FXPQ60 PGUM 260802

Area Forecast Discussion
National Weather Service Tiyan GU
600 PM ChST Wed Apr 26 2017

.Marianas Synopsis...
East trade winds prevail over the Marianas this afternoon.
Tropical Storm Muifa is located over 650 miles west of Guam. Low-
level convergence east of the storm will produce periods of
scattered shower, mainly over Guam and Rota tonight.


A few things were changed in the forecast. Models indicated scattered
showers returning to the Marianas later tonight. GFS and ECMWF depicted
the showers mainly over Guam and Rota so split the zones to reflect
this thought. Had originally had the scattered showers beginning closer
to midnight but observations and satellite imagery showed scattered
showers already over these two islands. Kept the scattered showers
into the morning hours at these two locations. Even though it is a
low probability isolated thunderstorms are possible through at least
Friday. Patchy showers are also possible through Friday. Models agree
that showers should be isolated through much of the weekend.


Observations this afternoon from Ritidian, Tanapag, and Ipan buoys
indicate combined sea heights of between 3 and 5 feet. East
trade winds will be 10 to 15 knots through the weekend.

An east swell of 3 to 4 feet is expected through Thursday night,
decreasing by a foot on Friday. Ritidian and Tanapag buoys showed a
north swell. WW3 model guidance also showed this swell so added it to
the forecast. It will remain at 2 feet and gradually become northeast
by Thursday night before ending Saturday. Surf will be 5 to 7 feet on
east facing reefs with little change the next few days. The surf on
north facing reefs will be around 2 to 4 feet.

As the wind field around Tropical Storm Muifa is small and not
directed at the Marianas, do not expect any increase in surf on
west facing reefs as a result.


.Tropical Systems...
Tropical Storm Muifa is over 650 miles west of Guam this afternoon.
The storm is drifting west-northwest and is expected to turn to the
north Thursday morning and northeast by Thursday night. Winds near
the center are near 45 mph. It is predicted that the winds may
increase slightly before decreasing. Muifa will remain far away
from the local area and dissipate by the weekend.


.Eastern Micronesia...
A weak surface impulse between Chuuk and Pohnpei will maintain a
few showers near Pohnpei this evening, and Chuuk thru Thursday.
Slightly drier trade winds should promote fair weather near Kosrae
until Thursday evening. Then this same drier trades will also
pass thru Pohnpei on Thursday and Chuuk on Friday. Farther east, a
better organized trade-wind disturbance is progressing across the
Marshall Islands. This system is going to produce periodic
showers and a thunderstorm or two near Majuro thru Thursday
evening. It will create similar conditions near Kosrae and Pohnpei
toward the weekend, then Chuuk by the weekend. Afterward, much
drier fresh trade winds should usher in partly cloud skies for
Majuro and Pohnpei by this weekend, Chuuk early next week. For
Kosrae, trade- wind convergence along the southern extent of these
fresh trades might sustain unstable weather thru this weekend.


.Western Micronesia...
Forecast discussion for Chuuk can be found under Eastern
Micronesia above.

Tropical Storm Muifa (03W) is nearly stationary over the Philippine
Sea north of Koror near 13N135E. A gentle wind field well south of
Muifa should prolong pleasant weather near Koror thru Friday. The
slow movement of Muifa has allowed convergent south to southeast
winds feeding toward the storm to linger over Yap. This has led to
sporadic convection flaring up near Yap and this trend will continue
thru Thursday evening. Once Muifa has finally tracked farther
northward across the Philippine Sea on Friday evening, a surface
ridge should form over the area and promote dry weather for both
places. For next week, a relatively wet trade-wind pattern might
return to the region.


Marianas Waters...None.


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