005
AXPQ20 PGUM 310105
TWDPQ

Tropical Weather Discussion
National Weather Service Tiyan GU
1105 AM ChST Thu Jul 31 2025

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...
Tropical Storm 12W "Krosa" is north of Guam`s AOR. The southwest
monsoon flow into Krosa continues to gradually weaken, as evident
by less convective development with increased spacing between the
showers and thunderstorms in general. However, a general
southwest monsoon axis centered on a 20N130E to 25N145E axis is
present before turning north as it wraps into the circulation.
Here, model data and incoming scatterometer observations suggest a
20 to 30 knot inflow within ~400 miles of this axis.

...OTHER WEATHER SYSTEMS...

TRADE-WIND TROUGHS...
A trio of troughs are seen in the streamline analysis today, One
is located just west and another just east of Majuro. These
troughs feature little convection. A third more active trough is
crossing the Date line. These troughs will continue east over the
next few days, with convective details talked about in the ITCZ
section below. A separate trough further northwest extends from
north of Chuuk to west of Bikini Atoll. Here, modest surface
convergence and good divergence aloft on the south side of a TUTT
is helping promote scattered shower and isolated thunderstorm
development.

TUTT...
A fairly pronounced TUTT extends southwest from TUTT cell at 25N180
to a TUTT cell over Wake Island, then to 10N160, dropping south
on its orientation to end between Pohnpei and Kosrae. Most of the
convection is found along the TUTT cell circulations, and along
the southern and eastern side of the TUTT axis. Taking a look at
the MIMIC water vapor imagery with GFS 200mb analysis overlaid and
comparing them to the latest GFS 200mb and ECMWF 250mb forecasts
for the same time (now), the TUTT cells near the Date Line and
Wake Island aren`t shown in the model data until F24 or F30, with
the same effect on the TUTT axis (more defined now that in model
forecasts).

Thus, it looks like the GFS and ECMWF are about 24-30 hours "late
to the game". That said, they both depict the overall pattern
remaining with regard to these features for the next few
days before a possible change in the pattern occurs.

...ITCZ...
The ITCZ is less pronounced than yesterday and has fragmented into
a segment from Majuro east to just beyond the Date Line, centered
between 4N and 8N. A weakening trough just west and east of
Majuro, and an area of modest convergence is found at the Date
Line where a third trough is found. The first two troughs (just
west and east of Majuro) aren`t doing much aside from providing
cloudy skies, aided by divergence aloft, with warming cloud tops
and just a few showers observed on satellite imagery. The better
convection, in terms of coverage and intensity, is found near the
Date Line trough where cloud top temperatures are pushing -75 deg.
C.

Model forecasts suggest the ITCZ will continue to gradually
weaken, with occasional flare-ups briefly possible (especially
nocturnal), but in general it`ll dissolve in 60 hours (by Sunday).

$$

Doll