Drought in Guam, February 1 to 28, 2021

Area Forecast Discussion
National Weather Service Tiyan GU
714 PM ChST Sun Jan 31 2021

.Marianas Synopsis...
Shear line just north of the Marianas is bringing fresh to strong
winds for northern Marianas with combined seas just above small
craft criteria of 10 feet. Tanapag and Ritidian buoys are reporting
just over 10 feet. Radar shows some lines of low level cumulus
passing through bringing some light showers.

&&

.Discussion...
Not much change to the forecast. Adjusted the timing of some minor
weather passing through, mainly scattered showers. No mention of
thunderstorms for the forecast period. Tuesday and Wednesday looks
to be the most notable weather for the week, as a round of low level
clouds pass through, with GFS showing it to be very dry at the mid
levels. Also, with some upper level diffluence near the area, we may
see more cloud coverage and higher clouds.

&&

.Marine...
Issued small craft for Guam and Rota as both Tanapag and Ritidian
buoys reported combined seas of over 10 feet. Winds should increase a
little bit by Tuesday so may need to include winds of 25 kts into
the advisory. Saipan and Ritidian remain in a small craft advisory
for winds and seas until Wednesday evening, but there's a good
chance that it will have to be extended.

Updated the surf advisory for north facing reefs to remain in effect
until Tuesday evening. Models show significant decrease of northerly
swells on Tuesday but swells from the northeast start ramping up, so
wanted to be covered as the surf advisory transitions from north
facing reefs to east facing.

&&

.Eastern Micronesia...
An area of trade-wind convergence is producing an area of patchy
clouds and showers over the eastern half of Micronesia. Satellite
imagery shows a patch of showers near Majuro. Models indicate that
this area will produce scattered showers over Majuro for at least
part of tonight. Models show that this area will push south of the
three forecast locations and only isolated showers are expected at
Pohnpei through Friday and Monday through Friday at Majuro. A surface
trough will move across the Date Line by midweek and this will push
the convergence area slightly northward. This movement northward will
be slight, but will be enough to bring scattered showers and a slight
chance of thunderstorms to Kosrae Wednesday through Thursday.

High pressure to the north will be strong and persistent enough to
help elevate winds across the eastern half of Micronesia. This will
keep winds between 15 to 25 knots at all locations through Friday.
Winds this high are hazardous to small craft. Seas will also remain
at or above 10 feet at Pohnpei and Majuro. Seas at Kosrae will be
below 10 feet through Monday night but should rise at or above this
level by Tuesday. Seas at or above 10 feet are hazardous to small
craft.

The long-period north swell has decreased and surf has fallen below
hazardous on north facing reefs of Pohnpei and Kosrae. Trade-wind
swell has increased and will cause surf to become hazardous along
east facing reefs of Kosrae. These conditions will persist through
the week. Another northerly swell will build across Pohnpei and
Kosrae by Tuesday night with another round of hazardous surf possible
at that time.

&&

.Western Micronesia...
Activity remains distant from the three forecast locations and only
isolated showers are expected at them tonight and Monday. A
trade-wind disturbance will bring scattered showers with a slight
chance of thunderstorms to Palau Monday night. Low-level convergence
will generate scattered showers and isolated thunderstorms at the
same location Wednesday. A surface trough will bring scattered
showers to Chuuk Tuesday night and Wednesday. The Precipitable Water
Index and the Galvez-Davison Index remain relatively low at that time
so do not expect thunderstorms with the scattered showers at Chuuk.
The activity will not get close enough to Yap so only isolated
showers are expected there through the forecast. There may be enough
instability Friday at Yap to generate a few thunderstorms.

Seas will be high enough to be hazardous to small craft at Palau and
Yap through Monday night. High pressure building to the north will
help increase winds over Yap Thursday with wind of 15 to 25 knots
expected on that day increasing to 20 to 25 knots Friday. Chuuk will
also see winds increase to between 15 to 25 knots and seas to 10 feet
or more Monday, which is hazardous to small craft.

Northeast swell will continue to produce hazardous surf along north
facing reefs of Palau and Yap through the first half of next week.
The northeast swell has subsided at Chuuk this afternoon but may rise
again later this week.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...High Rip Current Risk through Wednesday afternoon for GUZ001>004.

     High Surf Advisory until 6 PM ChST Wednesday for GUZ001>004.

Marianas Waters...Small Craft Advisory until 6 PM ChST Wednesday for PMZ153-154.

&&

Marianas: Hong
Micronesia: Ziobro