Area Forecast Discussion
Issued by NWS
FXPQ60 PGUM 270616
Area Forecast Discussion
National Weather Service Tiyan GU
342 PM ChST Sat Aug 27 2016
PGUA Doppler weather radar shows almost no showers within the
Marianas waters. The VAD wind profile reveals light and variable
winds in the lowest 2 thousand feet of the air. This morning`s
weather balloon shows the winds become southeast above this. Above
10 thousand feet the winds turn toward the east and increase to
between 15 and 25 knots. Above 30 thousand feet they turn toward
the northeast and increase further to between 40 and 60 knots.
Expected island convection largely fizzled...most likely due to
the high winds aloft. Main forecast issue is going to be swell
from Typhoon Lionrock. If it grows any bigger, which is expected
Sunday night, we will likely need a high surf advisory on north
and west facing reefs. Later next week we may even need a small
craft advisory if the southwest winds start increasing, as shown
in the GFS and the NavGem, and to a lesser extent in the ECMWF-
HiRes. Generally, the models expect less than a half inch of rain
fall the next 10 days, so weather will be rather dry. Wind and
waves will be the big story this coming week.
A surface trough with a few showers lingering over Pohnpei State
is moving slowly toward Chuuk this afternoon. Light southeast
winds and fair weather prevail over Kosrae State. Farther east, a
trade-wind disturbance is edging from across the Date Line into
the Marshall Islands. Converging southeast winds will trigger some
showers for Majuro overnight, and the disturbance will move
westward and cause increasing showers and possible thunderstorms
for Majuro through Sunday at least, and then for Kosrae on Sunday
through Monday, and probably to the Pohnpei and Chuuk areas by
Monday or Tuesday. In the longer term, weather conditions will
depend to some degree on the more active weather developing
farther north near Wake Island, but generally fair weather is
expected most of next week.
Distant Typhoon Lionrock is moving toward the northeast with a
large fresh to strong wind field. A slow northeast track will
allow some of the long-period northwest swell to affect Chuuk,
Pohnpei and Kosrae States during the first half of next week.
While seas are not expected to reach hazardous levels, surf
conditions will need to be monitored.
Reasoning for the Chuuk forecast can be found in the Eastern
Micronesia section above.
A ridge of high pressure will provide light winds and partly cloudy
skies for Koror and Yap the next few days, except for a possibility
of brief afternoon thunderstorms near Koror due to island heating.
Next week, a moderate southwest monsoon flow could develop across
far Western Micronesia.
Long-period northwest to north swell generated by slow-moving
Typhoon Lionrock much farther north will affect Palau and Yap State
the next few days. Seas and surf will gradually rise thru Tuesday.
Even though seas are not expected to be high enough for small craft
advisory, waves heights will need to be monitored for possible