Latest observations show that a light easterly flow prevails in the low levels, with winds light enough to allow localized land breezes. The winds are being supported by a distant high that is relatively weak, with weak troughs between the high and the islands contributing to a loose pressure gradient, as is the nearly stationary remnant circulation of Marie, about 1300 miles NE of the islands. Although skies immediately upstream of the islands from Kauai to Molokai contain only isolated showers, an area of showery low clouds lies over windward waters out to 200 miles E of Maui and the Big Island, moving W at 10 to 15 mph.
Today, abundant sunshine is expected over leeward areas, while windward areas will be partly cloudy with a few brief showers. Showers/clouds are expected to be a little more active through tonight over windward Maui and Big Island as the aforementioned area of moisture moves W. After this modest moisture source passes, limited moisture is expected through Thursday. Increased moisture loosely associated with the remnant of Marie passing far NE of the islands may increase windward showers from Thursday night through Saturday. A mid-level ridge near the islands will ensure that the atmosphere remains strongly capped at about 8 to 10 kft.
Trade winds are expected to be slightly stronger today as compared to the last 2 days, as the troughs NW of the islands weaken and the surface ridge to the N strengthens somewhat. The overall synoptic pattern does not support a strong trade flow this week however, but rather a light to moderate flow. Therefore, one of the biggest forecast questions over the next couple of days involves the strength of the trade winds, and whether or not afternoon sea breezes will become sufficiently strong/widespread to drive cloud and shower development over leeward and interior areas. Although a slight increase in leeward sky cover is in the forecast grids for the smaller islands today, no significant pops are indicated. Some uncertainty as to how this will verify. The leeward Big Island is the exception, where leeward clouds and showers are expected every afternoon and evening through the forecast period.