Area Forecast Discussion
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
000
FXPQ60 PGUM 142040
AFDPQ

Area Forecast Discussion
National Weather Service Tiyan GU
640 AM ChST Fri Dec 15 2017

.Marianas Synopsis...
Gentle to moderate trades and isolated showers are found across the
Marianas this morning. The buoys are indicating seas of 5 to 7 feet.

&&

.Discussion...
GFS continues to develop a tropical cyclone well south of Chuuk over
the next few days, moving it WNW over the following week. However,
while ASCAT surface wind analysis shows a weak elongated circulation
near 3N150E, satellite shows very little deep convection. The new
12Z ECMWF shows only a large weak disturbance that shows little
development until Wednesday, but stays well south of Guam, not
getting much above 5N. Definitely leaning toward the ECMWF on this
issue, as GFS has a recent history of developing disturbances too
quickly and too far north. What this all boils down to is very
little change in the forecast, with only a couple of tweaks in max
temperatures. Showers should be no more than isolated the next
5-7 days, and the coming week looks fairly dry for the Marianas.

&&

.Marine...
Moderate trades and 5-7 ft seas look good through Saturday night.
With Ritidian exceeding 7 feet at times, have put some 7-footers
into grids for today through Saturday. For next week, low pressure
to the south and high pressure up north should pump the trades up
to fresh-strong across the Marianas waters by Monday, bringing seas
to 10 ft or more by Tuesday. A Small Craft Advisory will likely be
needed as early as Monday night.

&&

.Eastern Micronesia and Chuuk...
The strongest trade-wind convergence has shifted north of Chuuk,
Pohnpei and Kosrae this morning. Nevertheless, modest converging
southeasterly trades can still spark off a few showers and
thunderstorms near Chuuk and Pohnpei thru Saturday. For Kosrae, weak
surface ridging should maintain fair weather until Saturday morning.
The eastern end of the trade convergence zone will prolong unstable
conditions near Majuro until late this evening. This same feature is
going to progress westward and trigger some showers and possibly some
thunderstorms near Kosrae Saturday and Saturday evening, and around
Pohnpei and Chuuk Saturday night and Sunday. Much drier fresh to
strong northeasterly trade winds can be seen just east of the
Marshall Islands. These winds will bring pleasant but breezy
conditions to Majuro and Kosrae by Sunday, Pohnpei and Chuuk by
Monday.

Moderate trade-wind swell and wind waves should keep marginally
hazardous surf on Kosrae thru Saturday afternoon. Starting Saturday
night and Sunday, trade-wind swell and wind waves will build higher
across the entire region. This will spread hazardous surf to the
Marshall Islands and possibly to Pohnpei and Chuuk States. Seas from
Chuuk State eastward to the Marshalls might also reach Small Craft
Advisory levels. Finally, a new King Tide cycle will start this
weekend. Therefore, need to monitor for possible inundation on Kosrae
and Majuro.

&&

.Western Micronesia for Yap and Koror...
Tropical Storm Kai-Tak has formed just east of the central
Philippines near 11N127E. Fresh to strong monsoonal southwest winds
south of Kai-Tak will continue to generate small areas of convection
toward Koror thru Saturday. For Yap, gentle to moderate trades north
of the monsoon trough should keep relatively fair conditions thru
Saturday. A weak circulation embedded within the monsoon trough has
shifted a bit westward to 3N148E. This system is expected to continue
a slow westward movement over the next few days. Gradual development
is possible as it tracks south of Yap and Koror. Converging winds
northwest and north of the circulation will begin to trigger sporadic
convection near Yap and Koror by Saturday afternoon. If this system
develop further while passing just south of Koror and Yap, inclement
weather with higher winds and seas are possible for both locations
early next week.

A building southwest swell generated by the monsoonal winds south of
Kai-Tak will cause surf on Koror to rise and reach hazardous levels
today thru Saturday.

&&

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

&&

$$

Middlebrooke/Chan



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.