Area Forecast Discussion
Issued by NWS
FXPQ60 PGUM 242135
Area Forecast Discussion
National Weather Service Tiyan GU
724 AM ChST Mon Jul 25 2016
.Synopsis...Light east winds and a few showers prevail across
the Marianas this morning.
A surface trough could be found on last nights surface analysis
just to the west of the Marianas. This trough brought a few
showers and thunderstorms Sunday and early this morning. Weak
high pressure in the wake of the trough will bring Mostly Sunny
skies to the area today. Another surface trough could be found
east of the Marianas. This trough will move west and pass across
the local area late tonight and Tuesday.
This mornings satellite imagery did show showers and thunderstorms
associated with the trough to our east. Models depict showers
moving over the Marianas as the trough passes, mainly after
midnight tonight and part of Tuesday. Lightning was detected with
the trough so isolated thunderstorms are possible tonight and
Tuesday. Not certain if the scattered showers associated with the
trough this morning will persist through tonight so just left
shower coverage as isolated.
Models show low-level convergence Tuesday night through Wednesday
night plus another surface trough passing over the Marianas on
Thursday. Extended the mention of isolated thunderstorms through
Thursday night in the forecast. Models depict shower coverage as
patchy and while brief period of showers are possible overall
coverage should remain isolated.
Ritidian, Ipan and Tanapag buoy data show combined seas of around
2 to 3 feet this morning. A east trade-wind swell will be present
through the forecast. Swell period was 13 seconds and WW3 models
does show this. Also Ritidian and Tanapag buoys still depicted a
small north swell. As no significant weather systems are expected
through the week which might increase winds or swell neither the
east swell nor the north will become too large. With winds staying
around 10 knots through the forecast, expect wind waves to remain
at around 2 feet through the week. Surf is predicted to be at 2 to
4 feet on east facing reefs and 1 to 2 feet on north, west, and
south facing reefs The rip current risk will be low through the
Trade-wind convergence and upper-level divergence are producing
cloudiness and scattered showers with isolated thunderstorms in
several areas across Chuuk and Pohnpei States into western Kosrae
State. Models indicate the pattern will not change much but should
be drifting westward very slowly. Also, a surface trough is moving
from across the Date Line toward the Marshall Islands and it will
produce showers at times for Majuro the next day or two at least.
The trough will likely continue moving westward across Eastern
Micronesia during the next several days. Majuro/Kalo Buoy shows
combined seas of 4 to 5 feet.
Reasoning for the Chuuk forecast can be found in the Eastern
Micronesia discussion above.
Some forecast changes were made for Yap and Koror based on latest
model guidance. Ascat Analysis indicates a weak circulation near
6N143E with a surface trough extending northwest over Yap State.
Areas of showers and a few thunderstorms are between Koror and Yap
and northeast of Yap. GFS indicates the circulation will drift
toward west-northwest and slowly develop during the next few days,
so it will need to be monitored closely. The Yap and Koror weather
will be changeable during the next few days, and later in the week,
another trough arriving from the east could bring more clouds and
showers back to far Western Micronesia.