Drought in Guam, April 1 to 27, 2023

Area Forecast Discussion
National Weather Service Tiyan GU
709 PM ChST Fri Mar 31 2023

.Marianas Synopsis...
Gentle to moderate trade winds, partly cloudy skies and isolated
showers prevail. Ritidian and Ipan buoys are both measuring seas of
5 feet, composed of ENE trade swell and wind waves.

&&

.Discussion...
Little change to the previous forecast. Shower and thunderstorm
chances are expected to increase Monday as deep-layer moisture ramps
up and winds flip out of the south. The main belt of showers look to
focus east of the Marianas, as a lobe of vorticity currently south
of Chuuk Lagoon, sweeps northward and interacts with a favorable
upper-level pattern and convergent southerly flow. Gusty southerly
winds are likely to develop in this hefty band of showers and
thunderstorms east of the Marianas. Guidance still keeps this gusty
regime well east of the islands at this time. The western extent of
this shower complex should brush the Marianas during the Monday to
Tuesday timeframe. Winds turn around to the west and northwest
through the day on Tuesday as a frontal system treks by to the north.
A definitive, drier northerly flow filters in for Wednesday, with
trades returning late in the week.

&&

.Marine...
A benign marine pattern stretches through early next week with gentle
to moderate trades and seas of 5 feet or less. Trades turn out of the
south Monday with bands of showers and thunderstorms. The eastern
waters would see the best chance of gusty southerly winds, but
guidance still keeps this activity outside the eastern coastal
waters. A frontal system, currently draped over the Ryukyu Islands
of Japan, is forecast to intensify to our north the next few days.
While models have bounced around a bit with timing and storm
evolution, there is decent support for a sizable northerly swell to
build early Wednesday across the Marianas. Seas and surf may reach
hazardous levels due to northerly swell and wind waves.

&&

.Eastern Micronesia...
An active Inter-Tropical Convergence Zone (ITCZ) is stretching from
near Chuuk to east of the date line. Several weak troughs are also
propagating across the ITCZ through the region. The ITCZ will
fluctuate north and south through the weekend and will be the major
weather player, with scattered to at times numerous showers and
isolated thunderstorms. In addition, a near-equatorial trough (NET)
with an embedded circulation is currently south and west of Chuuk.
This will enhance convergence in the area but the strongest (and
heaviest precip) looks to remain just west of Chuuk. If it meanders
east, heavy rainfall could occur of the lagoon. The ITCZ looks to
weaken and fragment next week as trade winds strengthen and push the
convergence a bit south of the main islands. Showers look to become
more isolated to low end scattered.

Gentle to moderate trade winds for Majuro. For Chuuk, Pohnpei and
Kosrae, light to gentle winds expected. Winds increase next week for
Majuro, becoming moderate to fresh, and for Kosrae, becoming mainly
moderate. Light to gentle winds will continue for Chuuk and Pohnpei.
Combined seas are expected to continue to subside this weekend,
becoming 4 to 6 feet for Majuro and 3 to 4 feet elsewhere. For mid to
late next week, a trade swell, followed by a sizable northerly
swell, will bring increasing seas. Wave heights expected to rise 6 to
8 feet, possibly higher.

&&

.Western Micronesia...
Mainly isolated showers for Yap and Palau for the weekend into early
next week. Weak trade convergence near Yap, along with surface
troughing extending northwest from a circulation across eastern Yap
state, could bring low end scattered showers and isolated
thunderstorms as it pivots south across the region through the
weekend. Some island effect convection possible as well for Palau
with the light winds expected. Model guidance shows a stronger
trough extending from a low pressure system passing north of the
Marianas, pushing south into Yap and Palau. Depending on timing and
location of this feature, could see increased showers for Yap and
Palau. Currently, the forecast has scattered showers for both
locations around Wednesday.

Marine conditions look to remain fairly benign over the coming days,
with light to gentle winds and combined seas of 2 to 4 feet. Winds
increase with the trough passage, becoming gentle for Palau and
gentle to moderate for Yap by mid week. In addition, a sizable
northerly swell is expected to push into the region, with seas
currently forecast to become 6 to 9 feet for Palau coastal waters and
7 to 10 feet for Yap coastal waters mid to late next week.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...

GU...None.
MP...None.
Marianas Waters...None.

&&

Marianas: Bukunt
Micronesia: Slagle