Issued: Jul 06, 2015 8:00 PM HST
The tightening pressure gradient south of the southern end of a surface ridge has caused the low-level trade wind flow to gradually increase during the past 24 hours. This low-level flow has been transporting scattered cumulus clouds with embedded isolated showers toward the main Hawaiian island chain. The individual low cloud elements over the windward Hawaiian coastal waters were generally moving toward the south southwest at about 20 mph. The highest tops of the low clouds were estimated to be 8 thousand feet.
As of 700 pm HST, broken low clouds covered most of the northeastern half of Kauai, while scattered low clouds were elsewhere on that island. Broken to locally overcast low clouds were along the Koolau mountain range, with scattered to broken low clouds across most of the rest of Oahu. Scattered to broken low clouds covered most of the eastern tip of Molokai. Skies appeared to be mostly clear on Lanai and the remainder of Molokai. On Maui, broken low clouds were along the windward coast and lower windward slopes of mount Haleakala, as well as over parts of the western mountains. Broken to locally overcast low clouds covered portions of the southern and southwestern upslope and coastal areas of the Big Island, as well as most of the lower elevations of the windward Big Island.
According to loops of water vapor imagery, a nearly stationary mid-tropospheric low was centered near 22.5°N 151°W, or about 320 miles northeast of Hilo. A mid-tropospheric trough extended from this low to a point about 180 miles east southeast of South Point. As a result, mid-tropospheric winds across the main Hawaiian islands were from the north and north northeast at 10 to 20 mph.
There were a number of systems of interest in the deep tropics south southwest through southeast of the main Hawaiian islands. Of most interest to the islands over the next few days was a large area of low pressure located about 1350 miles east southeast of Hilo. Showers and thunderstorms associated with this system continued to gradually become better organized. However, satellite data suggested that the low does not have a well-defined low-level center at this time. Environmental conditions are expected to remain conducive for continued development, and a tropical cyclone will likely form during the next day or two as this system moves toward the west northwest at 15 to 20 mph.
Persistent showers and thunderstorms near a weak, nearly stationary surface low were located about 775 miles south southeast of Hilo. This system remains disorganized this evening, and environmental conditions do not appear to be favorable for significant development in this area during the next two days. Showers and thunderstorms associated with a broad area of low pressure located about 1100 miles south southwest of Honolulu have become slightly better organized this evening. Environmental conditions appear to be conducive for some slow development of this nearly stationary system through early Wednesday evening.