengthen tomorrow, sea breeze activity will be hindered some, but will likely still occur across some of the more sheltered leeward areas. This hybrid pattern of redeveloping trades and sea breezes will support isolated to scattered showers across windward and mauka areas tonight with additional isolated showers over island interiors tomorrow afternoon.

Another front will approach from the northwest through Sunday.
Models continue to show its tail end dissipating before it reaches the state, but batches of remnant moisture will move in on the strengthening trades early next week as high pressure strengthens to the north. These breezy to strong trades will persist through the week and into next weekend, focusing clouds and showers mainly over windward and mauka areas. Model guidance has been consistently showing an upper level shortwave trough move down the island chain early next week, then pinch off from the main trough to form a cutoff low south of the state before slowly retrograding westward through the week. The proximity of this feature may serve to help enhance windward showers, particularly over the southern end of the state, but no significant impacts are expected at this time.

AVIATION
Light trade winds will compete with local sea breezes to drive local weather patterns. During the day, afternoon sea breezes will encourage shower development over island interiors. After sunset, land breezes will develop and promote overnight clearing, especially along leeward coasts. Light trade winds will carry bands of low- topped clouds towards windward coasts both day and night.

The air mass over the state will remain dry and stable through the weekend. A strong inversion aloft between 07 kft and 09 kft will keep available moisture trapped in the lowest levels. Any shower activity will be light to moderate in intensity and limited in scope.

High pressure to our northeast will gradually strengthen. Moderate to locally breezy trade winds will return to the Islands early next week.

MARINE
High pressure building north of the state will bring strengthening trade winds to the region through Monday night. Light winds tonight will increase to moderate levels Sunday afternoon, with fresh to strong trades in place by Monday night. These fresh to strong trades will likely remain in place through the new week.
Small Craft Advisory (SCA) level winds are expected in the typical windier waters near Maui County and the Big Island Monday, with additional waters impacted Tuesday based on the wind criteria. From Wednesday onwards, additional areas may be placed under a SCA due to increasing seas.

The current northwest (330 degree) swell has brought surf heights near High Surf Advisory (HSA) levels along exposed north and west facing shores of the smaller islands. Surf is expected to fall below advisory levels this evening, with the swell continuing to decline through Sunday. As such the HSA remains in effect until 6pm today. Another northwest (330 degree) swell is expected to arrive late Sunday night, bringing another round of advisory level surf to the smaller islands by Monday afternoon, and then declining Tuesday night. Surf will once again be boosted early Thursday with yet another northwest swell, which could briefly bring surf advisory levels. A small south swell will continue through Sunday, before diminishing early next week. Increasing trade winds will bring an increase in choppy trade wind swell to the east facing shores this week.

FIRE WEATHER
Critical fire weather conditions are not anticipated over the next several days. For this weekend, winds will be too light and relative humidity too high to be of any concern. For next week, even though trades will strengthen to become breezy to strong, relative humidity will remain sufficiently high to continue to preclude critical fire weather concerns.

HFO WATCHES/WARNINGS/ADVISORIES
High Surf Advisory until 6 PM HST this evening for Niihau-Kauai Leeward-Waianae Coast-Oahu North Shore-Maui Windward West-Kauai North-Molokai Windward-Molokai North-Molokai West-Windward Haleakala.