Issued: May 24, 2013 8:30 AM HST
Based on data through 8:00 am May 24 2013 HST
Water vapor loop, showing features mainly above about 24000 feet, depicts an upper trough oriented northeast to southwest across much of the central north Pacific. With an axis extending through 31°N 140°W, 26°N 160°W and 14°N 180°W, this feature just north of the main Hawaiian islands has lingered across the area for at least the past 24 hours. The southern flank of this upper trough is marked by a ragged 200 mile wide band of broken high clouds generally south of a line from 21°N 160°W to 17°N 170°W to 12°N 180°W. Broken to overcast layered clouds north of a line from 40°N 140°W to 37°N 160°W to 30°N 180°W simultaneously mark the northern flank of the upper trough and the southern edge of a broad frontal cloud band.
The main surface feature across the central north Pacific, at least south of 40°N, is a broad anticyclonic circulation centered near 37°N 144°W, far northeast of the main Hawaiian islands. This circulation, actually a subtropical high, has a ridge which extends through 30°N 160°W and 22°N 180°W, almost directly beneath the upper trough axis. Low level flow is generally east to west south of the ridge axis, including across the main Hawaiian islands. Isolated cumulonimbus, CB, are noted west of the islands mainly from 19°N to 23°N between 164°W and 170°W.
Cloud cover across the main Hawaiian islands follows a rather typical trade wind weather distribution, with low clouds favoring windward areas of most of the islands. Kauai has scattered to broken low clouds across a small section of windward slopes north of Lihue. An area of middle and high clouds is also moving southward across Kauai. Oahu has broken low clouds along the Koolau summits, but the rest of that island appears to be clear. Broken low clouds also cover the eastern tip of Molokai, windward slopes of Lanai and windward Haleakala slopes on Maui. The west Maui mountains also have broken low clouds. All windward Big Island slopes have overcast low clouds. This cover wraps southwestward around Cape Kumukahi across Kau district as well. The Big Island plume terminates along the Kona coastline between Milolii and Captain Cook. Satellite loop shows low clouds are moving west across local waters at 15 to 20 mph.