Area Forecast Discussion
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FXPQ60 PGUM 200817
AFDPQ

Area Forecast Discussion
National Weather Service Tiyan GU
617 PM ChST Tue Nov 20 2018

.Marianas Synopsis...
Dry conditions and moderate to fresh trade winds continue across the
Marianas. Well southeast, TD 34W continues to move WNW through Chuuk
State. Buoys show seas between 5 and 6 feet.

&&

.Discussion...
As models have shown slightly better consensus and stayed rather
consistent run-to-run, have made some changes to wind and rain
forecasts starting Wed night. A passage to the SSW of Guam Thu will
help limit the winds farther north into Tinian and Saipan vicinity,
but for all the islands, Thanksgiving Day will be windy. Based on
latest track Guam and Rota could be just inside the tropical storm
force wind swath on Thursday, with slightly stronger winds for Guam.
Winds will eventually subside Thursday night and Friday, becoming
southerly. Models differ some on the precipitation spread, whether
consolidated near the center or spread outward. For now have gone
with heavier and more widespread showers for Guam and Rota Thu and
scattered elsewhere. Wet weather will linger into Friday before drier
weather returns in time for the weekend. The only caveat to the
forecast is that if 34W is slower to move tonight and Wed, the
time line of approach will be delayed and the period of stronger
winds and precipitation will need to either be delayed or extended.

&&

.Marine...
With increasing certainty on the motion of 34W, have increased seas
and surf for Wed night through Thu. Seas, winds and surf will all
reach hazardous levels by late Wednesday night. Water-based
activities should be avoided through the Thanksgiving holiday until
seas and winds have subsided later on Friday or Saturday.

&&

.Tropical systems...
Tropical Depression 34W was located just under 1000 miles southeast
of Guam at 4 PM, near 4.5N and 155E. It is expected to move west-
northwest and then to the northwest, likely passing between the
Marianas and Yap sometime on Thursday. Public Advisories and Local
Statements are now being issued by WFO Guam with more detail on how
this system will affect each island.

&&

.Eastern Micronesia...
Majuro sits within a trade-wind trough that is producing scattered
showers and a few thunderstorms from Kwajalein eastward to the
dateline. Models suggest that this area will be diurnally active
through Wednesday before weakening into drier trades. I went with
this forecast, however I believe we still have to keep a watch for
another pulse of energy upstream near the dateline and out to
170W. Farther south...Kosrae sits at the very eastern end of the
large circulation that makes up TD34W. To the south and east is
somewhat drier weather that may temporarily push into the island,
but in general, it looks like Kosrae will stay within the west-
east trough axis that extends from TD34W through to the trough in
the Marshalls. Similarly for Pohnpei which may temporarily break
as TD34W pushes westward. However, latest satellite imagery still
shows several pulses of convection moving into the area from the
south. With ASCAT winds showing some 20 to 25 kt winds, I
maintained the headline of conditions hazardous for small craft
and added a high surf advisory for south and west facing shores.
One caution for Pohnpei is that if TD34W lingers much and fails to
move out as expected, winds, rain and seas will also linger.

As 34W gradually develops and moves west-northwestward tonight and
Wednesday, increasing winds and swell will cause hazardous conditions
for small craft and possibly hazardous surf near Chuuk and Pohnpei.

&&

.Western Micronesia...
Chuuk`s weather is being dominated by the passage of TD34W. Refer
to the HLSPQ1, Local Statement, for more details on what to
expect. Look for seas and surf along south and west facing shores
even after the passage of this system farther to the west.

Both Yap and Koror are sitting in a ridge of dry weather in-
between weather systems. Expect weather from TD34W to begin
affecting Yap late Thursday and on Friday with a less of an effect
on Koror...depending on the exact motion of the system. Models
right now all want to move TD34W well to the north once it crosses
140E keeping Koror dry. However, any alteration of this motion,
would make some big changes to Koror`s weather.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...Tropical Storm Watch for GUZ001-002.

Marianas Waters...Tropical Storm Watch for PMZ151-152.

&&

$$

W. Aydlett/Edson


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