Area Forecast Discussion
Issued by NWS
FXPQ60 PGUM 240925
Area Forecast Discussion
National Weather Service Tiyan GU
725 PM ChST Fri Mar 24 2017
A thin shear line is draped across Tinian and Saipan. While the
light showers have resulted in little or no accumulation, the
cloudiness is somewhat increased. Otherwise, gentle to moderate
trade winds and combined seas of 4 to 6 feet prevail within the
Most numeric models are agreeing that the status quo will remain
largely in place for the next several days. The only real change
will be that the shear line should fade away, leaving the skies at
Tinian and Saipan similar to the mostly sunny at Guam and Rota.
However, most also agree that a very late season (almost
unseasonably late) shear line will approach late in the forecast
period. This is also reflected in the wave models, which build
from between 4 and 6 feet to more like between 6 and 8 feet.
There is still some uncertainty though. The Canadian model is the
most aggressive, brining higher winds as far south as Guam. The
NavGem is the least aggressive, hardly showing such a feature at
all, with the GFS and the ECMWF being between. This will be the
major forecast problem, with everything else being minor tweaks.
Anybody planning recreational boating activities for next weekend
should remain aware of the situation.
One trade-wind disturbance is moving westward away from Chuuk
this afternoon and second one is moving from across Kosrae State
toward Pohnpei State. Also, bands of trade-wind showers are
moving into the central and southern Marshall Islands. The
northern RMI remains dry. Models indicate the second disturbance
will move to near Pohnpei on Saturday and toward southern Chuuk
State over the weekend, mainly south of Weno. Bands of trade-
wind showers will continue near Majuro tonight and Saturday, move
over Kosrae this weekend, then to Pohnpei and Chuuk by early next
week. Periods of trade-wind convergence next week could trigger
more showers at times across the area.
A long-period north swell generated by strong to near-gale winds
southeast of Japan earlier will persist from Chuuk State eastward
to the Marshall Islands over the next several days. Meanwhile,
trade- wind swell and wind waves are anticipated to build by this
weekend across the region. This combination will cause seas and
surf to rise, and conditions need to be monitored for possible
High Surf and Small Craft Advisories. In conjunction with an
astronomical high tide cycle of 5 to 6 feet above Mean Low Low
Water levels early next week, coastal inundation is also possible
at Kosrae and Majuro.
Chuuk forecast discussion is included with Eastern Micronesia
Satellite shows spotty showers over Palau while the weather
remains dry at Yap this afternoon. Meanwhile, a trade-wind
disturbance with areas of scattered to numerous showers is moving
westward away from Chuuk State. Models indicate the disturbance
will continue moving westward with showers and isolated
thunderstorms at times for Yap and Koror this weekend, especially
for Koror. Models also indicate relatively wet weather could
persist into next week.