Breezy trade winds will persist into Thursday, with showers favoring windward and mauka areas. Friday into the weekend, trades will ease slightly and a passing upper-level disturbance, along with increasing moisture, may bring an uptick in trade wind shower activity, with pockets of heavy rain possible. Then a more stable, breezy trade wind pattern should redevelop by midweek next week.
Broad high pressure to the far north of the state (centered around 40 N) will maintain breezy trade winds across the region into Thursday, delivering clouds and isolated to scattered showers to windward and mauka areas, particularly during the overnight to early morning hours.
During this time, a weakness will develop in the ridge aloft and a mid- to upper-level low will break away from the base of a longwave trough and move directly over the main Hawaiian Islands by Friday evening. This upper level disturbance will induce a broad surface trough over the region, weakening the local pressure gradient and allowing the trade winds to ease and veer slightly. Cooler temperatures aloft and the potential weakening of the low- level inversion will help to create a more unstable environment over the state, likely enhancing trade wind showers. In addition, deep tropical moisture will move up from the south, with models showing precipitable water values climbing into the 1.5 to almost 2 inch range over the eastern end of the state. This setup will likely bring enhanced showers to the western end of the state beginning on Friday where the greatest instability will be, then transition over the eastern end by Sunday into Monday, where the deepest moisture will be. The main limiting factor to a more organized enhanced shower setup is the lack of any strong lifting mechanism at the surface. As such, the most likely locations to experience heavy rain are the windward and mauka areas that are impacted by orographic lift in a trade wind pattern, though the hi-res guidance is just now reaching Friday afternoon where they also highlight interior and leeward Oahu as the upper-level low moves overhead and the background winds become light enough to support sea breeze development. In addition to the the potential for pockets of heavy rain this weekend, dew points are expected to rise into the lower 70s, leaving this weekend feeling muggier with lighter winds.
Beyond Monday, differences between the global models become more apparent, but for now, expecting a more stable, breezy trade wind pattern to redevelop by midweek next week.
A breezy trade wind pattern will continue through Thursday due to a high pressure system far north of the islands. Showers will continue to be carried in on the trade wind flow, at times bringing some MVFR conditions mainly to windward and mauka areas. Otherwise VFR conditions are expected to prevail.
AIRMET Tango remains in effect for mechanical turbulence to the lee of the mountains due to the breezy trade winds. Expect this to remain in place at least through Thursday.
High pressure established north of the islands maintains locally strong trades until an upper disturbance causes winds to weaken by this weekend. Late morning ASCAT indicated Small Craft Advisory (SCA) conditions continuing within the windier waters of Maui County and the Big Island. The SCA therefore remains in effect for those zones.
Small, short period NW swell fades today and will be replaced by a small to moderate, long period NW swell that will peak on Thursday bringing small to moderate surf to favored exposures. Small, medium to long period S swell maintains small surf along S shores. Meanwhile, locally strong trades maintain choppy short period conditions along E shores.
Tides peak around 2.5 ft MLLW this weekend. Combined with ongoing trades and a modest boost in S swell, water levels will peak around 3.0 ft late this weekend into early next week. Minor overwash of low lying coastal areas will be possible at high tide during this time.
Small Craft Advisory until 6 PM HST Thursday for Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters- Maalaea Bay-Pailolo Channel.
