Area Forecast Discussion
Issued by NWS
FXPQ60 PGUM 240800
Area Forecast Discussion
National Weather Service Tiyan GU
600 PM ChST Mon Apr 24 2017
A mostly cloudy sky with moderate wind continue across the
Marianas. Scattered showers are evident across Guam, with
isolated showers further north. A tropical depression is located
to the southwest of Guam. Combined seas of 4 to 6 feet are
generally expected through midweek before decreasing.
Latest satellite imagery shows a tropical depression about 400
miles southwest of Guam and moving slowly west-northwestward.
Pockets of moisture associated with this system has been moving
mainly toward Guam and bringing scattered showers. Lesser rain was
occurring over the CNMI. As has been the case for the last few
days, the GFS remains wetter than the ECMWF. The wetter forecast
for Guam was correct today, but probably not as much for the other
Marianas Islands. Based on the available moisture and looking at
satellite trends and other available data, the only significant
change that was made to the forecast was to extend scattered
showers into Tuesday morning.
Beyond that, the guidance continues to diverge and have left the
forecast unchanged for now with shower and thunderstorm chances
becoming more isolated as the week progresses.
Latest ASCAT satellite imagery indicates trade winds from Chuuk
State eastward to the Marshall Islands have decreased to moderate.
Reduced trade-wind convergence has allowed convection to gradually
weaken near Kosrae and this trend should continue tonight. Slightly
drier northeasterly trade winds should maintain fair weather near
Chuuk thru Tuesday, Pohnpei until Tuesday morning. Then residual
trade-wind convergence shifting westward from Kosrae might trigger a
few thunderstorms for Pohnpei by Tuesday and Chuuk by Tuesday night.
Farther east, the leading edge of a fresh trade-wind surge in the
form of a disturbance is moving across the eastern Marshall Islands
this evening. Therefore, expect periodic showers and possible
thunderstorms near Majuro thru Tuesday. As this disturbance and
surge pull farther westward, showers will increase once again for
Kosrae by late Tuesday night; Pohnpei and Chuuk near midweek. After
the passage of this disturbance, much drier northeasterly trades
might finally dominate the weather near Majuro by midweek, and the
rest of the region toward the weekend.
Forecast discussion for Chuuk can be found under Eastern Micronesia
A developing tropical depression can be seen north-northeast of Yap
near 12N139E this evening. Much weaker westerly to southwesterly
flow south of the depression along with drier air above 750mb will
sustain a relatively dry regime near Koror and Yap thru Tuesday
night. As the depression pulls farther northward over the Philippine
Sea and becomes better organized, a surface ridge should form over
the area and promote pleasant conditions thru Thursday. By this
weekend, increasing mid-level moisture might trigger a few more
showers near both places.