Issued: Nov 23, 2009 2:30 PM HST
Based on data through 2:00 pm Nov 23 2009 HST
Water vapor imagery continues to show a wedge of very dry air in the mid and upper-levels of the island atmosphere, due to large scale sinking motion over the islands associated with a sprawling anticyclone aloft centered west of the islands. A relative minima in trade wind cumulus ' cu' and stratocumulus ' sc' is noted in the low levels beneath this area of dry air aloft, especially now that an area of scattered to broken low clouds over windward waters of the islands has decreased.
Large scale view of the tropical central north Pacific shows that the main Hawaiian islands are in area of relatively few clouds, with low cloud motions outlining the axis of a low-level ridge of high pressure that is located not too far north of Kauai. This ridge extends southwest from a high centered well northeast of the islands, and appears to have been shunted southward, and the high eastward, due to a southeast-moving frontal cloud band about 700 miles northwest of the islands, and it' s powerful eastward-moving parent low well north of the islands.
An area of broken cu and sc that was over windward waters of the islands this morning has decreased in coverage, with only a small area of scattered to broken cu located over waters north of Oahu and east of Kauai. Aside from a narrow plume cloud extending westward from Niihau, skies over waters adjacent to the islands are nearly clear this afternoon. An increase in low cloud cover is seen east of 155°W, but these scattered small fair weather cu appear to contain little, if any, in the way of precipitation, with this meager low cloud cover extending east of 150°W to near 145°W.
On Kauai, scattered cu are over the windward slopes, while coastal and leeward areas are mostly sunny. On Oahu, the Koolau range has broken cu coverage that is typical for trade wind flow, with scattered to broken cu over the central plateau, and isolated cu over leeward areas. The islands of Maui county have a typical trade wind distribution of low clouds this afternoon, with broken cu along the windward slopes of Molokai and Maui, and broken cu over the southwest slopes of Haleakala spreading westward over Kahoolawe and adjacent waters. The exception would be Lanai, where low clouds are fewer than normal, and skies are mostly sunny. The big island' s leeward coast and slopes are unusually sunny for the afternoon, with few to scattered sc over the slopes. Overcast sc are over the lower slopes of the Hamakua and Hilo districts, and over the lower slopes of the Kau district.
