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AXPQ20 PGUM 102125

TWDPQ 



Tropical Weather Discussion

National Weather Service Tiyan GU

725 AM ChST Sun Jun 11 2023



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.



...SIGNIFICANT/SPECIAL FEATURES...



TROPICAL CYCLONES...

Typhoon Guchol is currently centered near 22.6N and 131.3E, or about

1085 miles northwest of Guam. Maximum sustained winds have diminished

to 90 mph. Guchol is moving north-northeast at 14 mph. Torrential rain

and isolated thunderstorms are found mainly east of the center as

westerly shear begins to increase, between 21N and 23N from 131E to

133E, or far north of Palau. Monsoon winds south of Guchol will be

discussed in the monsoon trough section.



For more information please refer to bulletins from the Joint

Typhoon Warning Center under WMO header WTPN31 PGTW and from the

National Weather Service under WMO header WTPQ31 PGUM.



...OTHER WEATHER SYSTEMS...



MONSOON TROUGH...

The monsoon trough passes north of Luzon to Typhoon Guchol, Monsoon

winds converging as they flow into Guchol are creating scattered

showers and isolated thunderstorms between 11N and 20N from 134E to

130E and farther west. This is well north of the Republic of Palau,

and well west of the Marianas.



TRADE-WIND TROUGHS...

There are three trade-wind troughs actively producing weather at this

time in Micronesia. The first runs from EQ140E to 8N139E. This trough

is producing scattered showers and a few thunderstorms between 5N and

9N from 136E to 139E, which is east of Koror and includes Ngulu. The

second trough stretches from EQ152E to 10N149E to 15N150E. This trough

is generating scattered showers and isolated thunderstorms between

2N and 14N from 143E to 153E. This includes eastern Yap state, western

Chuuk state, and is east of the Marianas. The third trough cuts from

1N158E to 6N158E. This trough is creating scattered showers and

isolated thunderstorms between the equator and 9N from 154E to 158E.

This includes Pohnpei state just west of Pohnpei island.



TUTT...

The Tropical Upper Tropospheric Trough, or TUTT, extends from an

upper-level low east of the date line through 19N180 to an upper-level

low near 18N167E then heads toward 25N152E. Upper-level divergence

south of the TUTT is sparking scattered showers and isolated

thunderstorms between 1N and 12N from 160E to 180, including most of

the atolls in the Marshall Islands.



Another upper-level low which became separated from the TUTT is near

23N142E. This low is igniting scattered showers and isolated

thunderstorms between 20N and 25N from 145E to 140E, or just north of

the far northern Marianas.



...DISCUSSION...

Typhoon Guchol will turn northeast, having rounded the subtropical

ridge and entered the baroclinic westerlies. It will begin subtropical

transition in 36 hours, but will likely exit Micronesia before that,

perhaps even within the next 24 hours. Other than some ongoing

residual swell generation, Guchol is now a non-event for Micronesia.



The monsoon trough will continue to be dragged northward by Guchol for

the next 24 hours with little change in strength. After that, it will

either move southward and begin to gradually power up a new

disturbance, or it will become involved with the baroclinic westerlies

for a time. At this point it's uncertain exactly what the trough will

do.



The trade-wind troughs will move westward with little change in

strength. The one currently near Ngulu will bring showers to Koror,

Palau in the next day. The one near Chuuk will bring showers to the

Marianas starting in about a day, and Yap in about 2 days. The trough

near Pohnpei will bring showers to Chuuk over the next day.



The TUTT has been getting stronger and growing westward. These trends

are likely to continue as this is currently TUTT season. Look for the

unsettled weather in the Marshalls and Kosrae state to continue, and

it could spread to Pohnpei state.



The upper-level low near 23N142E is moving northward and will likely

exit Micronesia within the next 24 hours.



$$



Stanko