105
FXPQ50 PGUM 162151
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
751 AM ChST Sat Apr 17 2021

.Marianas Synopsis...
East winds prevail over the Marianas this morning. Satellite imagery
shows a few clouds and showers over the area.

.Discussion...
A few small changes made to the current forecast. A ridge of high
pressure could be found over the Marianas this morning. This ridge
and shallow levels of moisture will keep showers to a minimum
through Monday night. Light winds and a slight increase in moisture
combined with daytime heating will equal a chance of afternoon
showers over the islands Tuesday through Thursday. Despite the slight
increase in moisture the Precipitable Water index will remain
relatively low so that afternoon thunderstorms are less likely.

&&

.Marine/Surf...
Ritidian and Tanapag buoys showed seas around 6 feet. Models depict
seas between 5 to 7 feet the next few days. Both buoys had a
northeast and a southwest swell. The northeast swell will persist
through the forecast. The southwest swell is from distant Typhoon
Surigae and will gradually shift to the west as the typhoon moves
northward. Both swells will produce a moderate rip current risk on
all reefs. The swell from Surigae may become a little larger as the
system increases in strength. The typhoon is quite distant but the
swell that reaches the Marianas may briefly become high enough to
produce hazardous surf on west facing reefs by the middle to the
week.

&&

.Fire weather...
The KDBI has increased to 709 today. A wetting rain is not expected
the next few days. Winds are expected to remain below Fire Advisory
criteria although dry conditions will be favorable for spot fires.
Afternoon showers may become scattered Tuesday through Thursday
which may produce a wetting rain.

&&

.Tropical systems...
Typhoon Surigae is moving away from Palau this morning. Satellite
imagery show that the typhoon has intensified slightly through the
morning and models show that it will continue to strengthen though
Sunday. The current forecast track indicates the typhoon is predicted
to remain on a northwest track then turn northward Tuesday.
Scatterometer data from late Friday night showed the 35 knot wind
radius near Palau and that was why the Typhoon Warning for Kayangel
and Tropical Storm Warning for Koror were left up early this morning.
As the typhoon has moved further away then so has the wind radii and
so the warnings have been canceled.

&&

.Eastern Micronesia...
The main features that will be affecting Eastern Micronesia this week
will be two troughs and the area of trade-wind convection between.
Majuro will be stuck in the trade-wind convergence between the two
troughs all weekend and into next week. The most rain will be today,
then likely a gradual tapering. Weather will remain unsettled all
week though, with isolated showers and thunderstorms continuing.
Kosrae is expected to have scattered showers and isolated
thunderstorms through tonight, then isolated showers and
thunderstorms the rest of the weekend, except for Tuesday, when it
should clear up and be just partly cloudy with isolated showers.
Pohnpei will have the heaviest weather of all, being scattered
showers through Tuesday. For Wednesday, it will ease a little,
becoming mostly cloudy with isolated showers and thunderstorms.

Except for lightning near thunderstorms, no weather related hazards
are anticipated in Eastern Micronesia.

&&

.Western Micronesia...
The major feature affecting Western Micronesia is, of course, the 800
pound gorilla in the West Pac, Typhoon Surigae. Surigae is already
well west of Chuuk, so will have no effect there. Chuuk will have
more of the same benign weather as today through Monday. On Tuesday
and Wednesday, a few thunderstorms could start to impinge on the
Chuuk area. These are most likely related to the trough in Eastern
Micronesia. Although it`s much closer, Surigae is moving away from
Yap. So, scattered showers there today should become isolated by
tonight. A slight chance of thunderstorms will end by tonight...
assuming it hasn`t already ended. That leaves Koror... which is
expected to have scattered showers through tonight. Surigae is also
moving away from Koror, but it`s still substantially closer than
anywhere else. Therefore, Koror weather could stay unsettled through
Tuesday if any more of the outer rain bands of Surigae should hit.

For hazards, Chuuk should only need to worry about lightning near
thunderstorms on Tuesday and Wednesday. Yap has a high surf warning
right now, which is expected to diminish to an advisory tonight, and
seas are hazardous for small craft. Koror is in the hot seat with a
tropical storm warning, possible mudslides today, possible coastal
inundation, and a high surf warning. Surigae is moving away though,
and much of this will probably down by Sunday.

&&

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

$$

Marianas: Ziobro
Micronesia: Stanko