Area Forecast Discussion
Issued by NWS
FXPQ60 PGUM 230909 CCA
Area Forecast Discussion
National Weather Service Tiyan GU
645 PM ChST Mon Jan 23 2017
Partly to mostly cloudy skies and fresh to strong winds prevail
across the Marianas. Latest PGUA WSR-88D data shows isolated showers
southeast of Guam. Buoy observations show combined seas ranging from
9 to a little over 12 feet.
An overall dry pattern is now in place over the Marianas. The shear
line to the south that was expected to drift back north continues to
weaken and is no longer expected to bring anything more than a slight
increase in showers to the islands. The main concern is with winds and
cloud cover. Fresh to strong winds are expected to continue across
the region for the next couple of days, then begin to subside
Wednesday night or Thursday.
Latest readings at Ritidian buoy show combined seas have risen to
around 12 feet this afternoon. North swell continues to be the most
dominant, however, persistent fresh to strong northeast winds are
helping to build the northeast swell as well. Combined seas are
expected to peak around 12 to 13 feet Tuesday. Winds and seas are
expected to remain hazardous to small craft through at least
Thursday. The strong north swell will maintain hazardous surf
conditions across the islands through Thursday as well. Surf is
currently between 9 and 12 feet on north and west exposures and is
likely to build another foot by Tuesday, before beginning to slowly
subside. the building northeast swell and wind waves will also
generate hazardous surf conditions along east facing exposures. Surf
is expected to be borderline on east facing reefs, but decided to add
east facing reefs to the High Surf Advisory mainly due to the High
Risk of rip currents on these shores.
Followed the trend for drier weather for Majuro and Kosrae over the
next couple days. As indicated previous forecast package, organization
along the ITCZ appears to be weakening and this is also seen in the
GFS and ECMWF...as well as in the satellite imagery. Although current
observations show only isolated showers in the vicinity of Pohnpei,
satellite imagery and NWP models indicate that the scattered
showers and thunderstorm activity currently in the western Marshalls
is likely to head towards Pohnpei over the next couple of days. Then,
after a brief period of drier weather...models suggest another round
of scattered showers for Pohnpei starting over the weekend. However...
this forecast sticks with isolated conditions for now until we see a
similar run or two in the next couple of NWP packages.
Large trade-wind swells and wind waves generated by the extensive frontal
zone to the north continue to maintain hazardous surf and seas over all
our designated islands in Micronesia. Although the Wave Watch III wave
model shows a let up by mid week...it brings back the 10+ footers over
the three islands by the end of the week. Since most of the push is
from the east-northeast the affected coastlines are primarily along
the east-facing shores. However, some of the energy and an enhance risk
of rip currents is also affecting the north-facing shores, as well.
Winds and seas are slightly below our advisory criteria for small craft
in the Majuro coastal waters so I have dropped this remark in the forecast.
However caution is still advised for those in smaller vessels as conditions
are not below this criteria by much.
Corrected Typo in last paragraph
Forecast for Chuuk goes along with the previous forecast. Most of the
shower activity is currently in southern Chuuk State but models have
this area of convergence north of a weak equatorial trough moving in and
out of the Chuuk Coastal Waters through at least Thursday...and possibly
into the weekend. Its been raining steadily today in Yap with the
active shear line just to the north pushing one set of showers over the
area after another. The models don`t handle this very well but with the
latest trend in the satellite imagery pushing the southern
boundary farther to the north of the islands, I`ve gone with a
lower confidence change to isolated after midnight. At least both
the GFS and ECMWF weather models think it is supposed to be pretty
dry over Yap until sometime on Wednesday.
Similar forecast pattern for the Republic of Palau...however they don`t
have to deal with the shearline...except for the winds and seas which
seem to be affecting everyone. In fact, the WW3 has the trend to go up
to 12 to 13 feet for combined seas for Yap and portions of the northern
ROP. This has prompted us to maintain the high surf advisory and
the discussion concerning hazardous conditions for small craft for
both Yap and Koror...until mid week. Chuuk`s sea conditions are
more temporary and should only provide hazardous conditions for
the next day or two.
GU...High Surf Advisory until 6 PM CHST Thursday for GUZ001>004.
Marianas Waters...Small Craft Advisory until 6 PM CHST Thursday