367
FXPQ50 PGUM 270643
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
443 PM ChST Thu Jun 27 2024

.Marianas Synopsis...
Partly cloudy skies with isolated showers and gentle to moderate
trade winds prevail across the Marianas this afternoon. Guam is
seeing occasional strong gusts. Ritidian buoy shows seas near 5 feet
while altimetry shows seas in the 4 to 6 foot range.

&&

.Discussion...
A dry trade-wind pattern remains in place across the Marianas this
afternoon. Over the weekend, a trade-wind trough, currently seen
near 170E, is expected to move through the Marianas, with a second
trough seen a little farther south not far behind the first trough.
As the first trough moves through the Marianas, upper-level
divergence, associated with a TUTT (Tropical Upper-Tropospheric
Trough) cell expected to be to the northwest of the Marianas, will
create a marginally favorable environment for thunderstorms to
develop across the Marianas. Therefore, have a slight chance of
thunderstorms in the forecast for Saturday and Saturday night. By
Sunday, the second trough will arrive, farther south, affecting Guam
and possibly Rota. At the same time, the TUTT cell is expected to
move out, with an upper-level ridge replacing it, putting the
Marianas under a band of convergence aloft. This will inhibit
thunderstorm development. Based on this, expect low-end scattered
showers across Guam and Rota Sunday and Sunday night with no
thunderstorms expected.

Latest model guidance continues to show the development of a west-
east oriented trough developing across Micronesia, west of Pohnpei,
with several weak circulations popping up here and there over most of
next week. It currently looks likely that the bulk of convection
will remain south of the Marianas. However, due to the vicinity of
another TUTT cell possibly producing weak upper-level divergence over
the Marianas for several days, maintained mostly cloudy skies with a
slight chance of thunderstorms for most of next week.

&&

.Marine...
Combined seas of 4 to 6 feet will continue into the weekend, then
slowly subside to between 3 and 5 feet Sunday. The seas will be
mainly comprised of a moderate trade-wind swell. This swell will
maintain surf high enough to produce a moderate risk of rip currents
along east facing reefs through at least the middle of next week. The
rip current risk will be low along all other reefs. Gentle to
moderate trade winds are expected through the beginning of next week.

&&

.Eastern Micronesia...
A pair of westward-moving surface troughs are focusing showers near
Pohnpei and atop the western chain of the Marshalls. A cluster of
thunderstorms has been evident south of Kwajalein through the
afternoon, but, for the RMI, convection is slowly clearing out as it
treks west. Latest CIMSS MIMIC TPW shows a wide band of increased
moisture with PWATs well over 2in across Pohnpei and Kosrae. A drier
air mass is moving into the Marshalls for the short term, but more
moisture will eventually move into the region. For most of the
region, the forecast is generally on the wetter side, reflecting the
increased regional moisture and the anticipation of a more active
ITCZ pattern taking shape over the weekend. Early in the weekend,
showers are expected to stay between 3-4N and 8N, then gradually lift
northward by early next week, perhaps up to 12N.

Seas will be fairly benign with no hazards anticipated other than
localized effects from areas of heavier showers or thunderstorms.
Winds will be mostly moderate, occasionally fresh with seas staying
between 3 and 5 feet, maybe up to 6 or 7 feet just east of the
Marshalls. Wave model data shows a dominant easterly swell though
Pohnpei and Kosrae will see some southeasterly swell from
southeasterly trades across the South Pacific.

&&

.Western Micronesia...
A weak trade-wind convergence pattern is maintaining scattered
showers and a few thunderstorms across the area, mostly near Yap and
farther south of Chuuk. For Palau, conditions have quieted with only
a few showers. A moderate trade-wind pattern will dominate the region
the next couple of days before winds really begin to weaken over the
weekend. Have largely maintained scattered showers (30-50 POPs) for
much of the forecast for all 3 locations based on the wetter pattern
models depict from weakly convergent trades or passing trade-wind
troughs. Subsequent forecast issuances will have the opportunity to
better identify short-term drier spells that are obscured more than
a day in advance. Heading into next week, a weak surface wind pattern
may at times allow some weak circulations to briefly appear but
models show nothing of significance taking root beyond a weak flow
pattern.

Similar to eastern Micronesia, seas will be subdued, generally
between 3 and 5 ft with seas up to 6 ft north of Yap and Chuuk.
Currently, no marine hazards are anticipated in the next few days.

&&

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

$$

Marianas: Kleeschulte
Micronesia: Aydlett