822
FXPQ50 PGUM 012017
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
617 AM ChST Thu May 2 2024

.Overnight Update...

&&

.Marianas...
Scatterometer shows the axis of a weak surface trough pushing west
of the Marianas. Low-level convergence trailing behind this has
generated patchy showers overnight, mainly across the CNMI.
Yesterday`s rainfall totaled to 0.03 inches at the Guam airport and
0.65 inches at the Saipan airport, further illustrating the focus of
showers over the CNMI. Based on satellite trends, remnants of a weak
surface trough will keep spotty showers in the area through this
afternoon. Model guidance indicates drier air moving into Tinian and
Saipan by the afternoon, clearing up the skies a little sooner than
Guam.

&&

.Eastern Micronesia and Chuuk...
In the short-term, the convergent trade-wind flow mentioned in the
previous discussion, has deepened to become a much more substantial
trade-wind surge across much of the region overnight. This is
expected to bring increasing shower coverage at Pohnpei, Majuro, and
especially Kosrae, where gusts may reach near gale-force in heavier
showers. While showers are expected to diminish slightly starting
tonight for Kosrae, a generally wet pattern is still expected to
continue afterwards. Meanwhile, a brief period of diffusive trades
ensued at Chuuk, allowing much more pleasant weather to develop
today. Otherwise, the marine forecast remains unchanged.

.Western Micronesia for Yap and Palau...
A generally unsettled pattern continues in western Micronesia.
Heavier showers at Palau were postponed to tonight; while sporadic
showers are likely in the afternoon hours today, shower coverage and
intensity is expected to increase once a convergence zone rebuilds
to the east and moves in tonight. These showers are expected to bring
gusts to 30 mph as well, but seas are not expected to be much
different to the previous forecast cycle. Meanwhile, the weather and
marine forecast remains mainly unchanged for Yap.

&&

.Prev discussion... /issued 553 PM ChST Wed May 1 2024/

Marianas Synopsis...
Mostly cloudy skies with scattered showers are seen across the CNMI,
with partly cloudy skies and isolated showers over Guam. Gentle to
moderate trade winds prevail across the Marianas. Altimetry data
shows seas between 4 and 6 feet.

Discussion...
A weak trade-wind trough is moving through the Marianas. This trough
brought scattered showers to the Marianas through the day, with Guam
seeing drier conditions this afternoon. As the trough continues to
slowly move west, expect scattered showers to remain over the CNMI
through tonight, with isolated showers becoming scattered over Guam
later this evening as a second round of showers move over the island.
A drier pattern will then move into the CNMI, with scattered showers
lingering over Guam through the day Thursday. By Thursday night, all
of the Marianas look to return to a dry pattern. Another uptick in
showers is possible Friday into the weekend as another, weaker trough
moves into the region. As this trough is weaker than the first
trough, expect showers to remain just below scattered. By early next
week, the very dry pattern looks to move back into the region.

Marine...
No big changes in the marine forecast. Combined seas of 4 to 6 feet
are expected to slowly subside to between 3 and 5 feet by Friday,
then build back to the 4 to 6 foot range around Sunday as a north
swell pushes into the region. Gentle to moderate trade winds will
continue into next week.

Eastern Micronesia and Chuuk...
ASCAT analysis shows a convergent trade-wind flow continues across
Micronesia from Chuuk State across Pohnpei and Kosrae States and the
southern Marshall Islands to the Date Line. Satellite shows areas of
scattered showers and isolated thunderstorms were over Chuuk State
and southern Kosrae State this afternoon, mainly south of 7N, while
the Northern RMI remains very dry. The synoptic-scale pattern is not
expected to change much in the coming days, except GFS Model does
indicate a few showers could eventually develop a little farther
north; with helpful showers possibly arriving at Majuro this weekend.

Moderate to fresh surface winds from the east to northeast and
combined seas of 5 to 8 ft will likely persist across the region,
with any larger waves mainly toward the northeast.

Western Micronesia for Yap and Palau...
ASCAT analysis indicates a very weak circulation south of Koror
roughly near 2.5N137E; embedded in a Near-Equatorial Trough (NET).
Also a surface trough was moving slowly westward across southeast Yap
State. Satellite shows showers were developing in large areas over
the Republic of Palau and over much of Yap State, although still
south of 10N for the time being. Models indicate that unsettled
weather and persistent surface troughing will remain over far western
Micronesia. Rainfall may be heavy at times as showers and locally
deep convection develops over the region through the next day or two
at least.

Winds will be gusty and seas choppy near heavier showers and
thunderstorms in the coming days. Otherwise, moderate surface winds
and combined seas of 4 to 7 feet are expected through this weekend.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...None.
MP...None.
Marianas Waters...None.
&&

$$

Marianas: Cruz
Micronesia: Montvila