679
AXPQ20 PGUM 170058
TWDPQ

Tropical Weather Discussion
National Weather Service Tiyan GU
1058 AM ChST Fri Jul 17 2026

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.

...SPECIAL FEATURES...

TROPICAL AND MONSOON DISTURBANCES...
Invest 90W, currently remains at a "Low" rating from JTWC (the
Joint Typhoon Warning Center), meaning tropical cyclone
development is not likely within the next 24 hours. 90W continues
to remain quasi-stationary southeast of Chuuk, near Namoluk. This
system remains in a somewhat hostile environment, with wind shear
of 15 to 20 knots noted.

However, more favorable conditions (less wind shear) is located
just north of the region. The wind shear is helping to limit
convective development, with pockets of convection trying to
develop around the LLCC (Low-Level Circulation). These convective
attempts are having some success in developing deeper/taller
updrafts, but, 90W is still fighting the "wind shear battle".
However, as it lifts north, the improved conditions should allow
for an increase in convective coverage and strength.

The overall pattern would favor this "northward jog" starting
sometime over the next 24 hours or so, with a gradual continued
strengthening. Then, about 60 to 84 hours out the system looks to
make more of a westward turn and head towards/through the
Marianas. As it does so, locally heavy rainfall and gusty winds
will probably develop towards the middle of next week.

...OTHER WEATHER SYSTEMS...

MONSOON TROUGH...
A relatively broad and dry west to southwest Monsoon Trough
enters Guam`s AOR near 8N130E and extends across Koror and Yap,
extending northeast across Guam and the CNMI where it moistens
somewhat. This is due to an upper low northwest of the CNMI near
IWO To, which is helping funnel moisture cyclonically across the
Marianas. Over the last 36 hours, this trough has increased it`s
moisture depth and this is "influx" of moisture is expected to
continue over the next few days, possibly increasing convective
coverage across the Marianas.

NEAR-EQUATORIAL TROUGH...
A NET (Near-Equatorial Trough) extends from a col north of Chuuk
southeastward in an arcing form to another col just west of
Kwajalein. It then continues east to a circulation northeast of
Majuro near 9N179E, before exiting Guam`s AOR at 9N180. This
trough is more a wind flow change, with broad westerlies south of
it and easterlies north of it. Most of the convection found near
the NET is southwest to west of Chuuk between 5N and 10N, from
145E to 150E. Here, widespread showers and scattered thunderstorms
are developing as an elevated vorticity center interacts with
both the tail end of the NET, and Invest 90W southeast of Chuuk
(with the low-level cyclonic flow is helping with moisture
advection into this convective development).

Then, once you get east of this convection and 90W, the cross-
equatorial southwesterly flow continues, with scattered showers
fairly common between the equator and the NET from 150E to 170E.
This coverage of showers then diminishes east of there due to
weaker flow/convergence. This pattern looks to change by early
next week though, as 90W gradually develops and lifts north then
west-northwest, allowing for the NET to reorientate itself.

OTHER SYSTEMS...
A mid-latitude trough axis has overtaken the TUTT axis, and now
stretches from 20N180 southwest to 12N170E, before curving
northwest and connecting with an upper low well east of the
Marianas near 17N155E. This trough then extends southwest to north
of Chuuk near 11N151E, where it ends. The main feature associated
with this trough of note is increased upper level moisture north
of the trough as cold advection helps to create instability
showers. With that said, the trough will peel east of the region
over the weekend, with 90W also moving towards the Marianas,
helping to induce a pattern change.

$$

Doll