Trade winds will return the next couple of days under typically partly cloudy conditions. Precipitation will primarily focus along upslope mauka and higher terrain with afternoon heating introducing isolated leeward showers. Higher chances for more frequent rain episodes will occur from Friday into early next week across better windward exposures.
A tranquil, dry morning across the islands under partially clear skies and light, variable breezes. Water vapor imagery is evidence that moisture levels are near to slightly below normal by seasonal standards. Weak troughing located a few hundred miles northeast of the state will likely provide just enough instability to go with low end moderate rain chances today and tonight. Early day warming under mainly clear skies will initiate thicker clouds and increase scattered showers over leeward Big Island's Kona region. Trades will return today but likely still be weak enough for localized sea breezes to develop and become the dominant flow pattern. Early day Sun on leeward slopes, with sea breezes drawing up higher moisture, will increase leeward isolated showers.
On the synoptic scale, Hawaii lies within a height weakness region between two surface high pressure systems, one far northwest of the islands and the other far northeast of the state. This has created a relaxed surface pressure gradient and maintained localized sea breezes during the day followed by nocturnal drainage or land breezes. The presence of a northeast surface trough, with approaching weak mid to upper level troughing from the northwest within a somewhat moistened environment, will ensure thickened mauka clouds and more frequent precipitation within higher elevations. Tomorrow will be another partly cloudy day with thicker clouds and more frequent showers being confined to windward upslope regions and higher terrain. While feeling a touch more humid due to the lack of moderate trades, thicker cloud cover should keep many locales in the mid to upper 70s for the majority of the afternoon. High pressure to the northwest will move across to the north the next couple of days. This will assist in tightening up the pressure gradient over the islands and strengthening trade winds. Trades will gradually make their return tomorrow and strengthen to more moderate magnitudes this weekend.
Overall troughing will lift northeast of the state going into the early part of next week. A general weak troughing pattern will hang over the state through Monday. Ribbons of higher moisture moving in on more established trades in a deeper boundary layer will promote the increased frequency of light to moderate precipitation, especially over traditionally more wet areas such as Kauai and Oahu's higher elevations, eastern Maui County and windward Big Island. More robust ridging is forecast to expand in from the west early next week. This will provide greater stability in tandem with a relatively drier atmosphere. Thus, overall statewide shower activity will be on the decline going into the middle of next week.
Light to moderate trades gradually build back across the area today, resulting in clouds and shower development along windward and mauka areas. MVFR conditions are possible in any shower activity. Otherwise, VFR conditions prevail.
No AIRMETS are in effect.
A weak trough residing northeast of the islands will keep trade winds light to locally moderate across all local waters today into Friday. By this weekend, a surface ridge building northwest of the state will bring a return of moderate to locally fresh trades. A Small Craft Advisory may be needed for the typical windy waters surrounding Maui and the Big Island by early next week late as the high expands eastward.
A moderate, long period, northwest swell is filling in across the local waters, as noted on the latest Hanalei buoy observations. This swell should peak later today and bring elevated surf along north and west facing beaches, just shy of advisory levels. Expect a gradual decline to swell and surf Friday into the weekend.
A small, long-period, south swell will continue to fill in today. This swell should provide a small bump in south shore surf through the end of the week.
Surf along east facing shores will remain below normal during the next several days due to the lack of strong trades over and upstream of the islands. East shore surf will gradually increase into the weekend as trades make a slow return.
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