Issued: Sep 23, 2014 2:30 PM HST
Regional satellite imagery shows a moderate trade wind flow in place over the main Hawaiian islands. Few to scattered low clouds are approaching the islands from Oahu to the Big Island from the east, whereas low cloud coverage near and up to 200 miles north of Kauai is much greater, broken to locally overcast, with many of the low cloud elements having a showery appearance. The low clouds near Kauai are loosely organized in an east-northeast to west-southwest orientation, while the limited low clouds upstream of the other islands are randomly distributed.
On Kauai, scattered to locally broken low clouds are over the entire island, spreading to leeward areas after coming ashore along the windward side. These low clouds are moving over the island of Niihau, where skies are currently mostly cloudy. Low clouds have diminished rather significantly over Oahu since this morning, and sunny skies prevail island wide, with the only low clouds being few to scattered small cumulus over the summit of the Koolau range. Scattered to broken low clouds are along lower windward slopes of the islands in Maui county, and over southwest Maui near Ulupalakua, but the remainder of these islands are experiencing sunny skies. Abundant sunshine prevails over windward Big Island this afternoon, with broken to overcast low clouds along the lower leeward slopes, the Kau slopes, and the lower slopes of Hamakua. Some thin high clouds are moving slowly eastward over the Big Island and Maui, but are not having a significant impact on overall sky cover. Low clouds near the islands are moving toward the west at speeds between 20 and 25 mph.
A narrow band of east-west oriented broken low clouds is north of the area of showery clouds seen up to 200 miles north of Kauai, and is currently about 400 miles north of Oahu, moving south at 10 to 15 mph. The cloud band lies along a line from 29°N 140°W to 26°N 150°W to 27°N 160°W, and becomes increasingly diffuse to the west of that longitude. This band marks a front that ties into a powerful low far northeast of the islands. To the south of the islands, a westward-moving low level trough is passing just south of the Hawaiian offshore waters, and is producing isolated thunderstorms from 12°N to 16°N between 153°W and 157°W. Other randomly scattered thunderstorm clusters are located from 4°N to 11°N between 149°W and the date line.
Water vapor imagery shows a complex pattern aloft over the tropical and sub-tropical central north Pacific, with ridges aloft centered northwest of the islands near 30°N 165°W, and south of the islands near 10°N 160°W. Between the ridges, a nearly stationary east to west oriented trough aloft is along 20°N, and thus transects the Big Island. The thin high clouds noted earlier are moving within a west to east flow aloft just south of the trough axis.