Issued: Dec 18, 2014 2:30 PM HST
Based on data through 2:00 pm Dec 18 2014 HST
Regional satellite imagery shows varying amounts of low clouds, including showery cumulus /cu/ and stable stratocumulus /sc/, moving over the islands from the east. Showery cu are in greater concentration over Kauai and Oahu and adjacent waters, where they are broken to overcast, with scattered to locally broken low clouds over windward waters east of Maui and the Big Island. In addition, relatively small patches of broken to overcast high clouds have recently developed near Kauai and Oahu, associated with a weak trough aloft moving southeast over the area.
Mostly cloudy skies prevail over Kauai and Oahu as showery cu move ashore over the windward sides, and spread leeward with the fairly strong trade winds, which are carrying low clouds toward the west at speeds near 27 mph. In Maui county, broken to overcast sc and cu are banked along the lower portions of the windward slopes, with scattered low clouds over leeward areas. One exception is southwest Maui near Ulupalakua, where broken to overcast sc line the lower leeward slopes of Haleakala. The central valley and the summit of Haleakala are under mostly sunny skies. On the Big Island, interior and upslope portions are under sunny skies, with scattered to locally broken sc and cu lining the slopes above Hilo town. Broken to overcast sc are seen over the northeast and northwest sides of the island, from Honokaa to upolu to near Waikoloa Village resort.
The low cloud field near the islands continues to be dominated by showery cu elements, with a mix of stable sc and showery cu prevailing elsewhere across the tropical central north Pacific. Water vapor imagery shows the islands well south of the polar jet, which is located north of the area north of 34°N, with a relatively stagnant flow aloft over the main Hawaiian islands. A weak northeast to southwest oriented trough aloft is located near Kauai, and is moving toward the southeast. This is the feature that is responsible for the patchy high clouds near Kauai and Oahu. A large high aloft is centered west of the date line near 20°N 170°E, and an associated ridge aloft extends northeastward over Midway atoll and the northwestern Hawaiian islands.