548
AXPQ20 PGUM 190105
TWDPQ

Tropical Weather Discussion
National Weather Service Tiyan GU
1105 AM ChST Fri Jul 19 2024

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...
JTWC Invest 92W has drifted northwestward with latest scatterometer
visible satellite showing 92W centered around 11N133E, embedded
within the monsoon trough, and located northwest of Palau and Yap.
Model trends over the next 5 to 7 days favor further development of
92W as continues to drift northwest into the Philippine Sea, but over
the next 24 hours, development of 92W in a tropical cyclone is very
unlikely. Over the last 24 hours, shower and thunderstorm activity,
which was much more widespread across the monsoon trough, is
starting to loosely consolidate around 92W ans long the trailing line
of convergent flow that extends from 92W and southeast towards
Ulithi in Yap State.

...OTHER WEATHER SYSTEMS...

MONSOON TROUGH...
The monsoon trough has started to lift northward, now extending from
the Invest 91W near the Philippines, and enters western Micronesia
at 12N130E and heads southeast, passing through Invest 92W and
passing north of Yap Proper ending near 10N147E, south of the
Marianas and in far western Chuuk State. As mention above,
scattered to numerous showers and isolated thunderstorms are
becoming more consolidated around 92W and the convergent flow the
extends eastward from 92W to Ulithi. Heaviest showers and
thunderstorms are currently located northwest of Palau near 9N131E
and just east of Yap nearly on top of Ulithi this morning.

The monsoon trough is expected to continue to lift northward as it is
pulled by 92W as it heads northwestward into the Philippine Sea. This
will keep Palau and Yap in west to southwest flow with scattered
showers and isolated thunderstorms expected through the weekend,
thought the potential for heavier showers and thunderstorms will be
favored north of both Palau and Yap.

NEAR EQUATORIAL TROUGH...
With the collapse of the ITCZ near the Marshall Islands, the
northwestward shift of the monsoon trough back into western
Micronesia, and the weakening of the trade-wind surge north of the
Marshall Islands scatterometer shows a weak near-equatorial trough
(NET)extending across eastern Micronesia, south of the major
islands, from about EQ150E, up to 5N160E, and then exiting the region
around 3N180. Over the last 24 hours showers have decreased across
Pohnpei and Kosrae and event across the Marshall Islands, leaving
only spotty showers across the region. Models suggest the NET will be
a short-lived feature as it slowly dissipates and is replaced by
trade-wind troughs moving from across the Date Line, slowly
increasing showers across the region.

TRADE-WIND TROUGHS...
Satellite imagery shows a small trade-wind trough passing to the
north of Pohnpei this morning from about 13N160E to 9N161E. Showers
are spotty to scattered along the trough axis with very little
thunderstorm activity detected by the GLD. This trough is expected to
drift westward towards the Marianas, likely reaching the islands
around Sunday and increasing showers in that location. Another trade-
wind trough is entering the region from across the Date Line, in the
wake the ITCZ that has since dissipated since yesterday. This trough
extends from 13N179E to 4N177W. Scattered to numerous showers and
isolated thunderstorms are developing along this trough. This trough
will move towards the Marshall Islands, bring showers to the islands
this weekend.

TUTT...
The TUTT low, located north of the Marianas or near Iwo To, near
23N146E, has moved very little over the last 24 hours as it is
starting to interact with an approaching mid-latitude upper-level
trough pushing of Japan, stopping it westward progression. The
Global Lightning Detection (GLD) network shows isolated to scattered
thunderstorms mainly east of the upper-level low as the TUTT has
started to weaken. This TUTT is expected to slowly dissipate and may
slowly drift towards the east as it continues to interact with the
passing mid-latitude trough. The second TUTT that was located in the
far eastern edge of the region, just east of the Date Line from
around 30N177E to 20N179E , has also moved very little over the last
24 hours as it interacts with and mid-latitude trough moving towards
Alaska. Convection is very spotty underneath this TUTT, with
satellite imagery showing a thin layer of cirrus along the TUTT. This
TUTT is expect to drift east of the Date Line and dissipate.

$$

Schank