Issued: Apr 24, 2014 2:30 AM HST
A brisk trade wind flow continues over the Hawaiian islands this morning, with varying amounts of low clouds tracking toward the islands from the east-northeast. Low cloud coverage upwind of the islands has increased somewhat since Wednesday evening, with scattered to broken clumps of showery cumulus /cu/ randomly distributed. Cloud top temperatures of the incoming cu are slightly cooler than they were 6 to 8 hours ago, indicating that the incoming clouds are reaching a slightly higher height, with cloud top temperatures near 7 degrees celsius equating to cloud tops near 11 thousand feet. While the bulk of the incoming clouds and showers are stacking up along windward coasts and slopes, the strong trades are briefly pushing these scattered to broken low clouds over leeward areas of the smaller islands. Low clouds and showers near the islands continue moving toward the west-southwest at 25 to 30 mph.
The leeward, or western, portions of the islands from Kauai to Maui generally feature partly cloudy skies, as periods of mostly clear skies are interrupted by scattered to broken cu spreading westward from the mountains. Windward portions of Kauai and Oahu have broken showery cu moving ashore, with few to scattered low clouds noted over windward waters east of Maui and the Big Island, thus slightly wetter and cloudier conditions are over Kauai and Oahu. While randomly distributed patches of low clouds prevail upstream of the islands for several hundred miles, and lack significant organization, the increased moisture over Kauai and Oahu is is associated with the southern fringe of a 500 to 700 mile long, 75 to 100 mile wide, east to west oriented diffuse band of broken cu. This band extends from waters just northwest of Kauai to several hundred miles northeast of Oahu. Portions of the poorly organized band to the northeast of the islands have sagged southward over the past several hours, and some of this moisture now seems poised to move over the islands at some point as it is now directly upstream of at least some of the islands.
Patches of scattered, and diminishing, high-level cirrus clouds are noted about 400 to 1200 miles northeast of the islands, and water vapor imagery shows these clouds are associated with a northeast to southwest oriented trough aloft, and a dissipating embedded low aloft, that is about 300 miles northeast of the islands. The trough aloft has an axis that passes north of Kauai, along a line from 30°N 150°W to 25°N 160°W to 18°N 180°, with a westerly flow aloft prevailing over the islands.