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AXPQ20 PGUM 091028 AAA
TWDPQ

Tropical Weather Discussion...UPDATED
National Weather Service Tiyan GU
828 PM ChST Sat Nov 9 2024

Updated to add information on the development of Tropical Depression
Toraji and upgrade Man-yi (25W) from tropical depression to tropical
storm.

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 CYCLONES...
The Joint Typhoon Warning Center`s (JTWC) has upgrade Tropical
Depression 25W to Tropical Storm Man-yi. Man-yi is northwest of the
Marshall Islands near 14.78N 158.3E, roughly halfway between Pohnpei
and Wake Island. Himawari infrared satellite imagery shows a broad
region of moderate to deep convection consolidating about the
circulation center. Bands of numerous showers and isolated
thunderstorms extend far north and northeast to the south of Wake
Island. Man-yi continues to move northwest over the next day or so
as it consolidates and strengthens, possibly reaching strong tropical
storm strength (maximum sustained winds > 49 kts) by Monday as it
passes Pohnpei far to the north. However, recent model trends point
to a weakening and loss of structure as Man-yi continues on westward
toward the northern Marianas. Man-yi will potentially pass near
Saipan Tuesday night into Wednesday as a tropical depression,
bringing locally heavy showers and gusty winds.

The Joint Typhoon Warning Center has upgraded 92W to Tropical
Depression Toraji (26W) this evening with winds around 30 kt (35
mph). Toraji is located well within the Philippine Sea, well
northwest of Yap and Palau, centered near 14.6N 130.9E, and is
expected to move northwest towards the northern Philippines and
exit our region.

For more information, please refer to bulletins from the Joint
Typhoon Warning Center under WMO headers WTPN32 PGTW and WTPN33 PGTW
and from the National Weather Service under WMO headers WTPQ32 PGUM
and WTPQ33 PGUM.

TROPICAL AND MONSOON DISTURBANCES...
Tropical disturbance, JTWC`s Invest 94W, is located
west-south west of Chuuk near 6.5N 149.5E, having moved slowly
northwest since yesterday. Heavy showers and thunderstorms are
disorganized about the elongated center of circulation, extending in
bands north, east, and south of the center, with the heaviest showers
mainly focused along the eastern flank over the Nomoi Islands
extending northwest over Chuuk Proper. Surface observations at Chuuk
have reported wind gusts to around 22 knots associated with showers.
94W looks to remain disorganized as it moves northwest through Chuuk
State tonight, continuing to move northwest. Model trends keep 94W
on a northwest trajectory moving roughly "in sync" with TS Man-yi
(25W), passing between Yap and Guam on Monday potentially as a
tropical depression, with model disagreement regarding wind strength
and overall organization.

For more information on Invest 94W, see bulletins issued by the
JTWC under WMO header ABPW10

...OTHER WEATHER SYSTEMS...

TRADE-WIND AND SURFACE TROUGHS...
A broad surface trough extends northwest over Pohnpei State from
Invest 94W, passing over Pohnpei Proper before extending north
through TD 25W, continuing onward to the west of Wake Island near
20N163E. Scattered showers near Pohnpei extend northward into an
area of numerous showers focused about 25W, spreading northward
to around 19N and eastward across the southern periphery of Wake
Island`s coastal waters. This trough will shift west to northwest
with the movement of TD 25W and 94W, breaking apart during the
latter half of the week as these systems move west into the
Philippine Sea.

A shallow trade-wind trough extends southeast from the south of
Wake Island near 17N166E, along the leading edge of a trade-wind
surge, mentioned in the section below. This trough passes east of
the RMI`s Ratak (sunrise) Chain and extends southeast into an
Intertropical Convergence Zone (ITCZ) to the east of Majuro,
mentioned in the relevant section below. Scattered showers and a
few thunderstorms are seen along this trough axis, focused mainly
east of Majuro within a portion of the ITCZ close to the Date
Line. Slightly further west, a weak trade-wind trough extends
southeast along the RMI`s Ralik (sunset) Chain, from near
Ailinglaplap Atoll to around EQ175E. Scattered showers are seen
along this trough axis to the west and south of Majuro. These
features will shift west over the next few day or so, diminishing
by Monday as TD 25W moves northwest away from the area.

TRADE-WIND SURGE...
Scatterometry shows an area of moderate to strong trades north and
northeast of the Marshall Islands across a broad area between 10N
and 24N, from roughly 170E to beyond 180. This moderate trade
wind surge has shrunk closer to the Date Line since yesterday.
Scattered showers and a few thunderstorms are seen within this
broad region associated with a tightened pressure gradient between
TD 25W and the subtropical ridge to the north. This continues
over the next few days before weakening by early next week as the
pressure gradient relaxes over the area.

ITCZ...
An ITCZ fragment extends westward into the AOR near 6N180
and continues to around 6N176E to the east of Majuro Atoll.
Scattered showers and isolated thunderstorms extend west along
this ITCZ fragment and northwest along a trade-wind trough east of
the Marshall Islands, mentioned above. The ITCZ will extend west
across the RMI over the next day or so, becoming ill-defined as a
fragment shifts west across eastern Micronesia as a surface trough
through the midweek.

$$

DeCou/Schank