Light to moderate east-southeasterly winds will persist today, then take on an east northeasterly component by Sunday. Despite the slight variation in wind direction, the light to moderate background flow will bring a combination of mainly isolated windward and mauka showers along with sea breeze induced leeward and interior showers. Early to mid- next week, trade winds will strengthen to moderate to breezy levels, bringing a return to more consistent windward showers.
Mainly dry conditions prevailed overnight across the state with very little low cloud cover and isolated showers. Areas along the windward slopes saw most shower coverage, though only a few hundredths of an inch of accumulation were reported. A typical lower level moisture profile can be noted on the 12Z RAOB sounding at Hilo and Lihue with a capping boundary layer temperature inversion height of around 7,000 feet. Dry and stable air dominated in the mid and upper levels. Zooming out, a stationary front was analyzed to the northwest of the state and a 1029 mb surface high resided well to the northeast. These features should help maintain light to moderate east southeast flow today, backing to east northeast by Sunday. Despite the slight variation in wind direction, the light to moderate background flow will bring a combination of mainly isolated windward and mauka showers along with sea breeze induced leeward and interior showers. It may feel humid once again today with dewpoints hovering in the lower 70s. However, expect some relief for Sunday and beyond as we transition into a more traditional east northeast trade wind pattern and dewpoints gradually fall back into the mid to upper 60s.
Monday through Friday, the aforementioned frontal system northwest of the islands weakens into a trough, moves west, and is replaced by an large area of surface high pressure. Tightening local surface pressure gradients across the state will lead to moderate to locally breezy trade winds. In addition, both the GFS and ECMWF models deepen a longwave trough north of the islands, pinch off an upper low, and retrograde it to the west southwest. There still remains some variance between the global models on where this upper level low tracks, but as it nears the islands by midweek, it may enhance trade wind showers as batches of moisture roll through.
Stable weather conditions will continue through the weekend as strong subsidence aloft limits vertical cloud development over the islands. Light to moderate trade winds will persist as a diminishing stationary front far north of the islands keeps the high pressure ridge in a weakened state. Trade winds strengthen by Monday. No AIRMETs in effect.
Light to moderate trades will hold for the next couple of days as a weak surface ridge remains northeast of the area and a front passes to the north. Trade winds will begin to increase Monday and trend upward through next week as the front dissipates and the ridge strengthens north of island chain.
A small, medium-period south swell will continue to fade while a new long-period south swell builds through the day. Surf along south and west-facing shores should trend upward by the afternoon and peak overnight before diminishing on Sunday. Multiple other small, medium to long period south and southeast swells also arrive through the middle of next week, which will maintain surf heights near seasonal averages.
Tiny surf will prevail along north-facing shores through most of the coming week as limited short-period energy reaches the islands from the north and northwest. Trade winds remain lighter than normal through the weekend, keeping surf along east-facing shores below average. East shore surf will begin to trend up early next week as trade winds increase across and upstream of the region.
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