050 
fxhw60 phfo 061955 
afdhfo 


Area forecast discussion 
National Weather Service Honolulu HI 
1000 am HST Sat Sep 6 2008 


Synopsis... 
light to moderate trade winds will diminish from Monday Onward. The 
stable atmosphere over the islands will limit windward rainfall... 
but Lee areas may experience increased clouds and a few showers. 


&& 


Discussion... 
satellite and nexrad output show nothing unusual is in store in the 
near future. I... is just the usual random distribution of 
scattered trade wind clouds and showers within 300 miles northeast 
of the state. 


Models keep the North Pacific high stuck off the Pacific northwest 
coast with a ridge running southwestward to north and northwest of 
the islands. The pressure gradient south of the ridge is sufficient 
to put slightly lighter than normal trade winds across the state. 
The ridge slants southward with height...and is directly overhead 
about Half Way up through the atmosphere pressurewise. Subsidence 
with both the surface ridge to the north and the middle-level ridge 
overhead will keep the islands dry for the most part into Monday. 


Models also agree that the 500 mb ridge will lift to the north 
allowing a 500 mb low to slide westward to just northeast of the 
islands along 150w on Monday. They then say that the low will lift 
out to the northeast on Wednesday. According to guidance...the 
departure of the ridge and the approach of the low will have little 
or no effect on island precipitation. What is more likely to happen 
is that the upper low will erode the surface ridge resulting in even 
lighter trade winds from Monday Onward. See no reason to disagree 
with this game plan. 


The only question to keep in mind is whether daytime sea breezes 
will set up while the trades are light. If the breezes do form... 
there may be afternoon showers over normally dry leeward sections. 
The forecast for now calls for trade wind showers favoring the 
night and morning hours rather than sea breeze showers favoring 
afternoon and evening hours. We may of course need to adjust the 
forecast should it become more apparent that a weak convective 
pattern will override the light trades. 


&& 


Marine... 
the large south swell will decline slowly. A high surf advisory for 
south-facing...and a marine weather statement for waves breaking 
across Harbor entrances remains in effect. A new south southeast 
swell will arrive late this weekend...producing surf approaching the 
advisory level on Monday and Tuesday. 


&& 


Hfo watches/warnings/advisories... 
high surf advisory until 6 PM HST Sunday for south facing shores. 


&& 


$$ 


Craig