Area Forecast Discussion
Issued by NWS
FXPQ60 PGUM 222242
Area Forecast Discussion
National Weather Service Tiyan GU
842 AM ChST Mon Jan 23 2017
Andersen Air Force Base Doppler weather radar shows scattered
showers southeast of Guam. Elsewhere, only isolated showers are
moving through the Marianas waters. The VAD wind profile shows
northeast winds of 8 to 12 knots just off the surface which
increase to between 20 and 30 knots through the lowest 13 thousand
feet of the air.
Shear line is gradually getting pushed back to the north. There
could be a period of scattered showers as it moves through again,
however it should be substantially less than last time. The winds
will be back, please see the Marine section about a new small
craft advisory. Clouds should remain overhead most of the forecast
period though. For a few hours this morning it will be rather
sunny, once the clouds move in though, they will be staying for a
while once again.
Buoys just went above 10 feet, and show north-northwest swell as
high as 8 feet. Therefore issued both small craft and high surf
advisories. Looks like the winds will be here through Wednesday at
least, and the waves through Thursday. As a first guess, went with
the Thursday time frame for the ending of the advisories. Waves
and surf should peak Tuesday and Wednesday.
A trade-wind convergence zone can be seen between 3N and 7N
stretching eastward from south of Chuuk at 150E thru the Date Line
to beyond 160W. Two trade-wind disturbances are embedded along
this zone, one over Chuuk at 153E and another one approaching
Majuro from 174E. The first disturbance will maintain showery
conditions near Chuuk until early this evening. After the passage
of this disturbance later tonight, slightly drier trades already
over Pohnpei just north of the convergence zone should also
provide a brief period of quieter weather for Chuuk. For Kosrae,
isolated thunderstorms near the zone will continue to affect the
island today. Farther east, showers and thunderstorms associated
with the second disturbance should persist near Majuro until late
this evening. As this second disturbance pulls farther westward,
it will also increase shower coverage for Kosrae by this evening,
Pohnpei and Chuuk on Tuesday.
The eastern portion of the convergence zone will keep a relatively
wet pattern for Majuro thru Tuesday evening, Kosrae most of the
week, Pohnpei and Chuuk thru midweek. Much drier northeast trades
might finally usher in fairer weather for Majuro near Wednesday,
Pohnpei and Chuuk near Friday.
Large trade-wind swell and wind waves will maintain hazardous surf
across the Marshall Islands until midweek, and Kosrae most of this
week. Combining with strong trade winds, conditions hazardous for
small craft will persist from Chuuk State eastward to the Marshall
Islands over the next several days.
Discussion for the Chuuk forecast is included in the Eastern
Micronesia section above.
A few thunderstorms related to an old shear line might spill over
Yap today. Otherwise, much drier northeast winds already over Koror
should also dominate Yap by this evening. By midweek, a trade-wind
disturbance currently upstream near Chuuk will arrive at the area.
Increasing low-level convergence near the northern part of this
disturbance will bring unsettled weather for both locatins during
the second half of this week.
Strong northeast winds and rough seas across the Republic of Palau
and western Yap State will sustain conditions hazardous for small
craft operation thru at least midweek. Large swell generated by
these winds near the old shear line will also cause high surf for
the region over the next several days.
GU...High Surf Advisory until 6 PM CHST Thursday for GUZ001>004.
Marianas Waters...Small Craft Advisory until 6 PM CHST Thursday