Area Forecast Discussion
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FXPQ60 PGUM 302101

Area Forecast Discussion
National Weather Service Tiyan GU
701 AM CHST TUE MAY 31 2016

Partly cloudy skies and gentle winds dominate the Marianas this
morning. A few showers are evident on PGUA WSR-88D data. Latest
IR satellite data shows very little cloudiness over the area
while water vapor imagery shows an upper-level low/TUTT cell to
the east of the Marianas.


No changes were made to the inherited forecast. Latest model runs
remain consistent with fairly dry conditions under the ridge axis
that will remain over the area. A weak TUTT cell is currently
located to the east of the Marianas. The latest model runs keeps
this system east of the islands until late in the week. By Friday,
this low begins to drift westward and will bring increasing
upper-level divergence over the Marianas, increasing the risk of
thunderstorms from Friday into the beginning of next week. The
limiting factors for thunder will be the fairly dry mid levels and
the actual positioning of the low as it moves across the islands.
Therefore, chose to maintain slight chance of thunderstorms for


.Eastern Micronesia...
A trade-wind convergence zone between 3N and 6N, extends east-
northeastward from south of Pohnpei at 157E to northeast of Majuro
at 177E. Sporadic convection associated with this zone will
continue to impact Kosrae and Majuro thru this evening. As this
zone gradually pushes westward, it might affect Pohnpei late this
evening as well. However, latest ASCAT streamline analysis already
shows a weakening trend on the trade winds across the region.
Reduced trade convergence should allow convection near Kosrae and
Majuro to decrease and produce mainly widely scattered showers
near Pohnpei on Wednesday. Another area of converging trade winds
can be seen farther east between 2N and 6N, stretching east-
northeastward from 180 to beyond 160W. This boundary is expected
to bring another round of unsettled weather to Majuro toward the
weekend, and possibly to Kosrae and Pohnpei by this weekend.


.Western Micronesia...
The leading edge of a moderate trade-wind surge can be seen east
of Chuuk near 154E. This feature will cause a period of showers
and even a thunderstorm or two near Chuuk tonight. Then a fair
trade-wind regime will follow on Wednesday. The remnants of a
trade-wind convergence zone currently over eastern Micronesia
might trigger a few more showers on Thursday. Otherwise,
relatively dry weather is anticipated thru Friday.

An upper-level trough curves northeastward from near Mindanao
thru 9N130E and a low centered between Koror and Yap at 10N136E to
beyond 16N150E. Meanwhile, a trade-wind disturbance is merging
against a surface ridge near Koror and Yap. Divergent flow south
of the upper low is enhancing scattered convection near Koror and
this will continue thru tonight. For Yap, modest subsidence near
the upper-level trough axis should keep showers at widely
scattered levels thru Wednesday. After the passage of this
disturbance by Thursday, light trade winds will provide partly
cloudy skies again.


.GUM Watches/Warnings/Advisories...
Marianas Waters...None.


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