256
FXPQ50 PGUM 261756
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
356 AM ChST Sat Jul 27 2024

.Marianas Update...
Showers and thunderstorms have diminished from south to north
overnight. Isolated showers for Guam and Rota to low-end scattered
for Tinian and Saipan. Passing disturbances will bring scattered
showers and isolated thunderstorms at times through the weekend.
Showers and the potential for thunderstorms look to increase next
week as a tropical disturbance drifts northeast out of central
Micronesia into the Marianas.

Combined seas of 4 to 6 feet through the weekend, combined of a
mixed easterly and westerly swell. Seas will decrease 1 to 2 feet
next week as the westerly swell emanating from distant Gaemi
diminishes. Winds will be light to gentle for the period. There will
be a moderate risk of rip currents along west facing reefs of the
Marianas through at least the weekend as a result of the westerly
swell.

&&

.Tropical Systems Update...
Invest 95W is rated medium for tropical development, meaning
development into a tropical cyclone is likely, but beyond 24 hours.
Satellite and scatterometry reveal a broad circulation with a center
located near 6.9N134.5E, Just to the south of Koror, Palau.
Convection is still unorganized around 95W. Overall, models show a
northwest track with tropical cyclone development more likely after
it passes northwest of Yap and Palau.

&&

.Eastern Micronesia and Chuuk Update...
The ITCZ with trade-wind troughs are keeping the entire region wet
for the weekend. The major difference tonight has been the adding of
Chuuk to the weather regime. Both Majuro and Kosrae are on the
leading edge of two troughs. Pohnpei is currently under a weak
ridge, however this is expected to change as the day progress. Chuuk
on the other hand is at the far western tip of the ITCZ, the
tradewinds are being pushed southward over Weno, and to the east a
bit is the that was over Pohnpei yesterday.

Winds are expected to be gentle to moderate with the strongest winds
near the showers. Altimetry shows combined seas near Chuuk at 2 to 4
feet, and seas near Majuro at 4 to 6 feet.

&&

.Western Micronesia for Yap and Palau Update...
A Small Craft Advisory remain in effect for Palau through this
afternoon. The Small Craft Advisory was cancelled for Yap.

Invest 95W remain the dominate feature for the region. Satellite
imagery has observed that the showers associated with 95W are mostly
to the north northwest side of this feature. Scattered showers remain
in the forecast for both Yap and Palau, however the winds near Yap
have diminished overnight. Showers are on the cusp of being numerous
for Palau and may needed to be updated later today if this system
strengthens.

Combined seas remain around 2 to 4 feet. Winds are expected top be
moderate to fresh near Palau, and gentle to moderate near Yap. Seas
will be rougher near the storms associated with 95W.

&&

.Prev discussion... /issued 616 PM ChST Fri Jul 26 2024/

Marianas Synopsis...
Satellite and radar (yes, I meant to say radar) observations show
scattered showers across the Marianas, especially over the southern
portions of Guam and its southern coastal waters. Altimetry and buoy
data show combined seas between 3 and 5 feet.

Discussion...
Not much change was made to the forecast with tonight through
Saturday night still looking somewhat active across the Marianas.
Could see a period tonight or Saturday where coverage increases over
portions of the Marianas, but confidence was too low to reintroduce
numerous due to the mesoscale models down trending some. As we get
into Sunday, there will be a lull from the shower and thunderstorm
activity as the Tropical Upper Tropospheric Trough shifts away from
the region and the trade-wind trough it`s interacting with shifts
westward out of the Marianas. This lull appears short lived as by
Wednesday we will be looking towards our next surface trough that
will be lifting out of eastern Micronesia, which will bring
scattered showers to the Marianas.

Marine...
The westerly swell that was produced by former Typhoon Gaemi will
start to subside Sunday and will eventually be replaced by an east
well Monday night into Tuesday. Trade-winds look to remain gentle
through much of the week next week, so surf may fall to low for all
reefs with some potential of a moderate risk for rip currents for
east facing reefs.

Tropical systems...
Invest 95W is now rated medium for tropical development, meaning
development into a tropical cyclone is likely, but beyond 24 hours.
Satellite reveals a broad circulation with a center located near
7N134E, on the outskirts of Palau`s southwestern waters. Convection
is still unorganized around 95W, with the heaviest showers and
thunderstorms currently developing in the western sector. Maximum
winds are estimated 15 to 23 kt and OceanSat-3 scatterometry data
depicts strongest winds are with north to northwestern winds
wrapping around 95W. Overall, models show a northwest track with
tropical cyclone development more likely after it passes northwest of
Yap and Palau.

Eastern Micronesia...
A sharp and strong surface trough is moving west into the Marshall
Islands this evening with numerous showers and a few thunderstorms,
although mainly south of 10N. Its basically riding along the ITCZ
that has shifted slightly southward. Also a surface trough moving
from Kosrae toward Pohnpei is causing patchy areas of showers and
very isolated thunderstorms over Pohnpei and Kosrae States. The sharp
trough will continue westward over the next few days with numerous
showers at times this weekend for both Kosrae and Pohnpei. Behind the
sharp trough, weather conditions should gradually improve form east
to west, starting at Majuro by Monday.

Surging surface winds along and behind the sharp trough will cause
combined seas of 5 to 7 feet for the Majuro area, with locally bigger
seas near showers and gusty winds. Otherwise, combined seas of 4 to
5 feet are expected for Kosrae and Pohnpei. Winds and seas could
decrease again next week as the ITCZ drifts back north.

Western Micronesia...
Invest 95W was upgraded to medium around noontime today, meaning
that tropical cyclone development is likely, but beyond 24 hours. 95W
is embedded within the monsoon trough, near 7N134E, placing the
center on the outskirts of Palau`s southwestern waters, then the
monsoon trough extends east-northeast over Ulithi and ending
northwest of Chuuk. Moderate to deep convection around 95W appears
less organized than it did earlier this morning, but model guidance
indicates further development as it treks northwest away from Palau.
Due to the proximity of 95W, strong gusts with heavier showers are
still expected, Hi-Res models still indicate pockets of 24-28 kt
winds, mainly around Palau and to a lesser extent, Yap. Behind 95W
and its trailing monsoon tail, a ridge of high pressure will aim to
suppress showers for far western Micronesia in the first half of
next week. Satellite shows fairer weather over Chuuk this afternoon,
but conditions are expected to deteriorate over the weekend due to a
weak disturbance developing in central Micronesia.

Altimetry and buoy data reveals 2 to 4 foot seas near Palau and wave
models indicate seas 3 to 5 elsewhere. A Small Craft Advisory is in
effect through Saturday afternoon for Palau and Yap. Gusty winds
increasing wind waves are expected with wave guidance indicating
seas peaking near 5 feet for Palau overnight. Northwest swell from
Tropical Storm Gaemi is abating and small northeast and southeast
swell is expected this upcoming week.

&&

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

&&

$$

Marianas: Slagle
Micronesia: Bowsher