Area Forecast Discussion
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FXPQ60 PGUM 170946 CCA
AFDPQ

Area Forecast Discussion...Corrected
National Weather Service Tiyan GU
650 PM ChST Sun Dec 17 2017

Corrected positions in Tropical Systems section

.Marianas Synopsis...
Partly cloudy skies, isolated showers and moderate to fresh winds
prevail across the region. Latest buoy data shows seas between 6 and
8 feet.

&&

.Discussion...
Very few changes were made to the latest forecast. Model guidance
shows winds a bit weaker over the next couple of days, although
moderate to fresh winds tonight are still expected to increase fresh
to strong by Wednesday. A fairly dry pattern is now over the Marianas
and is expected to continue through the week. The only caveat to
this is Invest 97W. Depending on what actually occurs with this
system, it could bring a wetter pattern to the Marianas if it drifts
a little further northward. This system will continue to be monitored
closely over the next few days. See the Tropical Systems section for
more discussion concerning Invest 97W.

&&

.Marine...
Seas are currently between 6 and 8 feet across the Marianas coastal
waters this afternoon. Seas are expected to slowly build over the
next couple of days, with seas possibly reaching Small Craft Advisory
levels around midweek. Winds are also expected to increase, becoming
fresh to strong Wednesday as well. Based on the expected conditions,
a Small Craft Advisory may be needed by midweek for both winds and
seas and a high risk of rip currents on east facing reefs is
possible Tuesday.

&&

.Tropical Systems...
The models continue to struggle with Invest 97W. Invest 97W remains
a weak system to the south of Chuuk and Pohnpei. Latest ASCAT and
SCATSAT data show that 97W is an elongated system with 2 weak
centers, one near 4N149E, the other near 7N142E. Latest model
guidance now shows the system drifting westward, with slow
development over the next few days, before moving out to the
northwest over Palau. The previous model run showed no development
at all, with the system dissipating within the next couple days.
Based on model run to run inconsistencies, confidence remains very
low on this system.

&&

.Eastern Micronesia...
A trade-wind surge has been creating a convergence band with
scattered showers and isolated thunderstorms in Eastern Micronesia.
As the surge is pushing farther in, these showers are now moving to
the south of Pohnpei, Kosrae and Majuro. This will mean relatively
dry weather the next several days, with the main threat being
hazardous surf. This moderate to fresh trade-wind fetch extends
almost all the way to Hawaii. Therefore, it has plenty of fetch
length to work with, and it has persisted for several days. This will
result in near small craft advisory seas and hazardous surf on east
facing reefs. Since this fetch changes little in the coming days, the
waves could last quite some time, so worded the advisory through at
least Wednesday. Pohnpei will have to be watched to see if they might
hit high surf advisory criteria later.

&&

.Western Micronesia...
Right now Chuuk is being affected by the convergence band at the
leading edge of the trade-wind surge. After these showers push
through, the weather at Chuuk will be much like that in Eastern
Micronesia. Like Pohnpei, they will have to be watched to see if they
might hit high surf advisory criteria later. The forecast for Yap and
Palau is the dramatic one. Model to model consistency has been fairly
good on invest area 97W, but as mentioned above, run to run
consistency has been poor. This is leading to a low confidence
forecast. So for now, just painted a picture of a trough passing
through Yap and Palau. Even if no development happens, this is still
a reasonable possibility, although the timing might need adjustment.
At this time small craft and high surf advisories are a possibility,
everything will depend on the future behavior of 97W.

&&

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

$$

Kleeschulte/Stanko



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