Area Forecast Discussion
Issued by NWS Tiyan, Guam

Current Version |  Previous Version |  Text Only |  Print | Product List |  Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
151
FXPQ50 PGUM 230813
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
613 PM ChST Thu May 23 2024

.Marianas Synopsis...
Skies this evening are mostly cloudy across Guam, and partly cloudy
across the CNMI, though showers are currently isolated across the
Marianas this evening. A weak trade-wind trough east of the
Marianas is moving westward and is associated with some increased
cloud cover and scattered showers. Latest altimetry shows combined
seas of 5 to 7 feet.

&&

.Discussion...
The MIMIC Total Precipitable Water (TPW) satellite product shows
drier air is starting to filter into the Marianas, with current
values across the Marianas currently around 2 to 2.3 inches, and
becoming 1.5 to 1.8 inches to the east and northeast, behind the
trade-wind trough currently just east of the Marianas. We do expect
enough moisture will be present for the trough to generate mostly
cloudy skies and low-end scattered showers across the Marianas later
tonight and into early Friday morning, but the potential for
thunderstorms is very low and contained to Guam`s southern waters.
The drier air will then spread across the Marianas through the day
Friday, decreasing showers and cloud cover through the afternoon.
Models then keep the Marianas in a fairly dry trade-wind pattern
through the weekend and middle of next week.

&&

.Marine...
Moderate winds and combined seas of 5 to 7 feet will slowly continue
to decrease and then stabilize this weekend, with winds becoming
gentle to moderate and seas around 4 to 6 feet. Some of the showers
and thunderstorms south of Guam the last couple of days have lifted
northward and clipped Guam`s southern waters this evening. A weak
trade-wind trough east of the Marianas will push in later tonight and
early Friday morning, extending scattered showers across the
Marianas waters, but the slight risk of thunderstorms will remain in
Guam`s southern waters tonight, and then diminishing Friday. There
is a moderate risk of rip currents along east and north facing reefs.
A low risk continues for south and west facing reefs. Surf is
expected to fall another 1 to 2 feet along north and east facing
reefs this weekend. This should cause the risk of rip currents to
become low along north facing reefs this weekend.

&&

.Fire weather...
The KBDI will likely continue to rise since so far today no rain has
been reported here at the weather office, and not expecting any
significant rainfall with any of the showers expected later tonight.
Moderate trade winds are still expected for another day, but then
will begin to subside this weekend and for much of next week,
perhaps easing some of the fire danger concerns, though atmospheric
moisture is expected to decrease, potentially allowing relative
humidity to decrease over the next few days.

&&

.Tropical systems...
The circulation, JTWC Invest 93W, is now southwest of Koror Palau,
near 6N133E, and is moving northwest. 93W is expected to continue in
this direction into the Philippine Sea, away from Palau. Satellite
imagery showed a weakening of overall convection today and models
indicating that the overall threat for strong, gusty showers has
decreased for Palau. The JTWC still rates 93W as a HIGH (TCFA) for
development, meaning TC development is likely within 24 hours, and
this is supported by models in the mid- to long-term as 93W continues
to move away from Palau. Convergent flow east of 93W will continue
to support showery weather far western Micronesia for the next couple
of days, but the overall threat for gusty winds and choppy seas is
decreasing.

&&

.Eastern Micronesia and Chuuk...
A broad trough in the far eastern portion of the region is at the
leading edge of a weak convergence zone. This pattern is expected
stretch westward across the region starting with Majuro this evening,
then Kosrae by Friday, Pohnpei by Friday night, and reaching Chuuk
sometime Saturday night. Scattered showers and spotty thunderstorms
are to be expected with this encroaching pattern. Then, model
guidance shows signs of the Inter-Tropical Convergence Zone (ITCZ)
strengthening early next week.

Benign marine conditions are expected over the next several days.
Moderate trade winds become gentle to moderate this weekend.
Combined seas are expected to be between 5 and 7 feet.

&&

.Western Micronesia for Palau and Yap...
The last update of the Special Weather Statement (SPS) was sent this
evening. Invest 93W is centered about 160 miles southwest of Palau
and is on track to continue northwest into Philippine Sea. Satellite
imagery showed a weakening of overall convection today and models
indicating that the overall threat for strong, gusty showers has
decreased for Palau, and even more so for Yap. Convergent flow
following the system will maintain showery weather, however,
conditions will gradually improve in the next day or so. A ridge
moves in Sun-Tue, to further weaken shower potentials, then a
transition to a trade-wind pattern ushers in another period of
scattered showers around the middle of next week.

The Small Craft Advisory for Palau was allowed to expire this
afternoon. Mariners should still exercise caution as occasional
fresh to strong gusts and choppy seas are still possible tonight.
Palau buoys indicate seas are 6 to 7 feet and altimetry data
similarly shows a range of 5 to 7 feet for the region. East to
southeast winds are moderate (occasional fresh gusts for Palau
tonight) then is expected to decrease to gentle to moderate by the
weekend as 93W gradually advances farther to the northwest towards
the Philippines.

&&

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

$$

Marianas: Schank
Micronesia: Cruz
Tropical: Cruz/Schank