Area Forecast Discussion
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FXPQ60 PGUM 260733

Area Forecast Discussion
National Weather Service Tiyan GU
535 PM ChST Sun Feb 26 2017

.Marianas Synopsis...
A weakening cold front is north of the Mariana Islands near Iwo To
Island at 23N. A few weak trade-wind disturbances can be seen on the
latest visible satellite imagery. One is passing through our area,
two more upstream near 153E and 167E.


The current disturbance will trigger a few spotty light showers for
the Marians this evening. The other two will also bring similar
conditions thru midweek. Latest model consensus still suggests
interaction between a low-level circulation near Yap and a shear
line/frontal zone digging southward toward the Marianas after midweek.
However, latest model runs are backing off on both precip and
positions of the features. The circulation might form farther north
of Yap which could cause the shear line to stay over the northern
CNMI most of the time. With much uncertainty still exists, no need
to make any major changes on the current long- range forecast.


Persistent trade-wind swell and wind waves will keep seas near 7 to
8 feet across the Marianas most of this week.


.Eastern Micronesia...
Satellite imagery from this afternoon showed an area of scattered
showers and isolated thunderstorms south of Pohnpei and near Kosrae.
These showers are produced by trade-wind convergence and will cause
mostly cloudy skies, scattered showers and isolated thunderstorms
at Kosrae tonight through Monday night. This area will gradually move
northward and bring scattered showers and isolated thunderstorms
Monday night through Wednesday at Pohnpei.

Trade-wind convergence will also increase further east towards
Majuro. While showers may increase Monday and Monday night, overall
coverage will remain isolated, so only expect mostly cloudy skies
and isolated showers there tonight through Tuesday night.

Scatterometer data from this morning showed an area of 20 to 25-knot
winds over Kosrae and hinted at the same over Pohnpei. The models
keep the winds this high at Kosrae through tonight and at Pohnpei
through Monday night. Winds this high are a hazard to small craft.
Seas will also be hazardous to small craft at Kosrae tonight and
at Pohnpei through Monday night.

Even though seas at Majuro are expected to remain below small craft
criteria, inundation of up to one foot is possible along northeast
and east facing shores through Monday night. This is the result of
persistent trade-wind swell and the higher tides generated around
the time of the new moon. The same trade-wind swell will produce
hazardous surf on north and east facing reefs of Pohnpei and Kosrae.


.Western Micronesia...
A near-equatorial trough stretched across western Micronesia south of
Palau, Yap, and Chuuk. Activity along this trough will remain south
of these three locations for the next few days. This will change by
Tuesday as models show showers increasing and expanding northward.
Expect scattered showers and isolated thunderstorms first at Chuuk,
beginning Tuesday and persisting through Thursday. The scattered
showers and isolated thunderstorms will move into Palau and Yap
Wednesday and stay at these two locations through at least Friday.

The GFS and ECMWF both depict a circulation forming on the trough
eventually being located south of Palau sometime on Wednesday. The
circulation will be slow to move and the models differ on its
location the second half of the coming week. GFS has it very close
to Palau Friday while the ECMWF keeps it south of that location.

Scatterometer data from this morning showed an area of 20 to 25-knot
winds just north of Chuuk. However, the models keep the wind gust
potential up to 25 knots. These winds, which are hazardous to small
craft will persist there through Monday night. Combined seas at Chuuk
will be between 8 and 10 feet tonight through Monday night, which
will also be hazardous to small craft.


Marianas Waters...None.


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