Drought in Guam, February 1 to 28, 2022

Area Forecast Discussion
National Weather Service Tiyan GU
1034 PM ChST Mon Jan 31 2022

.Marianas Synopsis...
The latest visible satellite imagery continues to show increasing
high cloud cover, as winds aloft are from the southeast becoming
southerly. The latest doppler radar is void of any significant
showers, with just a few light returns to our southeast and mid
level returns (clouds) observed east of Rota. The latest Ipan
observations show seas just over 5 feet with a water temperature
of 83 degrees.

&&

.Discussion...
The story remains the same for the weather for Tuesday through the
weekend. In short, a shear line just to the south of Guam remains
in place, with a few very light showers seen on Doppler radar to
our southeast. However, winds aloft have become southeasterly, and
they'll become more southerly over the next 24 hours, allowing
high-level (above 30,000 feet) cloud cover to increase. Otherwise,
we're keeping our eyes on a shear line approaching from the north
and northwest. This feature bisects the CNMI and Iwo To, and is
making fairly good progress speed wise as it continues pushing
towards the Marianas/CNMI. This should reach Pagan by late
Tuesday night or Wednesday, Tinian and Saipan late Wednesday
night, and to Guam and Rota by Thursday. Along it and in its wake
look for winds to become breezy with gusts to 30 knots (~35 mph)
possible during the afternoon hours, especially near any heavier
shower.

Speaking of these showers, have continued the "split grid
approach" to show the timing/earlier arrival up north, reaching
Guam later. We'd prefer to see a deeper moisture profile for
higher shower coverage, but given the moisture topping out near
700 mb (~10,000 feet), will keep maximum POPs (Probability of
Precipitation) and 50 percent, with only modest omega values in
that layer adding to this decision. This shear line and increased
cloud cover/shower potential could hang around for Friday evening
into Saturday, so we'll see what later model runs show for any
potential forecast adjustments.

&&

Marine/Surf...
All eyes are to our north and northwest, or they will be, in the
next 48 hours. This is due to a shear line dropping south into our
region, with this feature having covered a decent amount of space
today as it's been moving close to 25 mph. As it moves into the
Marianas, winds will be fresh to strong at times, with gusts to 30
knots likely. Seas will also build to 10 feet, and a small craft
advisory will need to be hoisted in the next 24 to 36 hours.
These seas will also cause high rip risk and high surf concerns,
with these headlines also probably issued as a "bundle" by this
time tomorrow (Tuesday afternoon/evening).

&&

.Eastern Micronesia...
Moderate to fresh trade winds prevail in eastern Micronesia, bringing
partly cloudy skies and isolated showers to much of the region. Only
minor changes were made to the forecast, mainly to the sea heights
towards the end of the week. A trade-wind surge is developing east of
the dateline, which will continue on west and pass over Majuro on
Tuesday night, followed by Kosrae on Thursday and lift off to Pohnpei
on Saturday. The most intense development of this surge is expected
over Kosrae and Majuro on Saturday, and as such, locally heavy
showers are possible towards the end of the weekend. Time heights
continue to indicate dry mid-levels until the arrival of the surge,
which will keep showers fairly infrequent and lightning potential to
a minimum.

Pohnpei, Kosrae and Majuro will see their seas rise further due to
multiple incoming north swells from systems well east of Japan. The
ECMWF wave model continues to be the king model for north swell
influence in the region, being the one to match the closest to the
latest altimetry passes with an average deviation just under 1 foot.
GFS Wave, in the mean time, continues to under-perform with incoming
swell heights and combined sea heights between 1 and 2 feet under,
which may be attributed to how the parameters over-estimate the
shielding caused by a variety of atolls north of the main islands.
Conditions are no longer hazardous to small craft at Pohnpei and
Kosrae tonight, but may hasten and become hazardous once again as
elevated winds and seas return Thursday due to a building high
pressure system well northeast of the Marianas and squeezing the
trades even further, which will come closest in proximity to the
region sometime midweek. Majuro may see hazardous conditions to small
craft starting Friday, as another trade-wind surge picks up again.

&&

.Western Micronesia...
Moderate to fresh trade winds prevail in western Micronesia, as a
near-equatorial trough and a broad trade-wind trough continue to
bring saturated and unstable conditions across much of the region.
The GFS and ECMWF indicate that the bulk of the convection from these
features interacting will stay just south of Palau as it makes its
way towards the Philippines, but the proximity to Palau gives way for
scattered bursts throughout Tuesday and Wednesday, making locally
heavy showers and occasionally strong gusts possible for that period.
Starting Thursday, Palau should see showers and thunderstorm
potential diminishing through at least the end of the week. Yap will
be spared the bulk of the thunderstorms and showers, with just a
slight uptick in showers possible midweek.

Just like in eastern Micronesia, ECMWF wave has initialized the best
with the most up-to-date altimetry passes. Seas will start to
increase from between 6 and 8 feet to between 8 and 10 feet on
Thursday for Palau, and Friday for Yap and Chuuk. Sea conditions may
become hazardous to small craft due to elevated winds on Tuesday for
Palau, Tuesday night for Yap, and Friday for Chuuk.

&&

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

Marianas: Doll
Micronesia: Pavliukoit