Area Forecast Discussion
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FXPQ60 PGUM 290734

Area Forecast Discussion
National Weather Service Tiyan GU
238 PM ChST Mon May 29 2017

.Marianas Synopsis...
Satellite imagery shows a few clouds and showers moving through the
Marianas with a larger cluster of showers near Saipan and Tinian.
Island convection generated a few more clouds today and was evident
in cloud streaks extending WSW from the islands. Composited
precipitable water imagery indicates increased atmospheric moisture
near the Marianas, although much deeper moisture remains south of
10N. Buoys show seas between 3 and 5 feet.


Just minimal changes were needed to the forecast as little has
changed in the outlook for the next week. Increased atmospheric
moisture will promote isolated showers the next few days as opposed
to the bone-dry, zero rain days we saw last week. Models still show
an uptick in moisture and clouds Tuesday night and Wednesday from a
small low-level trade-wind disturbance, but clouds will decrease
again by Thursday. Both GFS and ECMWF show increasing moisture near
the Marianas after Sunday, although at slightly different times and
location, but the trend suggests more moisture creeping northward
beyond 10N. This trend seems to be in response to upper-level flow
with the various models bringing an upper-level trough and
circulation near the area. Of course, exactly where these features
are located will play a large role in just where the showers would
develop. For now will hold on to the mostly cloudy skies early next
week, and watch subsequent model runs for consistency in plot
development. In the meantime, surface winds will decrease the next
couple of days. With that increased atmospheric moisture in the area,
we could see island convection leading to some localized slow-moving
showers in the mid-day to early afternoon hours. Seas will fall
another foot or so with surf falling accordingly. There will be a low
risk of rip currents beginning Tuesday, continuing through the week.


.Eastern Micronesia...
The afternoon satellite imagery showed mainly isolated showers over
the eastern half of Micronesia. An area of scattered showers and
isolated thunderstorms could be found southeast of Majuro. Models
show this area not moving much and eventually decreasing in coverage.

Isolated showers are expected across the eastern half of Micronesia
the coming week. An upper-level trough, now located north of 15N this
afternoon, will gradually push southward during the week. Weak
trade-wind convergence will also be present and the combination of
these features will produce mostly cloudy skies and patchy showers
over the area the second half of the week.


.Western Micronesia...
Trade-wind convergence is generating an area of scattered showers and
isolated thunderstorms south and southeast of Palau. These showers
will develop northward and push across Palau late tonight through
Tuesday night. High pressure will build into western Micronesia west
of 140E. This will keep skies partly cloudy across Palau Wednesday
through Friday.

Yap will remain north of the area of showers and only partly cloudy
skies and isolated showers are expected there tonight. The ridge of
high pressure mentioned above will extend the fair weather at Yap
through Tuesday night. Only partly cloudy skies and isolated showers
are expected at Chuuk tonight through Tuesday night as high pressure
is already present there. Weak trade-wind convergence will produce a
few more clouds and thunderstorms at Yap and Chuuk the second half of
the week.


Marianas Waters...None.


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