Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxpq60 pgum 242008 

Area forecast discussion
National Weather Service tiyan GU
608 am chst Sat Feb 25 2017

Marianas synopsis...
moderate to fresh trade winds and combined seas of 6 to 8 feet are
present across the marianas. Satellite and radar show only isolated
showers, mainly south and southeast of Guam.


little change is seen in the latest models, and the forecasts have
only been given a few tweaks. The European model (ecmwf) keeps a dry pattern in place
for the next 10 days, while the GFS, after a quiet period through the
first half of next week, brings in more active weather around mid-
week as a large but weak circulation develops near Palau and Yap.
This looks overdone, and prefer the quiet European model (ecmwf) for now. Hence, a
typical dry-season forecast for the next 7 days.


north swell is already starting to fall at the tanapag buoy, and this
trend should reach the ritidian buoy fairly soon. Thus, the surf
advisory looks good to come down during the day. Seas will likely
rise a bit the next few days, but this will be due to east swell, and
high surf is not expected after today.


Eastern micronesia...
satellite imagery shows quiet conditions across the region from Chuuk
eastward with the only showers and thunderstorms found well south...
south of 4n. Both European model (ecmwf) and GFS show a trade-wind convergence pattern
developing along 4-5n the next several days that will generate a long
band of showers and thunderstorms across the area. As convection
spreads northward, Kosrae will see increasing showers Monday, and
then Chuuk will see increased activity by Tuesday. Pohnpei will see
more cloud cover and isolated thunderstorms but latest models do not
show quite as much moisture for the time being. Will have to see how
subsequent model runs handle that area. Majuro will see a short
increase in showers early in the week, but the bulk of activity will
say well south and southwest.

Fresh to strong trades are seen across central and eastern micronesia
along with large trade-wind swell and wind waves. Winds hazardous to
small craft will persist at Chuuk through Sunday and at Majuro today.
Seas will be hazardous to small craft at Chuuk, Pohnpei, Kosrae and
Majuro for the next day or two. In addition, hazardous surf will
persist at Kosrae the next couple of days. A long-period north swell
will gradually subside by midweek.


Western micronesia...
a surface trough is moving through Yap state and toward Koror and is
bringing showers and thunderstorms to the area. Satellite imagery
shows most convection staying just south of 10n, leaving Yap along
the northern edge of the large cluster of showers and thunderstorms.
Models initialize well with this setup and show improving conditions
tonight at Yap, however, Koror will see thunderstorms lasting into
early Sunday morning.

In the Long Run, around 7 days out, GFS shows a broad circulation
developing near Yap and Palau with showers and thunderstorms across
much of the area. European model (ecmwf) shows a weaker circulation, but also much
closer to the Equator. Both models show strong north-northeast winds over the
Philippine Sea and a shear line/surface trof extending northeastward
to west of the marianas. This pattern looks similar to one 2 weeks
ago that brought strong winds, high seas and surf to both locations.
Will have to watch closely how later model runs handle this


Gum watches/warnings/advisories...
GU...high surf advisory until 5 PM chst this afternoon for

Marianas waters...none.

National Weather Service Glossary of Abbreviations