Tropical Weather Discussion
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AXPQ20 PGUM 302126

Tropical Weather Discussion
National Weather Service Tiyan GU
726 AM ChST Tue Jan 31 2023

Tropical Weather Discussion for the Western North Pacific between
the Equator and 25N from 130E to 180. The following information is
based on recent satellite imagery/data, weather observations, radar,
and meteorological analysis.




The near equatorial trough passes south of Mindanao and enters the
Micronesia area near 4N130E. It heads southeastward to end at EQ134E.
Moderate convection is located between the equator and 4N from 130E to
138E, or in extreme southern portions of the Republic of Palau.

A trade-wind trough curves from EQ147E to 10N142E to 20N145E to
25N153E and farther northeast. Surging trade winds converging into the
trough are igniting moderate convection along and within 120 miles of
a line from EQ156E to 10N139E. This is just southeast of Yap and well
south of Chuuk.

A trade-wind surge is creating a large area of 15 to 25 knot trade
winds between 5N and 21N from 142E to 180. Areas of low-level clouds
and patchy light showers are moving through these winds.

The shear line that looked like it was weakening yesterday has been
revitalized by the emergence of an anticyclone in the mid latitudes,
near 30N125E. ASCAT shows a ribbon of 20 to 30 kt winds north of a
line from 15N130E to 25N148E. The winds extend up to 300 miles north
of the shear line at the west end, diminishing to very little at the
east end. Extensive low-level clouds and patchy showers also cover
this area. This includes the farther north islands of the CNMI.

The near equatorial trough has retreated further and is now squeezed
into the very corner of Micronesia. It`s rather likely to be forced
out of Micronesia completely, in which case it wouldn`t be mentioned
again until it enters the area once more.

The trade-wind trough arcs from just west of the trade-wind surge to
just south of the shear line, providing some sort of connection to the
2 features. This trough is mainly active south of 10N where it has
deep tropical moisture and vigorous convergence from the trade-wind
surge. It is expected to continue moving west with little change in
intensity, affecting Yap later this morning and Palau this afternoon
and evening.

The trade-wind surge is gradually weakening, but still has plenty of
energy left for a few more days. It will continue to affect Chuuk
state and eastward through that period. It is expected to also show a
gradual westward expansion, which has it reaching the Marianas.

The shear line has begun moving south again, at least east of 130E. It
is still a ways north of the Marianas forecast zones. It is expected
to maintain its current intensity through Wednesday with a southward
shift in position. The uncertainty lies in how far south. At this time
it is expected to stall out just north of the Marianas Waters near


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