Area Forecast Discussion
Issued by NWS Tiyan, Guam

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FXPQ50 PGUM 252123

Area Forecast Discussion
National Weather Service Tiyan GU
723 AM ChST Wed Feb 26 2020

.Marianas Synopsis...
Partly cloudy skies with spotty showers and gentle to moderate trade
winds prevail across the Marianas this morning. Latest buoy readings
show seas between 6 and 8 feet.


A drier trade-wind pattern is now in place across the Marianas and
looks to continue for at least the next few days. Winds have subsided
a bit as well, with moderate to fresh trade winds through tonight
becoming gentle to moderate Thursday. A shear line is expected to
move into the Marianas over the weekend, resulting in increasing
winds and cloud cover. A weak circulation centered south of
Kwajalein is expected to slowly move toward the Marianas over the
weekend. This system is expected to weaken as it approaches and
move through the region as an open trough. Latest model runs show
little increase in moisture and showers with the trough, though
this is our next best chance at a needed wetting rain.


Seas and winds have subsided this morning, with seas dropping to
between 7 and 9 feet and winds have become moderate to fresh. This
has allowed the Small Craft Advisory to be cancelled this morning.
Seas and winds will continue to slowly subside over the next couple
of days. Seas could reach near 10 feet again late in the weekend or
early next week as a north swell moves in to waters and interacts
with the trade-wind swell and wind waves. Seas are, however,
sufficient to maintain a High Risk of Rip Currents along east facing
reefs through at least tonight. If the east swell remains around 7
feet, the High Risk of Rip Currents may need to be extended.


.Fire weather...
Guam did receive a welcome wetting rain yesterday. This, along with
weaker winds, will help minimize the fire danger in the short term,
though the island does remain fairly dry. Much drier conditions are
expected for the next few days as a very dry trade-wind pattern is
now in place across the region. Another shear line is expected to
move into the area over the weekend. Wetting rains are not expected
with this feature, though that does remain a possibility.


.Eastern Micronesia...
Overnight ASCAT indicates a weak circulation is centered southwest
of Majuro near 3N167E. Scattered to numerous showers and isolated
thunderstorms are found near the circulation and eastward across the
Marshall Islands to the dateline.

Little change to the previous forecast. Expect a wet Wednesday across
the Marshalls as strong trade-wind convergence east of the
circulation continues to generate showers and thunderstorms. Shower
coverage should decrease sometime on Thursday as low-level
convergence decreases. Although GFS and ECMWF still diverge on the
movement of the circulation, both models indicate the southern
half of the circulation will struggle to produce convection.
Therefore, exactly where the weak circulation tracks will determine
the likelihood of widespread showers. Current forecast is still a
blend of the ECMWF and GFS with scattered showers developing at
Kosrae later today and continuing through Thursday night or Friday.
Forecast confidence is still low for Pohnpei so maintained isolated
showers. If showers do increase at Pohnpei, late Friday to Sunday
would be the timeframe. GFS and ECMWF indicate another round of
showers is possible for Majuro late Friday into Saturday. A drier
trade-wind pattern looks to fill in early next week.

Hazardous seas of 8 to 11 feet are expected the next several days at
Majuro due to a broad area of strong trade winds east of the islands.
Elsewhere, seas will gradually subside to 6-7 ft by Sunday.


.Western Micronesia...
Trade-wind convergence is generating showers and thunderstorms south
of Yap and Chuuk...between 2N and 7N.

Little change to the previous forecast. The area of trade convergence
will drift westward the next few days, increasing showers at Palau
by Thursday. Yap still looks to stay on the dry side just north of
the shower activity. Guidance as a whole maintains a dry outlook for
Chuuk as well. There is still a chance the circulation currently
southeast of Kosrae moves west enough to encourage showers over Chuuk
this weekend but confidence is not high with this idea. Expect trade
winds to stay below 20 knots throughout the region with gentler winds
at Chuuk late in the period as the circulation meanders nearby.

Dropped the high surf advisory for Yap and Palau as seas and swell
have subsided enough that 12 foot surf is no longer expected on east
reefs. That said, altimetry passes near Yap came in a bit higher than
guidance so kept seas hazardous for small craft through today. Seas
gradually lower to 6 to 7 feet by this weekend for the region.


GU...High Rip Current Risk through late tonight for GUZ001>004.

Marianas Waters...None.


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