Light to moderate trade winds will prevail for the next few days, followed by increasing trade wind speeds this weekend. Meanwhile, an upper disturbance just to the northwest will enhance showers over the western end of the state through Thursday. The focus for increased showers will shift to the eastern end of the state this weekend as an area of tropical moisture passes by.
Water vapor imagery shows an upper low west of the main Hawaiian Islands this afternoon. This feature is generating instability and wind shear across the western end of the state that will last until Thursday. The upper low is forecast to lift away to the north on Friday, returning more stable conditions to the area.
Meanwhile, trade winds will remain at only light to moderate speeds for the next couple of days as the remnants of former Tropical Cyclone Genevieve have cut off the high pressure to our north, interrupting the trade wind flow. The weaker trades will likely result in localized sea breezes each afternoon, bringing increased cloud buildups and a few showers each afternoon. Showers will be more prominent across Kauai and Oahu due to more available moisture and instability. By the weekend, trade winds will increase back to locally breezy levels.
The forecast becomes more interesting again this weekend as model guidance continues to suggest that a plume of moisture will either move over or very near the eastern end of the state late Saturday into Sunday. Despite most guidance keeping the bulk of the moisture just south of the state, it is likely that at least some of the enhanced tropical moisture will become embedded within the trade wind flow, increasing showers for Maui and the Big Island.
A weak high pressure ridge far north of the state will maintain gentle to moderate trade winds through Thursday. Overall, a fairly dry afternoon and evening is expected, but a slight increase of showers is expected late tonight into Thursday morning, mainly over windward areas. Some of these showers could produce brief MVFR ceilings over select areas.
No AIRMETs are in effect. AIRMET Sierra may be needed across select windward areas late tonight into Thursday morning depending on shower coverage.
Moderate trades persist as surface troughing to the NE maintains a rather weak pressure gradient over the state. Dissipation of the trough to the NE combined with renewed trough development S of the islands will favor breezy trades by week's end.
Existing small S swell will fade tonight and will be quickly replaced by a similarly sized medium period S swell during Thursday. Small, medium period energy remains prevalent heading into the weekend. A larger, medium to long period S swell arrives early next week and likely peaks shy of the High Surf Advisory threshold by the middle of next week. Long period forerunners are expected to arrive as early as Friday evening or Friday night.
None.
