193 
fxhw60 phfo 231331 
afdhfo 


Area forecast discussion 
National Weather Service Honolulu HI 
330 am HST Monday Nov 23 2009 


Synopsis... 
high pressure northeast of the state will shift further east 
allowing trade winds to drop to moderate levels to start the week. 
Trades will increase again middle week. Showers will remain focused on 
windward and mountain terrain over the next several days. 


&& 


Discussion... 
still no significant changes to the forecast to wrap up the night 
shift. Shower activity will remain windward focused Monday with only 
light accumulations. Kept windward areas at pop 30-40 at the most 
tomorrow. Looking upstream towards the east there is an axis of 
higher precipitable water/relative humidity that could bring slightly higher probability of precipitation to windward 
zones late Tuesday night through Thursday morning. Did introduce a 
slight pop increase with numerous showers during the nighttime hours 
Tuesday and Wednesday nights. Trades will be a hair lighter to get 
the work week started due to an amplifying trough to the north. They 
will pick up again middle week and hold through the remainder of the 
forecast period as high pressure reasserts itself north of the area. 


&& 


Previous discussion.../issued 800 PM HST Sunday night/ 
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. 


&& 


Marine... 
no changes were made to the high surf advisory. Surf will remain 
solid into Tuesday...but should drop below advisory levels by then. 
The surf along north facing beaches/reefs will begin to increase 
abruptly again Tuesday night potentially requiring a high surf 
warning for waves exceeding 25 feet on the face by Wednesday with a 
slow decrease to follow thereafter. It is not out of the question 
for advisory level surf to persist through the remainder of the week 
along north facing shores. 


South facing shores will see continued waist to shoulder high 
southern hemi swell today. 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. 


The surf forecast product will be updated later this afternoon at 
300 PM HST. 


&& 


Aviation... 
VFR conditions will be the call for the terminals today with 
generally dry trade winds continuing. Phny will could see the usual 
intermittent MVFR ceilings this afternoon due the to the field 
elevation. Otherwise...no widespread flight restrictions are 
expected through the near term with any MVFR conditions remaining 
confined to windward terrain. 


&& 


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. 


&& 


$$ 


Dejesus