037
AXPQ20 PGUM 180101
TWDPQ

Tropical Weather Discussion
National Weather Service Tiyan GU
1101 AM ChST Thu Jul 18 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...
A broad circulation has developed within the monsoon trough and south
of a trade-wind trough that has been riding along the northern edge
of the monsoon. This circulation is located near 10N137E, or west-
northwest of Yap Proper and north of Palau. The Joint Typhoon Warning
Center (JTWC) is monitoring this feature as Invest 92W. 92W is very
disorganized and will continue to slowly drift westward into the
Philippine Sea and away for Yap and Palau. Further development of 92W
is very unlikely over the next 24 hours. Further information can be
found in the monsoon trough section below.

...OTHER WEATHER SYSTEMS...

MONSOON TROUGH...
The monsoon trough, extending from the Invest 91W near the
Philippines, and enters western Micronesia at 11N130E and heads
southeast, passing through Invest 92W and near the main islands of
Palau and Yap Proper, across Yap State and southern Chuuk and Pohnpei
States, then ending near 3N162E, south of Kosrae. Scattered to
numerous showers and isolated thunderstorms are developing along the
trough, with gusty westerly winds, associated with showers pushing
through Palau and up to Yap State.

The monsoon trough is expected to continue across western
Micronesia, supporting locally heavy showers and thunderstorms at
times at Palau and Yap, along with gusty southwest to west winds
across Palau. Models shows the potential of a north to northwest
shift over the next few days as the monsoon trough follows Invests
91W and 92W, along with any other disturbance that develops near Yap
and Palau. This may also bring gusty southwest winds to Yap Proper,
along with the potential for heavy showers for the Marianas later
this week.

TRADE-WIND TROUGHS...
There are a couple of weak trade-wind troughs near and east of the
Marianas. The first trough extends north of Invest 92W and up to
17N132E. Showers are fairly spotty around this trough, and become
more numerous near 92W. The second trough is passing across the
Marianas this morning and is producing scattered showers, with some
gusty winds up to 33 kts reported within heavier showers at the ASOS
located at airport on Guam. This second trough is likely experiencing
some enhanced upper-level support from the TUTT that extends near
the Marianas and discussed in more detail down below. These troughs
will continue to push westward, but the monsoon trough will keep
showers weather across western Micronesia and near the Marianas the
next few days as discussed above.

TRADE-WIND SURGE...The trade-wind surge continues to weaken and
retreat eastward across eastern Micronesia, with scatterometer
showing 15+ kt winds stretching from 160E to east of the Date Line
and from 8N to 25N. Pockets of 20+ kt winds mainly seen along 180
near 10N and areas east of 180. Pockets of showers are occurring
within the surge, but along the southern periphery, enhanced
convergence with the ITCZ is producing numerous showers and isolated
thunderstorms along the northern Marshall Islands, especially near
and north of Kwajalein. The trade-wind surge will continue to weaken
as the surface high to the distant north continues to propagate
eastward, relaxing the pressure gradient.

TUTT...
There are now two TUTTs within the region. The first one extends
southwestward from an upper-level low, located north of the Marianas
or near Iwo To, near 23N146E, passing west of the Marianas and exits
the region near 15N130E, passing north of Yap State. The Global
Lightning Detection (GLD) network shows scattered thunderstorms
developing around the upper-level low, with very little thunderstorm
activity along the rest the TUTT axis. The second TUTT has just
entered the region from east of the Date Line and extends south-
southeast from 30N175E, through an upper-level low near 24N178E, and
exits the region, east of the Date Line, near 18N180. the GLD
network only shows a couple of isolated thunderstorms north of the
upper-level low, and very little activity along the rest of the TUTT
axis. Both TUTTS are expected to to drift westward over the next
couple of days. Expecting the greatest thunderstorm activity to
remain along the upper-level low near Iwo To.

...ITCZ...
The ITCZ is redeveloping east and southeast of the Marshall Islands
as satellite imagery and scatterometer data shows southeasterly winds
cross the equator and converging with the northeasterly trade winds
flowing towards the Marshall Islands. This is helping to extend the
numerous showers near Kwajalein, eastward passing north of Majuro and
back towards the Date Line. The western extent of the ITCZ merges
with monsoon trough which extends all the way to Kosrae. Recent model
trends show the ITCZ losing its southeast winds over the next couple
of days, causing the ITCZ to collapse into a series of trade-wind
troughs and leading to an overall decrease of showers near the
Marshall Island in the short-term.

$$

Schank