Area Forecast Discussion
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FXPQ60 PGUM 230751

Area Forecast Discussion
National Weather Service Tiyan GU
551 PM ChST Mon Apr 23 2018

.Marianas Synopsis...
Partly cloudy skies, a few showers and moderate to fresh trade
winds prevail across the Marianas this afternoon. A trade-wind
disturbance/surface trough is seen east of the Marianas, east
of 150E. Buoy observations show combined seas around 5 to 6 ft.


A number of changes were made to the inherited forecast based on
the surface trough between 150E and 160E. Dry weather will persist
overnight but clouds will build in from the east Tuesday morning.
Expect isolated showers to become scattered by Tuesday night.
Westward motion with the trough has been slow so timing may need
adjustment but we can expect a period of more clouds and light
showers across the region overnight Tuesday. Drier weather will
return for Wednesday before convergence increases on Thursday
which could provide a slight uptick in showers Thursday. Models
indicate the next weather system for us will be another surface
trough/trade wind disturbance, now near the Marshall Islands.
Current timing brings more showers to the region Friday and


Seas will remain benign the next few days. A small north swell
tonight will build about another foot across the region by


.Eastern Micronesia...
Little change in the forecast discussion. An expanded north-south
orientated trough with several weak circulations noted in the
visual satellite imagery is expected to finally move west of
Kosrae by Tuesday and thus ending the period of scattered showers
that have been affecting the island for several days. In the mean
while these same showers have been very slow to break through the
ridge and move into the islands around Pohnpei. With a surface
ridge to the west...models are suggesting most of the energy will
pass north of Pohnpei and so I have only given the island one day
of wide-spread scattered showers.

The trade-wind disturbance just east of the Marshalls is the next
weather producer to affect the three islands in Eastern
Micronesia. However, in spite of its close proximity to Majuro the
GFS and ECMWF are in agreement to initially pass most of the
energy to the north of Majuro with just a brushing of
precipitation. Then with the leading edge approaching Pohnpei
the models suggest an amplification of the trough, likely
bringing scattered showers and isolated thunderstorms to all three
islands by the end of the week. This will be interesting to watch
and there is a suggestion that a series of circulations may
develop in the trough along 10N between Pohnpei and Majuro
bringing the winds back to southeast at Majuro and south or
possibly even southwest for Kosrae.


.Western Micronesia...
Expect uneventful weather for Chuuk for the next several days as a
surface ridge is sitting over the region with more active troughs
to the east and west. Weather from the approaching trough to the
east, discussed above should finally begin to affect the region
late Friday or Saturday. Timing of this event, if it occurs at
all, will become more clear as the week progresses.

Yap and Koror are also sitting under mostly fair conditions that
are expected to hold for most of the week. Models suggest the
weak circulation currently near 3N146E will stretch slowly towards
the northwest mostly likely losing its closed circulation while
pushing weather into Yap by Friday and possibly Koror by
Saturday. The signal is not strong so confidence of this trough
actually getting as far west as Koror is low.

Marine conditions remain benign for all stations this week.


Marianas Waters...None.


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