Breezy trades deliver an increased coverage of showers windward and tonight through the weekend.
Stagnant upper air pattern between roughly 20N and 30N persists as the islands remain under the influence of a narrow upper ridge axis flanked on either side by cutoff lows. Expectedly, governing high pressure changes very little during the forecast period leaving the islands in a rather typical breezy trade wind pattern. A transition to a wetter trade wind pattern commences tonight as visible imagery shows a band of shower-bearing cu advancing WNW toward Maui County this afternoon. This band of showers is oriented perpendicular to the island chain and as such poses the potential to bring a few inches of rain to select windward locales as training showers become established. Given observed WNW motion and latest guidance, suspect Kauai may be the most likely to experience several hours of moderate shower activity potentially lingering into Thursday.
The lead edge of a tropical airmass characterized by PWATs around 1.75" is evident on visible imagery as a SW-NE oriented band of clouds centered on 20N/150W east of the Big Island. This airmass will bring dewpoints into the low 70s and maintain the ongoing period of wetter trades into the weekend. Continued breezy trades will help take the edge off of mugginess as higher humidity builds. General signal from the medium range guidance is for increased shower coverage to continue into early next week, predominantly overnight and during the early morning hours.
Breezy to locally strong ENE trade winds will continue tonight through the next few days. Periodic pockets of enhanced low level moisture will boost showers mainly along windward and mountain areas with occasional leeward spillover. Showers will also be more active during the night time and early morning hours. Overall VFR conditions are expected with passing MVFR conditions in the showers.
AIRMET Tango remains in effect for moderate low level turbulence over and downwind of terrain for all islands. This AIRMET will likely continue through the next several days.
AIRMET Sierra is also possible during the overnight hours for windward and mountain areas if showers increase.
Strong high pressure centered north of the state continues to drive fresh to strong trade winds across all coastal waters. The ASCAT from earlier today only clipped the eastern end of the state, but confirmed Small Craft Advisory (SCA) level winds in the Alenuihaha Channel and across waters south of the Big Island. Hi-resolution guidance keeps Small Craft Advisory (SCA) winds in many of the coastal water zones though tonight, so will keep the current SCA through then. Very little change is expected to the strength of the high or the pressure gradient across the islands, so will continue to remain around the advisory threshold for most waters over the coming days. The SCA will likely be extended beyond tonight for the typical windy zones around the Big Island and Maui County at a minimum, but additional zones might need to be included.
A small to moderate, medium-period south southwest (190-200 degrees) swell continues to generate moderate surf below advisory criteria along south facing shores this afternoon. This swell energy will gradually lower through the remainder of the week. Expect small surf for south facing shores leading into this weekend, with mainly background energy. A small to moderate, long-period southwest swell (220 degrees) is expected to fill in Saturday into early next week, but due to its Tasman source, could be more inconsistent than the current swell.
Surf along east facing shores will remain rough and choppy through the week as fresh to strong trades hold. A series of small, moderate- to long-period west (270 to 280 degrees) swells are expected to arrive this weekend and linger into early next week, sourced from Typhoon Bavi in the far western Pacific. No significant swells are expected out of the north or northwest.
Looking ahead, higher than normal high tides will be possible beginning during the latter half of this weekend. Interests immediately along the coasts in low-lying or vulnerable areas should continue to monitor forecasts for possible coastal flooding due to the King Tides from Sunday through the first half of next week.
Small Craft Advisory until 6 AM HST Thursday for all Hawaiian waters-
