Area Forecast Discussion
Issued by NWS
FXPQ60 PGUM 270735
Area Forecast Discussion
National Weather Service Tiyan GU
458 PM ChST Mon Mar 27 2017
.Marianas Synopsis...The Marianas will remain under a high
pressure trade-wind regime for another day or two while heaviest
rainfall remains well to the south near the equator. Latest
satellite imagery shows the shear line to the north only weakly
approaching. Still...a couple of isolated showers in the region
are indicated in the imagery that might pass overhead to provide
a temporary cooling off period for those lucky enough to be in
the right location.
.Discussion...Little change from the previous forecast.
Models...primarily the GFS, ECMWF and NAVGEM...still show a weak
shear line passing through the Marianas late Wednesday into
Thursday. As these go, this one seems a bit drier than the past
ones so we have kept the precipitation at isolated with just an
increase in cloud cover during these days. Winds don`t really
look that strong either, but have kept the previous wind forecast
with a possibility of winds approaching 25 knots offshore on
Wednesday. GFS and NAVGEM show this for a portion of Wednesday
afternoon, but ECMWF has a little weaker flow. Next feature after
this is not until the end of the weekend or early next week...but
this is purely conjecture on the part of the models at this time.
.Marine...We have the current low risk of hazardous rip currents
increasing with the winds and swells on Wednesday and Thursday.
This might be a border line small craft advisory situation. Seas,
however, look likely to make it to 8 to 9 feet, split between the
north east sides and so not thinking of high surf advisory
conditions at this time.
ASCAT Analysis shows an Inter-Tropical Convergence Zone is producing
heavy showers from Kosrae across Majuro to near the Date Line, and
other heavy showers are over southern Chuuk State. Partly cloudy
skies remain over Chuuk and Pohnpei this afternoon. The GFS Model
indicates this pattern of convergence and showery weather will move
westward during the next few days. Showers and thunderstorms will
continue to spread over Kosrae to Pohnpei tonight, and to Chuuk on
Tuesday. The showery weather should taper-off at Majuro on Tuesday.
A relatively wet east-northeast flow could continue across the area
most of this week. Majuro Buoy shows combined seas around 7 feet.
Also, very dry weather remains over the northern Marshall Islands.
Swell and wind waves associated a trade-wind surge will continue to
produce hazardous surf and minor coastal inundation at Kosrae and
Majuro through the middle of the week. As this surge moves through
the Marshalls, wind and seas will be hazardous for small craft
tonight and Tuesday. Although High Surf conditions are not expected
at Majuro, minor coastal inundation on east facing reefs remains
possible during high tide. Wind and seas are expected to begin to
subside this evening at Majuro, falling below Small Craft Advisory
levels by Tuesday morning.
The Chuuk forecast discussion is included with Eastern Micronesia
Pleasant weather prevails over Yap and Koror for the near term, but
unstable weather is expected to develop over far Western Micronesia
by Wednesday through Thursday or Friday as a pattern of convergent
winds combined with moisture from a fairly active equatorial
trough arrive from the east and southeast, respectively. There
could be times of heavy rainfall, especially for Koror about
Increasing swell and wind waves associated with a trade-wind surge
are still expected over Western Micronesia in the coming days. Small
Craft Advisory levels are not expected at this time, however, seas
will be a little rougher than normal and mariners should use more
caution for inter-island travel. If the seas do reach hazardous
levels, it will occur mainly Wednesday and Thursday.