944
FXPQ50 PGUM 070914
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
714 PM ChST Thu Nov 7 2024

.Marianas Synopsis...
The latest Doppler radar loop shows precipitation is decreasing for
now across the Marianas. Seas are in the 4 to 6 foot range, with a
water temperature of 85 degrees at the Ritidian buoy.

&&

.Discussion...
It`s been an active day here as morning convection gave way to
afternoon tropical concerns. More on that is discussed in the
tropical section below. Overall, not much has changed. We adjusted
temperatures downward on a few days to account for periods of
increased cloud cover and rainfall.

&&

.Marine...
Seas are in the 4 to 6 foot range based on the latest altimetry data
and buoy observations, with a moderate risk of rip currents for our
northern and eastern reefs. For the most part that`ll hold true, but
seas and surf could increase a foot or so for Sunday into Monday.
Much of this is dependent though on how Invest 93W and another
tropical circulation, forecast to form near Chuuk develops, and
where and when both systems track, and at what strength. Thus,
things remain uncertain for much of next week. More on this is in the
tropical section below. For now, expect gentle to moderate winds to
persist.

&&

.Tropical systems...
Invest 93W from the Joint Typhoon Warning Center (JTWC), has been
upgraded to a moderate risk for development, meaning the development
of a tropical cyclone (tropical depression strength or higher) is
likely beyond 24 hours. We`ve had another great day of multiple
conversations (as always) and appreciate the coordination/teamwork.

Here`s what we "have a better idea" of; confidence is slowly
increasing for the potential for locally heavy rainfall and stronger
wind gusts with at least one tropical system, possibly two, sometime
next week. The operational GFS, NBM, and ECMWF, with the GEFS (20
members...or different forecasts, each with a slight initial
adjustment), and the an ECMWF ensembles (50 members of the same
described in the line above) have two developing trends. They, along
with some support from the NBM, portray 2 scenarios. The first is
that 93W strengthens over the next 36 hours (if not sooner) given
favorable conditions, as it passes by Majuro and through the northern
RMI (republic of the Marshall Islands), before turning west and
continuing until it gets near 14N or 15N and 150E (roughly 250 miles
east of Tinian and Saipan). Then, some of the GFS/ECMWF ensembles
turn it west-southwest, some keep it heading west, and some turn it
northwest, at varying rates of intensity.

Add into the mix, as this occurs, another circulation or two
potentially develop near Chuuk, and some members track it near/over
the Marianas as it heads west-northwest or northwest, at varying
rates of strengthening/intensity, and others combine both systems,
again at different rates of intensity, different timing, and
different locations.

So aside from wetter, cloudier, cooler conditions, what else can we
add to those expectations that are in the current forecast. Only that
confidence is growing (slowly) that some type/strength of system may
affect Guam and/or the CNMI. Stay tuned!

&&

.Eastern Micronesia...
Satellite imagery shows scattered to widespread showers and isolated
thunderstorms across eastern Micronesia. Combined seas range between
3 and 5 feet across Pohnpei and Kosrae and 5 to 7 feet across the
RMI.

An active pattern has setup across eastern Micronesia with
widespread locally heavy showers seen across Majuro. These showers
and thunderstorms are associated with a trough that will be moving
westward across the region over the next couple of days. Behind the
trough, quieter weather will temporarily settle across the region
with isolated to low end (30%) scattered showers possible. The
quieter conditions will be late this week into Saturday for Majuro,
this weekend for Kosrae, and early next week for Pohnpei. Model
guidance is showing an uptick in the ITCZ this weekend and into
early next week for eastern Micronesia. This would bring another
active stretch beginning at Majuro and then shifting towards Pohnpei
and Kosrae. Some uncertainty remains in how strong the ITCZ will
get, so PoPs were kept at high end (50%) scattered showers for now.

Combined seas vary greatly across eastern Micronesia with seas of 5
to 7 seen across the RMI while seas are 3 to 5 feet across Kosrae
and Pohnpei. Seas are forecasted to increase to 4 to 6 feet across
Kosrae tonight and Pohnpei on Friday. Winds were increased across
Kosrae for tonight as the axis of the trough moves to the north of
the coastal waters. Winds look to remain below small craft criteria,
but periods of hazardous conditions could be possible with
thunderstorms.

&&

.Western Micronesia...
A broad and weak near-equatorial troughs (NET) will be the dominant
feature over Yap and Palau through the weekend. However, moisture and
vertical lift is limited withing the trough and only expecting
isolated to low-end scattered showers, mainly for Yap where they
will see slightly enhances convergence due to the trade winds
flowing into the NET. An isolated thunderstorm potential expected for
Yap as well. Over towards Chuuk, expect increasing showers and
potential of thunderstorms beginning tonight and continuing through
the weekend as a potent trough and possible developing circulation
pushes in from the east. Heavy downpours and gusty winds could be
possible with stronger showers and thunderstorms, as have been
observed over Pohnpei and Kosrae today. The general model trend does
show the circulation developing near Chuuk Friday night or Saturday
and then strengthening as it pushes northwest of Chuuk in the general
direction of the Marianas by late weekend. However, those in Yap and
Palau should continue to monitor the forecast for any shift to the
south and possible impacts early to mid next week. Otherwise, current
thinking is for fairly benign weather conditions to continue next
week with mainly a lower-end potential for showers and slight chance
of thunderstorms for Yap and Palau. Chuuk may see a slightly better
potential for showers and thunderstorms as a surface trough or two
creep west out of eastern Micronesia, mainly around midweek.

Benign marine conditions should continue with light to gentle winds
and seas 3 to 4 feet for Yap and Palau. Slightly higher winds and
sea expected (gentle to moderate and 3 to 5 feet) for Chuuk.
Depending on the development and path of the potential tropical
disturbance that currently east of Chuuk, winds and seas could be
higher.

&&

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

$$

Marianas: Doll
E.Micronesia: Williams/Cruz
W.Micronesia: Slagle