Last Updated on Saturday, 20 September 2014 11:50
Issued: Sep 20, 2014 7:30 PM HST
Regional satellite imagery shows that while the main Hawaiian islands lie in an area of relatively few low clouds, skies over most island areas and adjacent waters are mostly cloudy. The clouds developed over the islands late this morning and during the afternoon, in response to sea breezes converging over the islands.
Isolated cold cloud tops have been noted over the islands over the course of the afternoon, representing areas of heavy showers. While most of the cloud tops over the islands and near shore waters are in the process of warming, representing a weakening trend to the showers, a couple of areas of cold cloud tops are still noted. The coldest cloud tops are currently noted over southeast Big Island slopes, where cloud top temperatures near -35 c correlate to cloud tops near 35 thousand feet. Infrared imagery shows cloud tops cooling over interior and southwest Oahu over the past hour or so, associated with developing showers that are seen by radar. Elsewhere, broken to locally overcast skies are noted over the islands and near shore waters.
Water vapor imagery shows a sharp trough aloft over the island chain, with the northeast to southwest oriented trough over Maui county, and is moving toward the southeast at 10 to 15 mph. With the trough aligned in this manner, winds aloft over Kauai and Oahu are from the northeast, while winds aloft over the Big Island are from the southwest. A ridge aloft is seen to the distant southeast of the main Hawaiian islands, and southwesterly winds aloft between the trough and the ridge are leading to upper level winds that are not conducive for the further development of a westward-moving tropical disturbance located about 400 miles south-southwest of Oahu. Scattered showers and thunderstorms, as well as layered mid and high level clouds, associated with this disturbance are located from 13°N to 19°N between 153°W and 160°W.
While the islands lie in an area of relatively few low clouds on the large scale, an east to west oriented cloud band is about 525 to 600 miles north of Oahu, sagging southward slowly. Another cluster of nearly stationary low clouds is about 300 to 400 miles north of Maui county.