Area Forecast Discussion
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FXPQ60 PGUM 180829
AFDPQ

Area Forecast Discussion
National Weather Service Tiyan GU
628 PM ChST Thu Jan 18 2018

.Marianas Synopsis...east to northeast trade-winds and a few showers
prevail across the Marianas this afternoon.

&&

.Discussion...
A few small changes made to the forecast. Did update of winds with
new model data. Also extended the Slight Chance of Showers until
Friday Night as opposed to through Tonight in the old forecast.

Dry Season weather pattern remains firmly entrenched across the
Marianas. Hardly any change is predicted through the forecast as
computer models continue to show no large scale weather features
passing over. The models continue to show a dearth of moisture as
deep-layer moisture will be lacking with 700 Mb relatively humidity
staying below 50 percent through at least next Thursday. Models show
the possibility of patchy clouds and showers passing over the
Marianas, possibly tonight. The clouds may possibly be the result of
weak trade-wind convergence. Any showers that form will be brief.

Winds of 10 to 15 mph will is predicted for tonight with 15 to 20 mph
Friday decreasing to 10 to 15 mph Friday night.

&&

.Marine...
Tanapag, Ritidian and Ipan buoys show sea heights around 8 feet.
Tanapag had earlier shown heights near 10 feet. Also the Tanapag buoy
did show maximum sea heights of 15 feet through part of the
afternoon. While the sea heights appear to be decreasing, felt that
they are too close to 10 feet so kept Small Craft Advisory out until
Friday morning.

Ritidian and Tanapag buoys shows the north swell around 4 to 5 feet
with a period of 13 seconds which should yield a surf height 7 to
8 feet. Again, this is too close for comfort, especially with the
variable nature of the swell over the last 24 hours, so kept out the
High Surf Advisory for north facing reefs until Friday morning.

Ipan had an east swell of 4 to 5 feet with an 12 second period. This
would equal a 7  to 8 foot surf on east facing reefs, although this
buoy did report a 6 to 7 foot swell this afternoon which would result
in a 9 foot surf. As the surf may decrease more slower than on north
facing reefs, kept out the High Rip Current risk on east facing reefs
through Friday afternoon. Models show a further decrease Friday night
and Saturday, so the rip current risk is predicted to return to
moderate.

&&

.Eastern Micronesia and Chuuk...
An east-west band of showers associated with low-level
convergence is already arriving at Majuro, and a surface trough
with scattered showers is slowly departing Pohnpei and showers
will approach Chuuk overnight. Fair weather will prevail at Kosrae
tonight and Friday. GFS Model shows the band of showers will
spread across the central Marshall Islands thru Friday, and areas
of showers will continue moving toward west and southwest during
the next few days. Rainfall amounts will be variable thru this
weekend across the region, and looks like the far northern
Marshalls will become increasingly dry during the coming weeks.

Combined seas will generally be 7-8 feet across the region, except
near 9 ft at times for Majuro. Surf Advisory remains in effect for
east facing shores of Kosrae, where east swell will keep surf at the
low end of hazardous for several days yet.

&&

.Western Micronesia...
Trade-wind convergence is producing scattered showers across Yap
State and that will continue overnight into Friday, then weather
will briefly improve at Yap. GFS shows more showers will arrive at
Yap from the east late saturday through Tuesday. At Koror; a
surface trough extends across southern Palau to near the Equator
southwest of Chuuk. Weather at Koror will be unstable while the
surface trough is nearby, although GFS indicates relatively quiet
weather at Koror on Saturday. Then, GFS depicts areas of showers
and locally heavy rainfall developing between Yap and western
Chuuk State by Sunday, and spreading westward across western
Micronesia Sunday through early next week.

Combined seas should range from 6 to 8 feet across the region, with
mostly east swell and wind waves.


.GUM WATCHES/WARNINGS/ADVISORIES...
GU...High Rip Current Risk through Friday afternoon for GUZ001>004.

     High Surf Advisory until 6 AM CHST Friday for GUZ001>004.

Marianas Waters...Small Craft Advisory until 6 AM CHST Friday for PMZ153-154.

&&

$$

Ziobro/Simpson



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