Area Forecast Discussion
Issued by NWS
FXPQ60 PGUM 190903
Area Forecast Discussion
National Weather Service Tiyan GU
616 PM ChST Thu Jan 19 2017
Weather radar shows scattered showers remain
over Guam and the Guam coastal waters with only isolated
showers elsewhere. The VAD still shows winds of 30 kts
just above the surface which is reflecting in both the
Guam and Saipan surface observations in terms of gusts
to 25 kts...about 5 kts less than yesterday. Guam and
Saipan buoy reports are still sticking with that pest
north swell and topping 11 to 12 feet. Overall satellite
imagery continues to show the frontal zone breaking down.
A consensus of the 3 NWP models that are easily
available in the office: GFS, ECMWF and NAVGEM gives pretty much
consistent indication that we are seeing the last of the winds
and rains over the Marianas from this current frontal episode.
Except for the possibility of a remnant shear line from the south
pushing back over the Marianas on Sunday, weather looks pretty
good until Tuesday or Wednesday of next week when the frontal
system is expect to approach the area. The timing and intensity
of this event is still speculative, but it does not look nearly
as large or deep as the one we just had.
Buoys at Ritidian and Saipan are still reporting 11 to
12 feet with the north swell diminishing...but slowly. Altimetry
also shows the belt of 9 to 12 feet waves to our north is also
thinning out. With these observations...and the WW3 wave model,
I`ve decided to not extend out the high surf advisory any further,
with the caveat that we will re-evaluate in the morning. All
models say we will down below 8 feet by the weekend. However, I
extended the small craft advisory...which can be easily
discontinued if necessary during the day tomorrow if conditions
warrant as I figured, that besides with the seas just short of 10
feet in the morning, we are also still likely to see sustained
winds to 20 kts over the coastal waters which would result in a
SCA criteria be met with frequent gusts of 20 to 25 kts.
Fresh to strong, dry trade winds prevail across the Eastern
Micronesia region from Chuuk to Majuro. Vis satellite does show a
cluster of clouds and showers passing over Majuro this evening.
Trade wind showers and thunderstorms are suppressed well to the
south between the equator and 3N. This dry pattern will persist into
the weekend with fresh to strong trades across the region. For the
long range, models indicate a bit more moisture across the region as
convergence increases and patchy showers will return early next week.
Far northern Marshall Islands remain very dry. Both ECMWF and GFS
show only about a half inch of rainfall north of 10N through the
next 10 days.
Large north swell at Chuuk, Pohnpei and Kosrae will continue to
subside tonight and Friday. Surf along north facing reefs at Kosrae
has fallen below advisory levels. Large east-northeast trade wind
swell will maintain hazardous surf along Kosrae`s east facing reefs
through the weekend. The combination of long period north swell, the
trade wind swell and fresh to strong winds over the next couple days
will produce conditions hazardous for small craft at Chuuk, Pohnpei,
Kosrae and Majuro. The Majuro buoy shows combined seas 5 to 6
Chuuk discussion included with Eastern Micronesia above.
Trade-wind convergence is generating patchy showers and a few
thunderstorms over eastern Yap State and the Republic of Palau this
afternoon. Models indicate more showers arriving at Yap and Koror
the next couple days as moisture increases between a surface trough
to the south and a shear line to the north. Relatively drier weather
expected at both locations by Monday.
High Surf Advisories remain in effect for Koror and Yap. A Large
north swell will maintain hazardous surf through Friday. Surf
could subside below hazardous levels Friday night at both
GU...High Surf Advisory until 6 AM CHST Friday for GUZ001>004.
Marianas Waters...Small Craft Advisory until 6 PM CHST Friday for PMZ151>154.