A drier and less humid trade wind flow is filling in today. Limited showers will focus windward and mauka. A weak disturbance will lift out of the deep tropics early next week bringing a slight uptick in trades, increased humidity, and a better chance for showers.
A number of noteworthy features on infrared imagery this afternoon. To the northwest, a digging mid-level trough has triggered a convective flare-up as it feasts on the remnants of Lowell which itself is in the late stages of its baroclinic transformation. The lingering band of tropical moisture that has supplied the islands with humid conditions and spotty afternoon showers eased west of the islands last night, and dewpoints will accordingly fall more uniformly into the mid to upper 60s during the next 12-24 hours as moderate trades advect a drier airmass into the area. The delayed arrival of said airmass over Leeward Big Island means today's afternoon convection may yet provide a localized threat for nuisance flooding over downslope areas of the North & South Kona Districts similar to yesterday. However, satellite appearance of clouds in this area look stable and radar returns at press time are basically nil.
Near 05N/150W, or about 1000 miles SSE of Hilo, a disorganized area of showers and thunderstorms persists. NHC offers a 20% chance of tropical development with this activity as it lifts toward the islands early next week. Regardless of the low probability of development, enhanced moisture and a modest boost in trade winds will accompany this feature as it lifts out of the deep tropics. GFS offerings of very humid conditions characterized by mid-70s dewpoints during the middle of next week look appropriate and will provide rich low-level moisture in support of enhanced trade wind shower coverage.
Eyes remain fixed on Tropical Storm Norbert, 2000 miles ESE of Hilo, as it slowly advances westward at 14 mph. Any potential arrival in the vicinity of the Hawaiian Islands is at least 10 days away. Forecast uncertainty is characteristically high at that lead time and it will be several days before confidence in impacts, or lack thereof, improves.
Moderate trades will prevail through Saturday and continue to usher in isolated to scattered light showers to windward and mountain areas. Winds may be light enough to see isolated sea breezes in the most wind-protected leeward areas. The greatest coverage of low clouds and showers remains concentrated around the Big Island this afternoon, where tempo MVFR conditions are expected. Otherwise, besides in any brief passing showers, VFR conditions will prevail across the remaining TAF sites.
AIRMET Sierra remains in effect for tempo mountain obscuration on the Big Island through this evening and may need to be extended as moisture lingers across that region.
Moderate to locally fresh northeast to east trade winds will continue through the forecast period. A tropical disturbance moving in from the trade winds may bring an increase of showers to the coastal waters by next week Tuesday into Wednesday.
Surf along south facing shores will gradually decline through the weekend as the small medium to long period energy slowly fades. Currently a low in the south Pacific near Australia and New Zealand will bring the potential for a moderate long period swell for Hawaii late next week.
East facing shores will also remain at small to moderate through the forecast period due to the fresh to locally strong trade winds. Flat to tiny surf along north facing shores is expected through the forecast period.
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