Issued: Nov 22, 2009 8:00 PM HST
Synopsis
High pressure northeast of the state will shift further east allowing trade winds to drop to moderate levels early this week. Trade winds will increase again mid week. Showers will remain focused on windward and mountain terrain over the next several days.
Discussion
Not expecting any significant changes to the benign trade wind pattern from the day shift. Water vapor imagery depicts a southeastward moving shear axis over the islands. This is contributing to some minor instability well above 15 kft, which is well out of reach of the locally limited moisture in the well capped boundary layer. Blended total precipitable water imagery reveals generally dry air upstream with Hawaii, which is sitting just outside the northern fringe of the rich tropical ITCZ moisture to the south. Some of this moisture may graze the state late Tuesday through Thursday. However, with stable thermodynamic profiles expected to persist, this will limit the vertical development of any showers keeping them windward terrain focused mid week.
Trades will weaken slightly during the first half of the week as high pressure to our northeast is displaced further east by an amplifying deep layered trough to the north. Mid latitude flow will remain progressive ushering in height rises and surface high pressure to our north again by mid week allowing trade winds to strengthen once again. This will also limit the equatorward reach of any attendant frontal activity. Regardless of fluctuating batches of moisture passing in the trades the weather will remain pleasant through the forecast period.
Previous discussion
' issued 400 pm HST saturday' precipitation through the day has been sparse, mostly confined to the windward Big Island. Satellite imagery shows some shower clouds upwind, which is to the east northeast of the main Hawaiian islands, that may come ashore later tonight. The showers would be less significant than last night. Afternoon balloon soundings are stable and relatively dry.
Marine
The current high surf advisory for north and west Kauai and Niihau, as well as north shores of Oahu Molokai and Maui runs through Monday night. It is possible the advisory may be extended through Tuesday.
Larger surf is likely late Tuesday night into Wednesday. Surf along north facing shores could reach or exceed the 25 foot warning level mark from the northwest. This will drop slowly into the second half of the work week, possibly followed by another advisory level swell over the weekend.
South facing shores will see continued waist to shoulder high southern hemi swell Monday. A decreasing trend will begin Monday night through mid week. Modest southeast swell will appear during the second half of the week possibly hitting the chest high mark along the better exposed reefs' beaches.
Aviation
Expect vfr conditions to prevail for the terminals tonight. Trade winds will focus -shra over windward' mt terrain overnight with high end transient mvfr cigs' vis. Phny will could see the usual intermittent mvfr cigs tomorrow afternoon due the to the field elevation. Otherwise, no widespread flight restrictions are expected through the near term.
Watches/Warnings/Advisories
High surf advisory until 6 am HST Tuesday for niihau-kauai windward-kauai leeward-oahu north shore-oahu koolau-molokai-maui windward west-windward Haleakala.
MARINE...DEJESUS/HOAG
PREVIOUS...HOAG