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AXPQ20 PGUM 160141
TWDPQ

Tropical Weather Discussion
National Weather Service Tiyan GU
1141 AM ChST Thu Jul 16 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 from JTWC has formed southwest of Pohnpei/southeast of
Chuuk, near Nukuoro. The LLCC with 90W continues to slowly
organize, but recent satellite imagery shows convection is
increasing near the center, with the latest HSCAT also showing a
WWB of 20 to 25 knots. One thing that remains evident in visible
imagery is a fairly strong cross-equatorial flow, some of which
looks to be getting absorbed into 90W. The pattern remains
conducive for further development as well. As such, we expect 90W
will remain quasi-stationary for the next 24 to 48 hours, before
lifting north somewhere between Chuuk and Pohnpei States, likely
during the latter half of the weekend or early next week. This
tropical disturbance will bring some locally heavy rainfall and
gusty winds to much of Pohnpei, Chuuk, and eastern Yap States
through Monday, and Special Weather Statements have been issued by
to address these concerns.

After the disturbance leaves the FSM, where will it go and how
organized will it be remains to be seen. In general, we do expect
a gradual turn towards the Marianas by the middle of next week.
Here too, locally heavy rainfall and gusty winds may develop, but
it`s STILL WAY TOO EARLY TO GET SPECIFIC in the details, as the
tropical disturbance is just starting to slowly attempt to
organize. Folks across the FSM and the Marianas should remain
vigilant to forecast updates over the next several days.

For more information please visit www.weather.gov/gum


...OTHER WEATHER SYSTEMS...

MONSOON TROUGH...
A dry monsoon trough has developed and enters Guam`s AOR near
7N130E. It then extends northeast across Koror and Palau,
continuing northeast across Guam and much of the CNMI. No
appreciable convection is observed along the trough until you
reach the northern half of the CNMI. This is due to ALPWs being
near 1 inch in the drier locations. A nearby TUTT and cell is
providing good divergence aloft and helping to focus the
convective development across the CNMI. This pattern looks to
remain stagnant for another 24 to 48 hours, before a pattern
change potentially begins.

NEAR-EQUATORIAL TROUGH...
The NET enter`s Guam`s AOR near 6N130E, then extends east-
southeast to Invest 90W near Nukuoro. It then continues east-
northeast through Kosrae and Majuro, before exiting Guam`s AOR at
9N180. Isolated to widely scattered convection is occurring south
of the NET from 130E to 143E. Then, convection increased along and
near the NET INVO 90W, with good poleward outflow aloft helping
maintain convective updraft organization and longevity. The NET
then remains convectively active along and south of the NET for
the remainder of it`s journey through our AOR. Most of the
convection outside of 90W has been scattered in nature, but
locally intense as cloud top temperatures surpassing -70 deg. is
supportive of heavy rainfall. Looking ahead, we expect the NET to
remain near it`s current orientation, modulated by wave
propagation along it through early next week.

TUTT...
A hybrid TUTT/mid-lattitude trough axis enter`s Guam`s AOR near
15N180 and extends west, then northwest to a cell near 18N156E. It
then extends southwest to near Rota, where it ends. The cell near
18N156E is flanked by a pair of upper-level highs, with one
centered near Minamitorishima, and the other northwest of
Enewetak/north of Pohnpei near 15N160E. This is playing havoc on
the TUTT pattern, as divergence commonly found south and east of
the TUTT axis is lacking, with a dry airmass present in WV imagery
along and near the TUTT, except between Rota and 160E, where
moisture from 90W is getting pulled north.

Farther north and west, a TUTT-like cell is anchored near Iwo To,
with it`s trough axis extending south to a col near 19N135E,
where it ends. This axis is not too far displaced from the TUTT
ending near Rota, and WV loops suggest the two are interacting
with once another, albeit modestly.

Never-the-less, this pattern looks to hold for another 48 to 60
hours, before a pattern reorientation takes shape, likely forced
by 90W attempting to strengthen as it lifts north, sometime during
the first half of next week.

$$

Doll