Area Forecast Discussion
Issued by NWS
FXPQ60 PGUM 290728
Area Forecast Discussion
National Weather Service Tiyan GU
523 PM ChST Wed Mar 29 2017
.Marianas Synopsis... East winds, partly cloudy skies and
isolated showers prevail across the local area this afternoon.
Little change made to the forecast. Updated winds with new GFS model
data. East winds of 10 to 20 mph will prevail across the Marianas
through Friday night as high pressure centered to the north
increases the pressure gradient.
A weak shear line will produce mostly cloudy skies and patchy
showers over the local area through Friday night. Deep-layer
moisture will be shallow through the weekend so only expect partly
cloudy skies and isolated showers at that time. Trade-wind
convergence will increase clouds Tuesday night and Wednesday.
Observations this morning from Ipan, Ritidian and Tanapag buoys
indicate combined sea heights of 7 to 8 feet. There is a north swell
of of around 2 to 3 feet entering the area. The north swell has a
period of 11 seconds. Calculations predict surf on north facing
reefs of around 5 feet. Expect the north swell to increase to 4 feet
on Friday and remain that high through Friday night. This would
produce a surf of 5 to 7 feet on north facing reefs. There is also a
east trade-wind swell which will persist through the forecast. Surf
on east facing reefs is expected to be 6 to 8 feet through at least
Winds over the Marine area will be in the 20 to 25 knot range with
occasional gust to 30 knots on tonight. Winds will decrease slightly
Thursday but still expect frequent gust in the mid 20 knot range
through much of Thursday night. These winds are just high enough for
a small craft advisory. Observed combined seas, as mentioned earlier
are 7 to 8 feet. Model data show 7 to 9 feet through Friday morning.
There is a possibility that seas may briefly reach 10 feet...which
is small craft advisory criteria...through Thursday night.
Scattered to numerous showers and a few thunderstorms are seen
near Pohnpei and Kosrae ahead of a trade-wind surge. Northeast
trades will eventually push showers to the south of Pohnpei early
Thursday morning but showers will persist another couple of days
at Kosrae. Farther east, more clouds and a few showers are seen
south and east of Majuro. This area will expand and move westward
late in the week and into the weekend, keeping Kosrae mostly
cloudy with isolated thunderstorms. Most showers are expected to
stay south of Majuro, although the atoll could see an increase in
showers around Friday.
High surf advisory continues at Kosrae until Thursday evening as
trade-wind swell eventually subside. Also, both Majuro and Kosrae
may still see some inundation around times of high tides through
A disturbance southeast of Koror and Yap is generating widespread
cloudiness and showers in the area. Showers will increase at
Koror tonight and continue through Friday as the disturbance
drifts westward. Yap will see isolated showers and a small chance
of thunderstorms the next couple of days.
Showers at Chuuk will continue on through tonight but gradually move
off to the southwest by Thursday morning as stronger northeast
trades push the convergence boundary farther southwest and drier air
moves into the area.
Marianas Waters...Small Craft Advisory until 10 PM CHST Thursday for PMZ151>154.