Area Forecast Discussion
Issued by NWS
FXPQ60 PGUM 090819
Area Forecast Discussion
National Weather Service Tiyan GU
620 PM ChST Fri Dec 9 2016
.Synopsis... East trade-winds and isolated showers prevail
across the Marianas this afternoon.
Only a few minor changes made to the forecast. Did update winds
through the forecast with newer GFS model data.
Satellite imagery this afternoon shows a patch of clouds to the
east of the Marianas. This area is associated with a weak surface
trough. Models do show patches of showers increasing over the
Marianas after midnight tonight and persisting through the day on
Saturday. Deep layer moisture is not too high so just expect
periods of mostly cloudy skies while keeping shower coverage
Models show another surface trough pushing across the Marianas on
Monday. Scattered showers are expected over the local area early
Monday morning. Low-level convergence in the wake of the trough
will keep showers scattered through Monday night.
Trade-wind convergence will produce another period of mostly cloudy
skies Wednesday night through Thursday night. Some models hint at
scattered showers at that time...but not too certain of this at
this time so left showers isolated.
Winds will average between 10 to 15 mph through much of the forecast.
Expect winds of 10 to 15 knots through Monday with a brief
increase to between 10 and 20 knots Tuesday. Buoy data show seas
between 4 and 6 feet this afternoon. Models show the seas
remaining at this height through the weekend.
An east swell will prevail through the forecast. WW3 model shows
a north swell entering the area tonight and persisting until
Sunday morning. This swell will range between 1 to 2 feet. Another
north swell is predicted Wednesday through Friday at around the
As the swell will change little through the weekend, expect surf
on east facing reefs to be between 6 and 9 feet and 4 to 7 feet
on north facing reefs.
Two weak trade-wind disturbances will continue to maintain some
showers and possible thunderstorms near Chuuk thru Saturday
evening, and Pohnpei thru tonight. Then drier northeasterly trades
should usher in a period of fair weather for Pohnpei by Saturday,
and Chuuk on Sunday. Farther east, a weak circulation and
associated surface trough can be seen southeast of Kosrae and just
east of Majuro. These features are gradually progressing westward
and wet weather related to them should move over both locations
later this evening. This same wetness will then reach Pohnpei by
Sunday afternoon, and possibly Chuuk on Monday. Modest convergent
trade winds in the wake of these feature might keep lingering
showers near Majuro and Kosrae thru this weekend, Pohnpei thru
Monday and Chuuk thru Tuesday. Toward midweek next week, much
drier fresh northeasterly trades should push this convergent zone
southward and return partly cloudy skies to all locations except
Kosrae. Depends on how far south the convergent zone will shift,
it could stay close enough to Kosrae and maintain clouds and a few
Reasoning for the Chuuk forecast is included in the Eastern
Micronesia section above.
A weak and broad circulation is expected to persist southeast of Yap
over the next several days. Relatively drier trades north of this
circulation should keep showers at isolated category near Koror and
Yap thru Saturday. By Saturday night, increasing mid-level moisture
along with a series of weak trade-wind disturbances coming from the
east will introduce a wetter regime for the area which will last
into next week.