Area Forecast Discussion
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000
FXPQ60 PGUM 160630
AFDPQ

Area Forecast Discussion
National Weather Service Tiyan GU
430 PM ChST Sun Dec 16 2018

.Marianas Synopsis...
Mostly cloudy skies with isolated showers and fresh to strong trade
winds prevail across the Marianas this afternoon. Scattered to
numerous showers are evident on satellite to the east of the islands.
Latest buoy observations show seas between 8 and 12 feet.

&&

.Discussion...
Latest ASCAT analysis shows a surface trough to the east of the
Marianas. This system is slowly approaching the islands. A band of
weak convergence in advance of the trough will bring scattered
showers to the islands this evening through late Monday morning. As
the trough approaches the region, scattered showers are again
expected Tuesday and Tuesday night. Another trough and possible weak
circulation will then move toward the region on Thursday, bringing
yet another round of scattered showers to the area. Overall, a very
unsettled pattern is likely for the remainder of the week.

&&

.Marine...
Latest buoy observations show seas between 8 feet at Ipan to near 12
feet at Ritidian. An increasing north component of swell is evident
at Ritidian, with a north swell of around 6 feet. Based on the buoy
reports and the latest model guidance, decided to extend the Small
Craft Advisory through Thursday afternoon, as well as the High Surf
Advisory and High Risk of Rip Currents. Also extended the High Surf
Advisory and High Rip Current Risk to include north facing reefs
tonight. The north swell should be short lived, beginning to subside
over night.

&&

.Eastern Micronesia and Chuuk...
A cold front progressing eastward from near Minami Tori Shima has
weakened the ridge of high pressure northeast of Wake Island this
morning. In response, trade winds from Chuuk eastward to the
Marshall Islands have reduced. This will allow gentle southeasterly
winds and slightly drier air at mid levels to sustain pleasant
conditions near Chuuk thru tonight. Weaker trade-wind convergence
has also caused widespread convection near Pohnpei, Kosrae and
Majuro earlier to decrease. Nevertheless, a surface impulse embedded
along the trade-wind convergence boundary near 165E can still bring
periodic showers and thunderstorms to Kosrae thru Monday evening,
Pohnpei thru Tuesday, and Chuuk Monday night and Tuesday. For
Majuro, modest convergent trades can still spark a few showers and
thunderstorms there thru tonight. By Monday, zonal flow should
provide a period of drier weather for the capital. This same pattern
should also reach Kosrae by Tuesday, Pohnpei on Wednesday and
possibly Chuuk after midweek. Another dome of high pressure
currently over Japan will slide eastward over the next several days,
passing northeast of Wake Island near midweek. This feature can
channel fresh trade winds toward the region again and resurrect
trade-wind convergence across all locations for the second half of
the week.

Residual trade-wind swell will maintain hazardous surf from Chuuk
eastward to Kosrae States thru this evening then fall below advisory
levels on Monday. For Majuro, surf has dropped from dangerous to
hazardous levels last night but should remain hazardous thru at
least midweek. Conditions near Majuro will also be hazardous for
small craft operation thru at least midweek.

Trade winds and seas are both subsiding across the Northern Marshall
Islands. This trend will continue thru Tuesday but seas will remain
hazardous for small craft operation until Tuesday. Surf will also
stay hazardous along north and east facing shores thru Monday
evening.

&&

.Western Micronesia...
Fair weather has maintained its grip on Koror today, but showers and
thunderstorms are found near Yap to the north and east. A wetter
trade wind pattern is seen in visible satellite imagery from near
Yap, northeastward to the Marianas. This moisture is riding around
the northern half of a weak circulation west of Yap and Koror.
Models show more moisture near Yap over the next 24 to 36 hours, but
showers will spread to Koror as the circulation shifts westward. GFS
model shows a modest trade-wind convergence boundary will prolong an
unsettled pattern for the end of the week.

The large trade wind swell continues to subside across the region,
but a north swell will maintain hazardous surf at Yap through Monday
morning. Wave Watch model and altimetry suggests surf is and should
stay below hazardous levels the next couple days at Koror.

&&

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

     High Surf Advisory until 6 PM CHST Tuesday for GUZ001>004.

Marianas Waters...Small Craft Advisory until 6 PM CHST Tuesday for
 PMZ151>154.

&&

$$

Kleeschulte/M. Aydlett


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