NWS Guam wrote its last area forecast discussion before the first event at May 16, 12:14 PM UTC, 1 hour 46 minutes earlier.
Area forecast discussion, May 16, 12:14 PM UTC, 1 hour 46 minutes before
Area Forecast Discussion...CORRECTED
National Weather Service Tiyan GU
1014 PM ChST Tue May 16 2023
CORRECTED TYPO IN TROPICAL SYSTEMS SECTION
.Marianas Synopsis...
Very isolated showers and moderate trade winds are seen across the
Mariana Islands as the dry pattern maintains through tonight.
&&
.Discussion...
Forecast remains the same, dry tonight and tomorrow. It is expected
to be less dry the remainder of the week but still isolated showers
for most of the week. Late tomorrow and Thursday, there is a chance
of a slight uptick in showers from a pocket of moisture, but still
don't think it's enough for scattered showers.
&&
.Marine...
Combined seas are expected to remain in the 3 to 5 ft range, then
starting around Thursday, background trade swell and north swell
increases through Friday to build seas up to 6 ft for Guam and Rota
and up to 7 ft for Tinian and Saipan coastal waters. Latest Ritidian
buoy indicated north swell turning north-northeast. Models show swell
direction turning north again around Friday.
&&
.Tropical systems...
A broad, monsoon-like pattern remains anchored across western
Micronesia. Models remain persistent with the development of a
circulation over this pattern, somewhere from southern Yap State to
south of Weno, Chuuk. The latest run of the GFS and ECMWF show this
feature developing and moving toward the northwest, with both models
being within about 60 miles of each other at he 210 hour point. The
GFS remains the most aggressive with the feature, showing a strong
TC developing over the weekend while the ECMWF remains a bit weaker.
However, this time frame is a bit too far out to rely on these
deterministic models. The ensembles show the same feature developing
over the the same region with the main difference being the timing.
Both the NBM and GEFS show the system strengthening a bit later than
the GFS and ECMWF. This scenario will continue to be monitored
closely over the coming days, while we watch for any indication of a
change in patterns or timing.
A weak circulation, now JTWC Invest 96W, is centered near 7N137E. 96W
is not expected to become a significant tropical cyclone until it
moves well west of Palau. Latest model guidance shows 96W moving
west-northwest with little or no development over the next several
days. What 96W will do is maintain a wet pattern over Yap through the
end of the week and over Palau through the weekend. Invest 96W will
continue to be monitored over the next few days for any changes.
&&
.Eastern Micronesia...
A band of convergence is now seen to the southwest to south of
Pohnpei, with most of the convection associated with the band seen
near and west of Pohnpei. This feature is expected to maintain
convection across Pohnpei through the next couple of days as it
drifts north. Showers are developing a bit farther north of the
convergence band, near Kosrae. As the band of convergence remains
active, a series of trade-wind troughs are expected to move through
the region. This will keep shower coverage elevated through the
first part of next week at Pohnpei. However, the convergence is
expected to decrease near Kosrae, which will allow showers to
decrease there over the weekend. Pohnpei should see the greatest
shower coverage Friday night into Saturday night as a circulation
develops near Chuuk, resulting in stronger convergence over the
island.
Farther east, Majuro is currently in a dry pattern, with only partly
cloudy skies and spotty showers. Another band of convergence is seen
well south of Majuro, near 1N to 3N from 165E to beyond the Date
Line. The strongest convergence is seen just east of the Date
Line near 3N to 4N. An approaching trade-wind trough east of the
Date Line will help pull the maximum convergence far enough north to
increase convection across the Marshall Islands, resulting in
scattered showers at Majuro Thursday night into the weekend. By
Sunday, these features will farther west and south, allowing a dry
pattern to return to Majuro.
Little change expected in marine conditions, with a fairly benign
marine pattern continuing for the next several days.
&&
.Western Micronesia...
A monsoon-like trough stretches southeastward from near 10N130E to a
weak circulation, Invest 96W, centered near 7N137E, then continues
southeastward to end near the equator at 150E. 96W is expected to
slowly drift west-northwestward, while the trough drifts north, over
the next several days. A band of stronger convergence is seen north
of the trough and 96W, near Yap, as well as south of the features,
near 2N. As the trough drifts north, the convergent band over yap
will move away from Yap, allowing a drier pattern to move in there
around Friday morning. The trough, 96W and the southern band of
convergence are expected to maintain a wet pattern across Palau
through the weekend.
For Chuuk, the western end of a band of convergence is seen across
the state. Farther east, a series of weak trade-wind troughs are
making their way west into Chuuk. These features will produce
convection across Weno through the next couple of days. later in the
week, near the weekend, models continue to indicate the development
of a circulation somewhere in the area of southern Yap State to south
of Weno, Chuuk. This looks likely to occur, though the intensity of
this circulation remains questionable. Either way, it looks likely
that showers and thunderstorms will continue across the region into
next week, with showers likely beginning Sunday. For more information
on this scenario, see the Tropical systems section, above.
Little change expected in the marine conditions over the coming week.
This could change if Invest 96W develops unexpectedly or if a
circulation develops earlier than expected near Chuuk.
&&
.GUM WATCHES/WARNINGS/ADVISORIES...
GU...None.
MP...None.
Marianas Waters...None.
&&
Marianas: Hong
Micronesia: Kleeschulte