FXPQ60 PGUM 230753
Area Forecast Discussion
National Weather Service Tiyan GU
600 PM ChST Thu Nov 23 2017
A fairly dry trade-wind regime remains anchored over the Marianas.
Satellite shows only patches of clouds drifting along with the
winds. The buoys show combined seas of 6 to 7 feet and sea surface
temperatures of 84 to 85.
If dry season has not yet arrived, it is clearly on its way. Shear
lines are reaching down to northern Luzon now and the precipitable
water on our sounding this morning was only 1.24 inches. Clouds
are expected to increase a bit starting Sunday night, however
rainfall should remain limited. Soon, the main concern could be
fire weather if these current model runs verify. The main story
for now is increasing winds and seas; for more on that, please see
the Marine section below.
Combined seas of 6 to 7 feet will remain more or less steady
through Saturday. After that, increasing winds will cause them to
rise. They are expected to reach 8 to 10 feet Saturday night or
Sunday. Winds are expected to reach small craft advisory criteria
before that, so mariners are urged to remain aware of the latest
advisories and forecasts.
A fairly dry pattern is now in place across most of Eastern
Micronesia. The eastern edge of a band of trade-wind convergence is
still producing scattered showers over Pohnpei, but these showers
are continuing to move westward and will no longer affect Pohnpei
later this evening. Dry conditions now over Kosrae to Majuro will
continue over the next couple of days. A trade-wind surge will bring
a wet pattern back to the Marshalls Saturday night with scattered
showers possible through the beginning of next week. By the
beginning of next week, a new convergence pattern will develop over
the region that will maintain scattered showers at Majuro through
Tuesday and increase showers at both Pohnpei and Kosrae by Tuesday.
Winds and seas will rise in the Marshalls late in the weekend, and
could approach levels hazardous to small craft operations and
produce hazardous surf conditions. Seas, winds and surf will also
build some at Pohnpei and Kosrae.
A weak circulation is centered south of Koror near 4N134E. A
near-equatorial trough stretches eastward from 1N130E through the
circulation to end near EQ150E. A band of convergence north of
the trough and circulation is generating scattered showers and a
few thunderstorms from Chuuk to southeast of Yap and also south of
Koror. A few showers and thunderstorms have also developed near
Yap this afternoon, but are expected to be short-lived. Latest
model guidance shows an increase in convergence from Chuuk to
Koror resulting in scattered showers at Chuuk through Friday
afternoon and at Koror through Saturday night. The band of
convergence looks to remain far enough south of Yap so that
showers will remain isolated. A drier pattern will then move in to
chuuk from Eastern Micronesia and spread westward to Yap and
Koror by Sunday.
Trade winds are expected to become fresh to strong Friday and
Saturday for Yap and Koror. Winds are expected to reach small craft
advisory levels on Friday at Yap , but remain just below for Koror.
Seas are currently forecast below small craft criteria at all three
forecast points for now, however, seas will be monitored for
possible small craft criteria over the next couple of days, with
seas coming close to the 10 ft threshold. Surf along north and
east shores will also rise and could reach hazardous surf heights
for the weekend.
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