394
FXPQ50 PGUM 120810
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
610 PM ChST Wed Jun 12 2024

.Marianas Synopsis...
Satellite imagery shows a few showers exiting the islands following
the morning`s flare up of heavy showers and thunderstorms. Thinning
cirrus is still present over the Marianas while additional showers
and thunderstorms are seen well southeast of Guam. Ritidian Buoy and
altimetry data show seas of 4 to 5 feet around the region. Seas are
about a foot higher well east of the Marianas.

&&

.Discussion...
Latest forecast largely follows the reasoning of the past 12-24
hours, that convection within this very moist airmass will be more
diurnally-driven with periods of quiet separated by developing
showers and thunderstorms. Have indicated more unsettled weather
later tonight for Guam and Rota in anticipation of the convection
well to the southeast moving this way. Models suggest showers will
increase for all of the Marianas Thursday before subsiding again
Thursday night and Friday.

An upper-level low between the Marianas and Wake Island is slowly
heading west toward the Marianas. As it moves into and to the west of
the islands, upper-level winds should become more supportive for a
northward spread of showers and thunderstorms. Friday night and
Saturday look to be the best time frame for the unstable weather. By
Saturday night and Sunday, conditions should improve with gentle to
moderate trade winds dominating into early next week.

&&

.Marine...
While no marine hazards are in effect or anticipated, showers and
thunderstorms expected to move into Guam and Rota waters overnight
could bring some brief gusts of 20-25 kt. Satellite imagery this
afternoon shows gusty outflow boundaries running ahead of the
showers and thunderstorms, moving at around 25 kt. These gusts would
be short-lived but still add some chop to local waters in passing.

Made a few adjustments to reduce combined seas the next couple of
days, keeping seas to between 3 and 5 feet. The anticipated uptick in
seas is still expected heading into the weekend, with trade swell
building and seas rising 1-2 feet to between 5 and 7 feet. A moderate
risk of rip currents along east reefs could then spread to north
facing reefs over the weekend.

&&

.Eastern Micronesia...
Visible satellite during the day showed two distinct trade-wind
troughs impacting the region. The first is just east of Majuro with
multiple pockets of deep convection south and east of Majuro along
the trough axis. The second trough is producing pockets of deep
convection mainly south of Kosrae during the day. Latest model
analysis shows the ITCZ (Inter-Tropical Convergence Zone) currently
located on satellite east of Majuro building westward through Kosrae
and south of Pohnpei through Saturday. Scattered showers and isolated
thunderstorms will be mainly along and north of the ITCZ in the area
of convergence. Model trends over the last several days continue
showing the ITCZ fragmenting into individual trade-wind troughs
around the beginning of next week before transitioning into a trade-
wind pattern through the middle of next week bringing periods of
showers to the region.

Light to gentle trades and benign seas conditions are expected to
persist at Kosrae and Pohnpei through early next week. For Majuro,
gentle to moderate trades and benign conditions are expected through
early next week. Altimetry passes during the day show combined seas
between 3 to 5 feet through the Marshalls with combined seas of 4 to
6 feet well closer to the International Date Line.

&&

.Western Micronesia...
A vigorous trade-wind trough located approximately 3N142E to 8N142E
has continued to generate pockets of moderate to deep convection
along and ahead of the trough axis due to convergence along the
trough. Model analysis during the day shows the trough will continue
to push over Yap and Palau through at least Saturday bringing
scattered showers and isolated showers to both locations. For the
latter part of the weekend through the middle of next week, a series
of trade-wind troughs will move over Yap and Palau from eastern
Micronesia bringing in periods of showers. For Chuuk, a weak trade-
wind trough will bring scattered showers on Thursday. Models then
show multiple troughs breaking off the ITCZ and traversing Chuuk
State bringing bouts of scattered showers and isolated thunderstorms
due to convergence along the troughs. For the latter part of the
weekend through the middle of next week, troughs will traverse the
Chuuk and bring periods of showers as the ITCZ fragments and
dissolves into a trade-wind pattern.

Light to gentle trades and benign seas conditions can be expected at
Chuuk, Yap, and Palau through early next week. Altimetry passes
during the day show combined seas between 3 and 4 feet.

&&

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

$$

Marianas: Aydlett
Micronesia: Kelly