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Area forecast discussion 
National Weather Service tiyan GU 
540 PM chst Friday Jul 18 2008 


Synopsis... 
pgua WSR-88D shows a line of showers associated with a low north 
of the marianas approaching from the north. They should continue 
to approach as the low sags south...reaching Saipan in the next 
few hours and Guam around midnight. 


&& 


Discussion... 
low which the GFS has been prognosticating has more or less formed 
as advertised. Gfs40 model still keeps the later showers north of 
our area. Little change to the previous grids except to refine 
them for the tonight period to add some timing details now that we 
can track the showers on radar. They are just entering Saipan 
waters around 4 PM and have tops around 43 thousand feet. Since 
the radar is now detecting 30 dbz as high as 35 thousand feet... 
some of the individual cells may be thunderstorms. 


Low should then move out to the west...remaining far enough to our 
north to keep US rather dry for this time of year. The ridge to 
the south of the low might even keep US drier than normal for 
liberation day. 


&& 


Eastern micronesia... 
low-level convergence is spread weakly across the area...mainly 
across the Marshall Islands. Moderately strong west-southwest flow 
aloft is shearing off the stronger convection...leaving only minimal 
risk of thunderstorms overnight. The GFS model indicates only minor 
changes during the next several days while weak troughs and trade 
wind surges move through the area. 


Increasing trade wind swells have already created combined seas 
between 6 and 7 feet over Majuro. They will be arriving at Kosrae by 
Sunday...and possibly cause a high surf event along Eastern Shores. 


&& 


Western micronesia... 
weak surface convergence persists over Palau and Yap. Latest GFS 
model indicates this pattern will persist...and locally strong 
convection may develop in the area by Sunday night or Monday. For 
the Chuuk area...trade-wind convergence will gradually spread into 
the area during the next couple days from the east. 


&& 


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


$$ 


Stanko/Simpson 

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