Area Forecast Discussion


423 
FXPQ60 PGUM 112029
AFDPQ 
Area Forecast Discussion
National Weather Service Tiyan GU
625 AM ChST Tue Dec 12 2017
.Marianas Synopsis...East trade-winds and isolated showers prevail
across the Marianas this morning. 
&&
.Discussion...
Little change made to the forecast. Did update winds with new model 
data. Latest model data continue to show decreasing deep layer 
moisture through the day. Latest Water Vapor imagery hints at 
decreasing deep layer moisture inching in from the east validating 
the model projections. With drier air filtering expect only partly 
cloudy skies with isolated showers today. Models show that the dry 
air will persist over the area keeping the showers at a minimum
through Wednesday night.
An area of trade-wind convergence and recovering deep layer moisture
will generate isolated showers and thunderstorms Thursday through 
Saturday.
&&
.Marine...
Ipan, Tanapag and Ritidian buoys show sea heights around 5 to 7 feet. 
Satellite altimetry data shows 6 foot seas over the local area. All 
three buoys show an east to northeast swell. Ritidian and Tanapag 
buoys show a northwest swell. Model data does show both swells over 
the area through the forecast. The east swell will be high enough to 
generate a high rip current risk on east facing reefs through at 
least Wednesday afternoon while the north swell will produce a 
moderate rip current risk on north facing reefs through tonight.  
&&
.Eastern Micronesia and Chuuk...
IR satellite shows two distinct areas of showers and thunderstorms
this morning. The first is across Chuuk and Pohnpei to near 
Kosrae, and the second is east and southeast of Majuro. Showers 
near Chuuk and Pohnpei are associated with a surge of fresh to 
strong trades converging along the northeast edge of a near-
equatorial trough and weak circulation southwest of Pohnpei. This 
will remain nearly- stationary the next few days before eventually
heading WNW. The convergence zone near Majuro will spread 
westward, prolonging showery weather across the region a couple 
more days. Expect a drier pattern to develop across the region by 
the weekend. 
Large trade-wind swell and wind waves will maintain hazardous surf 
on Kosrae for several more days. Trade-wind swell and wind waves 
have subsided enough at Majuro to allow surf to fall below hazardous
levels, therefore the High Surf Advisory is no longer in effect 
there. Winds have subsided near Majuro and are no longer hazardous
to small craft, but seas will remain elevated. GFS shows fresh to
strong trades returning to Majuro by midweek.
&&
.Western Micronesia...
The circulation just west of Koror near 8N130E (96W) and the monsoon
trough extending east-southeastward from it remain near Koror and
just south of Yap. IR satellite animation shows only a few 
showers near Yap and Koror with most convection just west of Koror
and northwest of Yap. Showers are expected to gradually increase 
over the area the next couple of days as models indicate the 
circulation will be very slow-moving as it becomes better 
organized. This will prolong the duration of southwest to west 
monsoon flow in the region. Should this circulation develop faster
before it pulls away from the area, combined sea forecasts will 
likely need to be increased.
.GUM WATCHES/WARNINGS/ADVISORIES...
GU...High Rip Current Risk through Wednesday afternoon for GUZ001>004.
Marianas Waters...None.
&&
$$
Ziobro/M. Aydlett