088
FXPQ50 PGUM 160816
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
616 PM ChST Thu May 16 2024

.Marianas Synopsis...
Satellite imagery shows scattered low level clouds across the
Marianas with isolated showers across the region. Latest altimetry
shows combined seas of 5 to 8 feet just east of the Marianas coastal
waters.

&&

.Discussion...

Key Messages:

* Slight changes with the short term forecast with scattered showers
  possible for Guam on Friday.
* Little change in confidence in regards to 93W.
* Seas should increase this weekend into next week. Seas could become
  hazardous for small craft.

Short term:
Generally, current thinking isn`t too different from the previous
discussion. A slight uptick in showers will be possible on Friday and
Friday night. With the mesoscale models being within range,
confidence was high enough to go scattered showers for portions of
Guam. Further north, the typical drier trade-wind pattern should
persist with isolated showers possible.

Long term:
Model solutions have converged some with the development of the
disturbance in western Micronesia, which may or may not be 93W. The
00z GFS trended weaker and further west with the storm system, which
is closer to the 12z ECMWF and EPS solutions. This would keep the
storm just south and west of the Marianas. With westward shifts,
better chances for rain may be restricted to Guam or completely
outside of the Marianas. See tropical systems section for more
details.

&&

.Marine...
Trade winds will be moderate to fresh through Friday night and will
become fresh over the weekend. A surface high pressure is dominating
much of the Pacific and is interacting with a tightening pressure
gradient across Micronesia that will lead to an increase in the trade
winds. Combined seas will remain between 5 to 7 feet through the day
on Sunday before increasing Sunday night into next week. A moderate
risk for rip currents continues across east facing reefs. Surf looks
to increase this weekend into early next week and a high risk for rip
currents could be possible for east facing reefs early next week. The
marine forecast heading into next week will remain somewhat dependent
on the path and intensity of the disturbance in Micronesia.

&&

.Fire weather...
Only 0.02" of rain has been recorded so far today. Without a wetting
rain occurring this evening, the KBDI will likely increase from 522
tonight, which is in the high category. Winds are generally expected
to remain below criteria the next few days. Isolated to scattered
showers associated with ripples in the trade winds should limit the
risk of rapidly spreading fires as well.

&&

.Tropical systems...
93W is currently located at 4.1N and 144.3E and remains a broad and
weak circulation. Latest guidance continues to slow development of
the system, with the GFS now showing a weak tropical storm or
depression as opposed to a full blown typhoon. A buffer circulation
near the equator appears to be supplying a west wind near 93W. This
is evident on the MIMIC TPW product. As this buffer circulation
interacts with 93W or the tropical wave behind it, it should give the
westerly wind component necessary to tighten of the circulation into
a more concentrate area. Guidance generally forms the storm around
5N145E and tracks northwestward towards Yap or just southwest of the
Marianas. Those in western Chuuk State, Yap State, Republic of Palau,
and the Marianas should continue to monitor forecasts for any changes
noted in the region.

&&

.Eastern Micronesia...
The Inter-Tropical Convergence Zone (ITCZ) has transitioned to more
of a zone of trade convergence across the Marshall Islands, while
still maintaining the ITCZ over towards Pohnpei and Kosrae, along
the back side of a buffer circulation approaching Chuuk. Multiple
trade troughs and surges in the trade winds will interact with the
convergent zone and continue to bring scattered to at times numerous
showers and isolated thunderstorms to the forecast points. As we head
towards early next week, the convergent zone weakens and becomes
more fragmented, with showers becoming more isolated. First at Majuro
by around Monday, then Kosrae Tuesday and Pohnpei possibly around
the middle of next week. Depending on the evolution and track of
potential tropical cyclone (TC) over by Chuuk next week, convergent
flow on the eastern flank of TC could keep shower and thunderstorm
potential elevated for Kosrae and especially Pohnpei. Models are also
hinting at the reemergence of the ITCZ building in from the east by
late next week.

Gentle to moderate trade winds are expected to persist through early
next week. Winds could be fresh at times for Majuro through Friday
night. Combined seas of 4 to 6 feet will continue for Pohnpei and
Kosrae, with seas of 5 to 7 feet expected at Majuro. Seas could rise
about a foot over the weekend, as an elevated swell emanating from a
distant storm system northwest of Hawaii arrives, then drop back
down early next week.

&&

.Western Micronesia...
The near equatorial trough (NET), and the evolution of a potential
tropical cyclone embedded in it, remains the focus for western
Micronesia for the next several days. The NET stretches east-
northeastward from near 1N130E to a weak circulation southeast of Yap
and Palau, Invest 93W, centered near 4N144E, then continues
southeast to another circulation southeast of Chuuk near 3N155E. The
strong convergence north of the trough and east of Invest 93W, will
generate scattered to numerous showers across Chuuk that look to
continue into the weekend, possibly into next week. Locally heavy
showers are a possibility, along with isolated thunderstorms.

A trade trough along the north side of the NET is passing through
Yap currently and towards Palau tonight. Scattered showers and
isolated thunderstorms expected for Palau through Saturday, but look
to stay south of Yap, where isolated showers prevail. A drier
pattern is expected. However, though this could change any day when
the NET actually begins to move back northward with the approach of a
possible TC, which the general trend is hinting by around midweek.
Have bumped up of shower and thunderstorm potential for Yap starting
Tuesday.

Invest 93W looks to meander between Yap and Chuuk through the
weekend, with another circulation southeast of Chuuk approaching
from the east. The general model trend is for a tropical cyclone (TC)
to develop around early next week between Yap and Chuuk and meander
off to the north and west. Depending on the track and intensity of
potential TC, shower and thunderstorm coverage could increase for all
three locations.

Palau will see combined seas of 3 to 4 feet over the next several
days, along with generally gentle winds. Seas of 4 to 6 feet and
gentle to moderate winds are on tap for Yap and Chuuk. Depending on
the track and intensity of potential TC, seas and winds could
increase for all three locations.

&&

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

&&

$$

Marianas: Williams
Tropical: Williams
Micronesia: Slagle