966 
fxpq60 pgum 202031 
afdpq 


Area forecast discussion 
National Weather Service tiyan GU 
631 am chst Sat Nov 21 2009 


Synopsis... 
isolated showers are present across the marianas. An active monsoon 
trough remains south of the region...with intense convection near 
and west of Chuuk and well south of Guam...associated with a weak 
circulation just SW of Chuuk. 


&& 


Discussion... 
for the next 2-3 days...little change from the previous forecast 
with a trade wind surge passing through the marianas Sunday and 
Sunday night. Beyond that...models still in broad agreement on 
developing the circulation near Chuuk through Monday...then kicking 
it northwest at the marianas in the Tuesday-Thursday time frame. But details vary 
from model to model both in timing and track. European model (ecmwf) brings a well- 
developed dew point just south of Guam Wednesday...while GFS brings a poorly 
organized circulation just NE of Saipan on Wednesday. NOGAPS is slower 
and brings a dew point right over Guam on Thanksgiving day. 


While there seems to be a significant chance a tropical cyclone 
may affect the marianas near Thanksgiving day...the potential 
storm has yet to develop and much uncertainty remains regarding 
track...timing and potential intensity. Thus...still too early to 
put a tropical cyclone into the wind grids. But even with all the 
uncertainty...it does at least seem likely that showers will 
increase by Wednesday...so have added scattered showers for Wednesday-Thursday 
night. 


&& 


Marine/surf... 
Small Craft Advisory for both winds and seas will likely be needed 
for Sunday and Sunday night as winds increase to 20-25 knots and seas 
reach 10 feet. Jury is still out on a possible high surf advisory 
since swell is mainly from the east...and surf must reach 12 feet 
on east facing reefs for an advisory. Will need to watch ipan bouy 
closely tonight and Sunday. 


&& 


Eastern micronesia... 
satellite imagery indicates westerlies pushing into eastern 
micronesia south of a monsoon trough. Convection associated with a 
circulation near Chuuk has been building toward Pohnpei. Pohnpei 
has had scattered showers around marine zone all night but not 
over it. Models indicate possible short periods of scattered 
showers for Pohnpei through Tuesday but nothing definitive yet. 
Left isolated showers in the forecast but at some point it may 
need to be updated to scattered. Satellite and the models indicate 
fairly quiet weather throughout the forecast period for Kosrae and 
Majuro. 


&& 


Western micronesia... 
circulation near Chuuk will likely continue to develop and may 
become a tc in the next couple of days or so. Models show a slow 
movement that will likely place Chuuk within the rain shield for 
the better part of the forecast period. May have to update for 
winds and heavy rain in later periods to reflect an intensifying 
system. Meanwhile...an active monsoon pattern over Koror should 
keep scattered showers in the forecast into next week. Yap will 
remain far enough north of the monsoon trough axis to stay out of 
the main weather action. So trade-wind showers will be the rule 
through the forecast period. 


&& 


Gum watches/warnings/advisories... 
GU...none. 
Marianas waters...none. 
&& 


$$ 


Middlebrooke/devita 

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