Issued: Jul 26, 2014 2:30 AM HST
Based on data through 2:00 am Jul 26 2014 HST
The pressure gradient south of a surface ridge located more than 1100 miles north of Honolulu was maintaining moderate trade winds across the main Hawaiian islands early this morning. The low-level trade wind flow was carrying scattered to locally broken low clouds with embedded isolated showers across the windward Hawaiian waters. There were also patches of low clouds and a few showers over the ocean leeward of some of the islands.
The individual low cloud elements over the windward coastal waters were generally moving westward at 15 to 20 mph. The highest tops of the low clouds in the vicinity of the main Hawaiian islands were estimated to be 7 to 8 thousand feet. Upstream from the islands, the leading edge of a large area of mainly broken low clouds with embedded scattered showers was about 70 miles east of Hilo. This leading edge has advanced westward at almost 20 mph during the past 6 hours.
As of 200 am HST Saturday, there were scattered to broken low clouds across parts of Kauai. Broken low clouds were along the windward shoreline and Koolau range of Oahu. There were mainly scattered low clouds elsewhere on Oahu. Skies appeared to be mostly clear on Molokai, while a few low clouds were detected above Lanai. On Maui, broken low clouds were affecting parts of the windward coastal areas, the lower windward slopes of mount Haleakala and the western mountains. Scattered to broken low clouds covered portions of the lower elevations of the windward Big Island.
According to loops of water vapor imagery, the axis of a narrow upper level trough extended from near 30°N 160°W to 19°N 172°W, or about 545 miles west northwest of Lihue. This upper level feature has propagated toward the east southeast at about 10 miles per hour during the past 6 hours. A subtropical jet stream along the southeastern flank of this trough aloft extended from near 20°N 167°W to 25°N 158°W. Southwesterly winds of 55 to 75 miles per hour within the core of the jet stream were carrying a few wisps of cirrus clouds rapidly toward the northeast just to the west of Kauai. Elsewhere, an upper level ridge just east of the Big Island extended northward from an upper level anticyclone centered near 13°N 156°W. The close proximity of this upper level ridge was contributing to the stable conditions across the aloha state early this morning.
In the deep tropics far south of the main Hawaiian islands, the Central Pacific Hurricane Center has been following an elongated surface trough located about 720 miles south southeast of South Point on the Big Island, which has been moving westward at about 10 mph. However, there has been a dramatic decrease in the coverage of showers and thunderstorms associated with this system since early Friday evening. The surface trough extended further east from this disturbance through 10°N 149°W to 12°N 140°W. Isolated moderate thunderstorms were within 200 miles of this section of the trough. The highest tops of these cumulonimbus clouds were estimated to be 53 thousand feet.
Elsewhere, the National Hurricane Center /nhc/ in Miami, Florida is issuing advisories on tropical storm Genevieve, located about 1350 miles east southeast of Hilo. Based on the latest forecast, Genevieve is expected to cross longitude 140°W into the north central Pacific ocean late tonight or early Sunday morning. For additional information on Genevieve, see public advisories issued by NHC under WMO header wtpz32 KNHC and under AWIPS header MIATCPEP2.