426
AXPQ20 PGUM 260118
TWDPQ

Tropical Weather Discussion
National Weather Service Tiyan GU
1118 AM ChST Thu Sep 26 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`s Invest 95W has continued to move north-northwest, and is still
east of the Mariana Islands. Visible satellite imagery shows a exposed
low-level circulation north-northeast of Saipan and jut east of
Anatahan near 16N146E. Meanwhile the latest CIMSS`s satellite
analysis shows a broad area of vorticity within the 850-500mb layer,
to the east-southeast of this low-level circulation near 15N148E. The
heaviest showers and thunderstorms are near the location of the mid-
level vorticity, and scatterometer data shows 15-25 kt along the
eastern and northern edge of the overall vorticity feature with gusty
winds near showers and thunderstorms. The latest satellite loop over
the past 3 hours show a slow northwest motion overall of 95W, with
the low-level circulation starting to slow its motion as it starts to
make a counter-clockwise motion around the main mid-level vorticity.
The Joint Typhoon Warning Center (JTWC) has issued a Tropical Cyclone
Formation Alert (TCFA) for 95W early this morning stating it has a
high potential for development into a tropical depression and this
is likely to occur within 24 hours. 95W is expected to pass north of
Saipan and through the far northern islands of the Marianas, before
passing into the Philippine Sea over the next few days. Heavy showers
and thunderstorms along with gusty winds near the heavier showers
will be possible near and north of Saipan over the next few days as
95W slowly moves through the far northern Mariana Islands.

For additional information the TCFA for Invest 95W, please see the
bulletin issued by JTWC under the WMO header WTPN21 PGTW.

...OTHER WEATHER SYSTEMS...

TRADE-WIND TROUGHS AND SURFACE TROUGHS...
A broad, east to west trough extends from Invest 95W, through the
Marianas and continuing west-southwest, passing through a weak
circulation well north of Yap State and west of the Marianas, near
14N138E and ending near the Philippines, exiting the region beyond
13N130E. This trough does not extend all the way to southeast Asia,
as it broken by a weak ridge, so it not a monsoon trough, but it is
inducing west to southwest winds across the Republic of Palau, Yap
State, and the Marianas near and south of Saipan. Satellite imagery
shows some scattered to numerous showers and isolated thunderstorms
both 95W and the weak circulation north of Yap State, with showers
becoming more spotty to low-end scattered at Yap Proper and Palau.
This trough will slowly lift northwest as it is pulled by 95W and may
eventually become a true monsoon trough if it connects to southeast
Asia. As the trough lifts northwest, easterly winds will slowly move
back into the Marianas, Yap, and Palau this weekend or early next
week.

A couple of trade-wind troughs can be seen over eastern and central
Micronesia, the first near Chuuk Lagoon and it extends northeast to
just northwest of Pohnpei. The second trough extends across Majuro
and northeast towards 9N and the Date Line, with a very broad
circulation embedded within this trough near 8N176E, east of the
Marshall Islands. Showers are fairly spotty to scattered along the
troughs and the Global Lightning Detection (GLD) network shows very
little thunderstorm activity along the troughs. As these troughs
drift westward, expect some periods of scattered showers as these
troughs near the islands of central and eastern Micronesia, with the
broad circulation east of Marshall Islands expected to slowly
dissipate and open back into the main trough.


TUTT...
The TUTT now extends along the northern edge of the region entering
the region near 25N154E from TUTT cell, and extending west-southwest
passing north of the Marianas and ending near 16N130E, northwest of
the circulation west of the Marianas. The only notable convective
activity is southeast of of the TUTT cell where the upper-level
divergence is the greatest, where isolated to scattered showers and
thunderstorms are developing to the west of Wake Island, near 19N160E.
The TUTT will slowly drift west-northwest, remaining along the
northern edge of the region, with thunderstorms and the TUTT cell
expected to move towards or north of the far northern islands of the
Marianas.

$$

Schank