153 
fxhw60 phfo 230556 
afdhfo 


Area forecast discussion 
National Weather Service Honolulu HI 
800 PM HST sun Nov 22 2009 


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 middle 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 inter-tropical convergence zone 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 middle 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. Middle latitude flow will 
remain progressive ushering in height rises and surface high 
pressure to our north again by middle 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 middle 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/Montana terrain overnight with high 
end transient MVFR cigs/vis. Phny will could see the usual 
intermittent MVFR ceilings tomorrow afternoon due the to the field 
elevation. Otherwise...no widespread flight restrictions are 
expected through the near term. 


&& 


Hfo 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. 


&& 


$$ 


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