Area Forecast Discussion
Issued by NWS
FXPQ60 PGUM 231959
Area Forecast Discussion
National Weather Service Tiyan GU
538 AM ChST Mon Oct 24 2016
.Synopsis...Northeast trade-winds and isolated showers prevail
across the Marianas this morning.
Did update winds with new GFS40 data otherwise no change to
current forecast. VAD wind profile indicted winds from the
northeast at around 10 to 12 mph. Models show the northeast winds
giving way to east winds later this morning. The east winds will
prevail through the week. Expect winds of around 10 to 15 mph
today and tonight. A slight increase in the pressure gradient over
the local area will cause a small rise in winds over the Marianas
Tuesday and Wednesday.
A dry season weather pattern will settle in through the week with
only partly cloudy skies and isolated showers expected. Trade-
wind convergence will bring in clouds and an increase chance of
showers next weekend.
Buoy data show seas between 3 to 4 feet this morning. There is an
east swell and Ritidian buoy did show a north swell. Models show both
swells persisting through the week. Expect surf on east facing reefs
to be 4 to 6 feet today. Surf on north facing reefs will be 2 to
4 feet but is expected to increase slightly Wednesday night.
A surface trough moving through Chuuk and Pohnpei States along
with an upper-level low near 13N162E are generating showers and
thunderstorms near Pohnpei, but south of Chuuk and north of
Kosrae. More showers and thunderstorms are present east of Majuro
near another trough. Convection will taper at Pohnpei around
midday, but will increase at Chuuk this afternoon and overnight.
Both GFS and ECMWF maintain a southeast to east wind flow pattern
with winds mainly light to gentle across the area while stronger
ENE trades will be found north of 10N. Showers are expected to
stay north of 10N, near the convergence boundary of these two
patterns. However, a few weak disturbances are expected to
temporarily develop across the area that will bring a slight
chance of thunderstorms at times from Chuuk State eastward to
Majuro over the next several days.
Seas will remain benign the next several days. Chuuk, Pohnpei and
Kosrae will see a small long-period north swell the next couple of
days. It will diminish by midweek.
Reasoning for the Chuuk forecast can be found under the Eastern
Micronesia section above.
A surface trough is seen east of Yap and Koror. Convergent northeast
winds west of the trough are causing showers to develop near Koror.
These will likely persist for the day with little movement. Both GFS
and ECMWF show a small circulation forming within the trough and
move it south of Koror by midweek. As a result, northeast winds at
Yap and Koror will shift to east by Tuesday. The presence of the
disturbance will maintain isolated thunderstorms at both locations
around midweek. Drier weather is expected later in the week, but
because winds will be light, have included a slight chance of
thunderstorms for both Yap and Koror after Thursday.