NWS Guam wrote its last area forecast discussion before the first event at Mar 8, 7:56 PM UTC, 8 hours 4 minutes earlier.
Area forecast discussion, Mar 8, 7:56 PM UTC, 8 hours 4 minutes before
Area Forecast Discussion
National Weather Service Tiyan GU
556 AM ChST Sat Mar 9 2024
.Marianas Synopsis...
Partly cloudy skies with isolated showers and gentle to moderate
trade winds prevail across the Marianas this morning. Tanapag buoy
shows seas between 3 and 4 feet while altimetry shows 5 to 6 feet.
&&
.Discussion...
No major changes from the previous forecast. A weak trade-wind
trough approaching the Marianas along with a surge in the trades will
result in scattered showers across the islands tonight into Sunday
afternoon. Rainfall amounts, however, won't be very impressive.
Models continue to move a weak shear line into the region Monday,
with building trade winds. Breezy conditions are possible as early as
Sunday night.
&&
.Marine...
Gentle to moderate trade winds and combined seas of 4 to 6 feet are
expected to continue today. Winds and seas look to begin to build
tonight into Sunday due to the approach of a trade-wind trough and a
trade surge pushing into the Marianas. These features will also
bring low-end scattered showers to the waters tonight into Sunday
afternoon. Seas and winds will continue to increase Monday as fresh
to strong trade winds push into the waters and a weak shear line
moves in from the north. Both seas and winds are expected to increase
sufficiently to become hazardous for small craft operations.
Therefore, a Small Craft Advisory is possible as early as Monday
morning, continuing through at least the middle of next week. This
increased trade swell is also expected to bring a high risk of rip
currents to east facing reefs. A strong low pressure system east of
Japan is also expected to produce a modest north-northwest swell
beginning Monday. This swell is expected to increase the rip current
risk to moderate along west and north facing reefs.
&&
.Fire weather...
Dry conditions prevail across Guam. Only 0.01 inch of rain fell
yesterday, allowing the KBDI to increase to 676, which is still in
the high category. A trade-wind trough looks to move through the area
tonight into Sunday, bringing an increased chance of showers.
However, rainfall with this trough looks to remain unimpressive. The
good thing is that winds look to be a bit lower today than they were
yesterday, so a Fire Weather Watch will not be issued. If winds pick
up more than expected, this could change. The bad news is that winds
look to begin to increase Sunday into Sunday night, with breezy
conditions expected Sunday night into through at least Tuesday.
Combined with strong winds, the KBDI will probably reach into the
very high category. Combined with low RHs expected on Monday, a Fire
Weather Watch is likely beginning Monday into at least Tuesday
afternoon, possibly through the middle of next week.
&&
.Eastern Micronesia...
Latest satellite imagery shows fairly dry weather over Pohnpei and
Majuro this morning, while speed convergence, created by the
stronger winds of the trade-wind surges flowing into the weaker winds
near the equator, are producing scattered to numerous showers just
south of Kosrae. This speed convergence is also generating low to
mid clouds that extend back to the Date Line, passing to the south
of Majuro. Scatterometer shows winds are around 20 knots at Pohnpei
and then increasing to 20 to 25 kt when looking eastward to Kosrae
and especially Majuro. Altimetry shows seas of 10 to 13 ft around
Majuro and then decreasing to 8 to 10 feet towards Kosrae and
Pohnpei.
The leading edge of a weaker trade-wind surge is just east of Pohnpei
and extends into Kosrae, while the western edge of a stronger trade-
wind surge, that extends from Hawaii, is pushing into the Marshall
Islands. This trade-wind surge pattern will continue as the stronger
trade-wind surge spreads westward. Small Craft Advisories remain in
effect at Pohnpei, Kosrae, and Majuro through at least Wednesday
afternoon as the winds and seas/swell associated with the trade-wind
surge will keep conditions hazardous to small craft. The swell
generated by the trade-wind surge will also continue to create
hazardous surf along east facing reefs of Kosrae and north and east
facing reefs of Majuro, so the High Surf Advisories have also been
extended through Wednesday afternoon. A Coastal Flood Statement also
remains in effect for Majuro through Wednesday afternoon as the high
surf with he King Tide cycle, that peaks around Sunday through
Tuesday, is expected to cause minor flooding during high tide. The
Pacioos Wave Run-Up Forecast shows the potential for moderate coastal
inundation, especially if surf is higher than currently forecasted,
so be on the lookout for flooding near high tide. The trade-wind
surge is expected to weaken after Wednesday, but depending on how
quickly this happens, advisories may need to be extended beyond
Wednesday.
Overall, a fairly dry pattern continues north of 5N through the rest
of the weekend, though convergence along the southern edge of the
trade-wind surge, will continue to generate showers to the south of
Kosrae. Starting around Tuesday, the GFS and ECMWF indicate some
kind of disturbance trying to develop to the south of Chuuk, and then
slowly lifting north. This is around the same time the Madden-Julian
Oscillation (MJO) starts to push back into the Western Pacific from
the Maritime Continent. This would help to lift the area of
convergence northward and potentially bring some heavier rainfall to
Kosrae and then Pohnpei late next week, so this is something to watch
and see if anything starts to develop over the next few days.
&&
.Western Micronesia...
Satellite imagery continues to show a fairly quiet and dry pattern
across western Micronesia. Most of the heaviest convection remains
along or south of the equator, especially well south of Chuuk State
this morning, while some weak trade-wind troughs are producing some
spotty to scattered showers north of 10N, mainly east and west of the
Marianas. Shower activity is expected to remain close to the
equator, well south of the forecast points for the next several days.
However, the GFS and ECMWF indicate some kind of disturbance trying
to develop to the south of Chuuk next week, and then lifting north.
This is around the same time the Madden-Julian Oscillation (MJO)
starts to push back into the Western Pacific from the Maritime
Continent. For now, models do not have showers reaching up to Chuuk
Lagoon until about Friday, but this is something to watch to see if
something starts to develop like the models are predicting. Around
Monday, another high pressure system moves off the coast of Japan,
which is expected to bring stronger winds for Yap and possibly Palau
as it helps to strengthen the trade winds and pushes a shear line or
shear line fragment towards the Marianas and the Phillipines.
Altimetry data shows combined seas are 4 to 6 feet near Yap and
Palau, and up to 8 feet at Chuuk. Seas are then expected to build
over the next few days with the building trade winds/swell extending
from eastern Micronesia and shear line descending into far western
Micronesia, along with some northerly swell generated by northerly
winds near Japan. This should build combined seas to around 8 to 9 ft
for Yap and Palau, and possibly up to 10 feet around Chuuk starting
around Monday, potentially requiring a Small Craft Advisory for
Chuuk. With increasing north and east swells, surf may become
hazardous next week as well.
&&
.GUM WATCHES/WARNINGS/ADVISORIES...
GU...None.
MP...None.
Marianas Waters...None.
&&
Marianas: Kleeschulte
Micronesia: Schank