154 
fxhw60 phfo 080654 
afdhfo 


Area forecast discussion 
National Weather Service Honolulu HI 
830 PM HST Wednesday Jan 7 2009 


Synopsis... 
high pressure will remain north of the state bringing moderate trade 
winds through Thursday. Winds will weaken and shift to the southeast 
Thursday night as a cold front approaches the islands from the 
northwest. The front will advance through the islands Saturday night 
and Sunday...bringing isolated thunderstorms and locally heavy 
rainfall. 


&& 


Discussion... 
rather typical trade wind weather prevails over the islands this 
evening. Clouds and showers embedded in the moderate trade winds 
are affecting mainly the windward and mountain sections this 
evening. Latest rainfall totals from the gages around the state 
showed not much precipitation in the past 6 hours...as the highest 
amount is only slightly over a tenth of an inch. Latest satellite 
imagery shows the usual distribution of clouds in the vicinity. Thus 
expect passing clouds and light showers to affect the windward and 
mountain areas of the island through the night into Thursday morning. 


The moderate trades are expected to last one more day. Then as a 
cold front from the northwest approaches the islands...a ridge will 
move over the islands...with winds becoming lighter and turning 
southeast. Land and sea breezes will become more prominent under the 
light wind regime...and the islands will experience a more 
convective type weather regime. Clouds and showers will develop 
under day time heating...while night time cooling will result in 
clearing. Air mass over the area is expected to remain stable...and 
thus precipitation will be limited. 


Winds will be increasingly gusty and turning more south by Saturday 
as the front nears the northern islands. The main rain band 
associated with the front is still expected to reach Kauai Saturday 
night...then advancing southeast through Oahu and Maui counties 
Sunday. Isolated thunderstorms as well as locally heavy rain are 
expected with the front. Believe the movement of the rain band is 
fast enough such that the threat of flooding is reduced. This front 
is expected to weaken when it reaches The Big Island by late 
Sunday...but there may be enough air mass instability for 
thunderstorms as well as locally heavy rain to develop over the 
island. 


There is quite a disagreement between forecasting models on what 
will happen after the frontal passage...with one model keeping 
westerly winds over the islands while the other has trade winds 
returning briefly. Shall await for future model runs before deciding 
if the current extended forecast is on track. 


&& 


Marine... 
the west northwest swell continues to slowly subside through rest 
of the week. The next northwest swell expecting by Sunday may 
produce surf above the advisory level across north and west facing 
shores through Monday. Surf along east facing shores will persist at 
moderate levels through Thursday under the moderate trade winds. 


&& 


Hfo watches/warnings/advisories... 
none. 


&& 


$$ 


Hui