High Surf Advisory 8, NWS Guam

Area Forecast Discussion
National Weather Service Tiyan GU
337 PM ChST Fri Aug 12 2016

.Synopsis...
A developing circulation, JTWC invest area 93W, is centered well
west of Saipan near 17N 138E. South of 93W, the monsoon is
surging toward the Marianas with narrow lines of showers seen on
visible satellite imagery west of the region, moving towards the
east. Southwest winds are currently moderate, and seas are between
6 and 7 feet at the buoys.

&&

.Discussion...
Latest models still show 93W developing over the next few days and
moving north to northeast. The GFS takes it northeast, with a
surge of monsoon southwest flow building across the Marianas over
the weekend into next week. The ECMWF takes 93W more to the north,
but still keeps a fairly strong westerly flow across the Marianas
into next week as well. Refreshed winds the next few days from the
GFS75, which increases winds slightly tonight through the weekend.
Should be breezy into the middle of next week, with windy
conditions up to 30 mph on Sunday. Have trimmed back to isolated
showers and thunderstorms for tonight and Saturday, as the last
2 runs of the GFS have kept most of the showers west of the marine
zones through Saturday. Further out, have backed off on numerous
heavy showers for Sun through Tue night, as models have tended to
pull the heaviest bands of showers up to the north, which seems
likely given that 93W will be tracking north of northeast fairly
quickly and should pull the monsoon tail up north with it. There
is plenty of uncertainty in this situation, and periods of locally
heavy rain are still possible some time next week.

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.Marine/Surf...
Have issued Small Craft and High Surf advisories starting tonight
as winds and seas are due to rise overnight, and persist for
several days.

&&

.Tropical systems...
93W is quite disorganized on satellite imagery, but development
potential remains high. Model consensus takes it well north of
Saipan over the weekend. The main effects in the Marianas should
be locally heavy rain at times, breezy conditions and hazardous
seas and surf.

&&

.Eastern Micronesia...
Fair weather and light east winds prevail at Pohnpei and Kosrae
today, but a trade-wind disturbance is causing showers east and
northeast of Majuro. Although the disturbance is moving very slowly
westward across the Marshall Islands, and most heavier showers will
be north of 8N, some cloudiness and showers will move to Kosrae on
Saturday or early Sunday, and probably to Pohnpei on Sunday and
Monday. Majuro/Kalo Buoy shows combined seas of 3 to 4 feet.

&&

.Western Micronesia...
Satellite shows a band of heavy showers and thunderstorms persists
between 9N and 12N from 130E to 141E. Also, high-level clouds are
streaming across far Western Micronesia. Ascat winds show a surface
ridge remains east-west between the Equator and 5N. Otherwise, the
monsoon trough and a developing circulation near 17N138E remain
well north of Yap. GFS Model indicates moderate to fresh monsoon
west to southwest winds will continue to develop across the
Republic of Palau and Yap State in the coming days, and shower
coverage will increase this weekend.

Tropical Storm Conson is moving far away, and the southwest monsoon
flow is weaker across Chuuk State today. Very active weather will
continue over the Northwest Pacific, but for Chuuk, southwest winds
and showers will taper off, then light south to southeast winds and
just isolated showers are expected through early next week

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...High Surf Advisory until 6 PM CHST Monday for GUZ001>005.

Marianas Waters...Small Craft Advisory until 6 PM CHST Monday
     for PMZ151>154.

&&

Middlebrooke/Simpson