Light south to southeasterly flow will be with us into Friday, with overnight land breezes and daytime sea breezes. A lingering area of increased moisture will support scattered to numerous showers near the western end of the state for the next couple of days. Light to moderate trades return late Friday as surface high pressure northeast of the state becomes re-established.
A surface low north of the state will weaken through Friday, allowing surface high pressure well off to the northeast to become our dominant wind feature by Saturday. This will bring a return of light to moderate easterly trade winds, and limit the influence of sea and land breezes. However, until that time, today and tomorrow will still have a strong component of these breezes. This will once again bring an above-average amount of leeward showers to the state. The best chance for showers will be over Kauai, where a lingering but decaying boundary holds increased moisture. Radar has been active this morning, with lightning observed to the northeast of the Kauai coastal waters. Additional showers were observed over the southeast and northwest coasts of the Big Island.
Models have come into better agreement on the evolution of an upper level trough forecast to form nearby in the early to middle part of next week, with the trough expected to form just north of, and then drift just west of, the state. The surface reflection of this feature will increase the pressure gradient (low pressure nearby to contrast with the high far off to our northeast), and thereby increase east to southeast flow Tuesday and Wednesday. This is not a true trade wind due to its direction, but the increase in speed will result in a different pattern compared to what we are experiencing this week. The exact details of these differences will become clearer as we get closer in time.
Weak southeast winds will continue through tonight, resulting in sea and land breezes across the state. Expect more showers near PHLI than other TAF sites due to a decaying but still relevant moist axis drifting north across Kauai today. Most sites will see VFR conditions, but occasional MVFR and isolated IFR in showers is to be expected. No AIRMETS in effect, but mountain obscuration my redevelop over Kauai later today.
A surface trough near Kauai and Oahu will continue to drift northwest through the end of the week. Light to gentle southeast to south flow will also give way to localized land and sea breezes over nearshore waters. Gentle to locally fresh easterly trade winds will build in from the east through the day on Friday and hold through the weekend. Early next week, a potential surface trough develops north of the waters and may disrupt the trade winds for another round of light to gentle southeast winds.
A mix of a small, medium period northwest swell and a small, short period north northeast swell will maintain small surf for north facing shores through Saturday. Another small medium period northwest swell will fill in late Saturday followed by a moderate medium to long period northwest swell that is expected to fill in Sunday and peak on Monday near High Surf Advisory criteria. Recent model guidance has exhibited a low bias, compared with observed nearshore buoy readings running higher than forecast guidance. As a result, surf heights may come in larger then currently indicated by the model output.
Surf along south facing shores will remain small through the weekend with a series of small medium to long period south and southwest swells. East facing shores will remain tiny to small through Friday except for select shorelines exposed to the current small north northeast swell. A slight uptick is expected this weekend as easterly trade winds return. In addition, a small, medium to long period easterly swell from Tropical Cyclone Priscilla in the East Pacific is forecast to arrive late Saturday into Sunday.
Peak high tides associated with the lunar cycle will lead to minor coastal flooding along shorelines and low lying coastal areas through early next week. Coastal flooding will coincide with the daily peak tide each morning. A Coastal Flood Statement remains in effect for all coastal areas through Friday, but will likely need to be extended into early next week.
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