A weakening high pressure ridge north of the Hawaiian Islands will keep trade wind speeds on the decreasing trend from Friday into Saturday, then ridge and wind speeds strengthen from Saturday afternoon through Sunday night. Brief passing showers are possibly over windward and mountain areas during this time period, mainly during the overnight to early morning hours. The next best chance for statewide rainfall may develop from Monday into Tuesday of next week, as the cloud remnants from an old cold front drift across the islands on the trade winds.
Drier conditions are settling in across the smaller islands in the wake of a dying front. Windward Big Island may still receive an increase in showers overnight as the frontal boundary continues pushing through the state. Winds will ease, becoming moderate to locally breezy tonight into tomorrow. Embedded trade wind showers are still possible over windward and mountain areas across the rest of the state through tomorrow, providing brief MVFR conditions to those areas. Otherwise VFR prevails.
AIRMET Tango is in effect for low level moderate turbulence downwind of terrain. AIRMET Sierra is in effect for mountain obscuration over windward areas of Big Island. Overnight clouds and showers could keep this AIRMET in effect until tomorrow morning.
Strong high pressure north of Hawaii will maintain fresh to strong winds across the marine areas through tonight. A late morning advanced scatterometer (ASCAT) pass showed Small Craft Advisory (SCA) winds prevailing over the region. Therefore, the SCA remains in effect for all waters through tonight, but will likely need to be extended for at least some zones on Friday. Seas are also in excess of 10 feet as a large northwest swell gradually declines. Though trade winds will diminish some on Friday and Saturday, high pressure restrengthening northeast of the islands may bring more widespread strong winds Sunday and Monday to all waters.
This afternoon, PacIOOS Buoy 51201 continues to show a declining northwest swell around 8 feet 15 seconds. Given this, and surf observations from around the state, the High Surf Advisory (HSA) remains in effect for north and west facing shores of Niihau, Kauai, Oahu, and Molokai, and north facing shores of Maui, and has been extended through tonight. This northwest swell will decline tonight, then fall below advisory criteria by early Friday. Surf will continue to decrease throughout the day on Friday, but will experience another small bump on Saturday with a new north- northwest swell, followed by a more significant north swell which could push surf back to advisory levels on Sunday.
Surf along east-facing shores will remain rough and choppy due to the strong trade winds through Friday. East-facing shores may decrease briefly as trades begin to ease early this weekend, but will increase again Sunday into early next week as trades increase again. South shore surf will tiny to small for the next few days.
Small Craft Advisory until 6 AM HST Friday for all Hawaiian coastal waters and channels.
