Area Forecast Discussion
Issued by NWS
FXPQ60 PGUM 290552
Area Forecast Discussion
National Weather Service Tiyan GU
337 PM ChST Mon Aug 29 2016
Dry conditions persist across the Marianas, except for Guam, where
an island thunderstorm is dropping heavy rain over the northern
third of the island. Winds are light from the southwest, and the
Ritidian buoy is reporting seas of 6-7 ft.
GFS and ECMWF are keeping winds light through the week, but
directions change with each model run, especially the GFS. Stayed
with the W-SW wind regime of the previous forecast, since changes
in the new model run are dependent on very weak and perishable
features in the model winds. One of these features in the GFS
tries to bring in scattered showers Wed afternoon and night, but
ECMWF has little or nothing, and will stay with isolated showers.
Seas have been slow to decrease, but may finally be starting a
slow decline. Kept the High Surf Advisory going through Tuesday,
but it may come down early tonight or tomorrow morning.
Light and variable wind flow is seen across the region, particularly
just north of Chuuk, Pohnpei and Kosrae to around 20N. Models show
this pattern of light and variable winds dropping southward over the
forecast points the next couple days. Convergence near weak surface
troughs will generate a few showers and thunderstorms around
midweek, but still with the absence of any discernible weather
features. An upper-level low centered near Pohnpei this afternoon
will head west, allowing drier weather to filter in to Chuuk by
Tuesday. Weak trade winds will try to wedge in from the east
Wednesday and Thursday. Models do show an uptick on showers in
this time frame as the trade winds converge on the light and
variable winds across the region.
Wave models still show a long period NW swell building in from
distant Typhoon Lionrock, near Japan. Surf will be elevated along
north and west facing exposures across the region but will keep
below advisory levels. Also expect slightly elevated seas during the
upcoming new moon phase the next few days.
A ridge will maintain fair weather at Yap and Koror at least through
Wednesday. GFS model depicts a weak surface trough over the islands
tonight, generating isolated showers and thunderstorms...but VIS
satellite imagery shows this trough just northwest of both
locations. Both ECMWF and GFS models show fairly light winds...at
times, variable, on Wednesday and Thursday. Similar to the
east...no discernible weather features are depicted through the
end of the week, but models do show a gradual return of the
southwest winds by the weekend at both Yap and Koror.
GU...High Surf Advisory until 6 PM CHST Tuesday for GUZ001>004.