Area Forecast Discussion
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FXPQ60 PGUM 230802

Area Forecast Discussion
National Weather Service Tiyan GU
600 PM ChST Thu Feb 23 2017

.Marianas Synopsis...
The diffuse end of a shear line drapes across the Mariana Islands.
A trade-wind disturbance is seen southeast of Guam near 150E with
sporadic convection south of 10N.


The trade-wind disturbance and its associated wet weather is going
to pass south of Guam tonight and Friday. The diffuse shear line
will keep isolated light showers over our areas thru Friday
afternoon. Once the large ridge of high pressure currently northeast
of Minami Tori Shima has drifted northeast of Wake Island by Friday
evening, it should allow the shear line to dissipate over our area.
With abundant dry air above 850mb, decided to put slight chance of
showers for this weekend. Model guidance suggests mid to upper-level
winds might veer from the north to the southeast early next week.
If so, moisture should advect from the south over the Marianas and
increase the chance of showers for next week. Toward the next weekend,
model guidance also indicates a frontal boundary/shear line feature
extending southwestward into our region from a low pressure north
of Minami Tori Shima. It is way too early to even considering putting
this into the long-range forecast at this point.


A steady north swell along with trade-wind swell and wind waves will
maintain seas at 6 to 8 feet thru this weekend. Then increasing
trades will cause swell and wind waves to build higher next week. In
response, seas will rise to just below small craft advisory levels.


.Eastern Micronesia...
Satellite animation shows only weak trade-wind convergence over
eastern Micronesia with a series of very weak convective pulses
stretching from the Date Line to the southern Marshall Islands to
near Kosrae and across to Chuuk. The GFS and ECMWF models both
suggest only shallow convection except for Kosrae and that not
until Monday.

Combined seas will build by 1 to 3 feet across the region by Friday
night. We issued a high surf advisory for east exposures of Kosrae
for tonight. Seas will become hazardous for small craft Friday night
for Majuro and Sunday for Pohnpei. Lunar high tides and large seas
and surf could cause some minor inundation during high tides the
next several days at Majuro, particularly at low-lying northeast-
facing exposures.


.Western Micronesia...
The dry pattern of eastern Micronesia is setting up over western
Micronesia as well. While drier conditions are expected tomorrow for
Yap and Palau, deep moisture will return by Saturday, bringing
scattered showers and thunderstorms to Palau. Models suggest that
they will only skirt Yap, but we will see. Conditions should
improve at Chuuk by late tonight as an area of convection passes

Combined seas will increase to around 9 feet by Saturday at Yap and
Chuuk. Seas should stay just below small craft advisory here, but
will have to watch closely the next few days. Combined seas are
expected to remain below 9 feet in Palau.


Marianas Waters...None.


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