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AXPQ20 PGUM 062116

TWDPQ 



Tropical Weather Discussion

National Weather Service Tiyan GU

716 AM ChST Wed Jun 7 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...

Tropical Depression 03W was upgraded to Tropical Storm (TS) Guchol 

overnight. As of 7am, Guchol was centered 470 miles northwest of Yap

and 735 miles west of Guam, moving toward the northwest at 7 mph. 

Overnight scatterometer showed an expanded wind field with tropical 

storm force winds along the northern and eastern sectors. Showers and

thunderstorms on the far southern sector of Guchol continue to sweep

over the main islands of Palau, and to a lesser extent, Yap. 



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...

TS Guchol anchors the eastern extent of the monsoon trough that spans

much of South East Asia.



TUTT... 

The TUTT (Tropical Upper Tropospheric Trough) curves westward from 

beyond the dateline to a pair of TUTT cells, one near Wake Island and

another centered well northeast of Saipan near 19N151E. Divergent 

flow south of the TUTT is enhancing convection across open waters 

southeast and east of the Marianas between 148E and the dateline. 



SURFACE TROUGH AND ATTENDANT CIRCULATION...

A lengthy, north-to-south oriented surface trough is taking shape 

east of the Marianas...east of 150E. The circulation noted in 

yesterday's discussion rests along the southern extent of this

trough. The circulation has edged a bit farther west and is now 

centered halfway between Guam and Chuuk Lagoon near 10N148E. 

Convection continues to flare up along the eastern sector of the 

circulation and along the trough. The prominent TUTT cell to the 

north is likely a large contributor to this convective enhancement. 



...ITCZ...

The ITCZ (Inter-Tropical Convergence Zone) may be best characterized

as a series of trade-wind troughs transiting the region from near

Pohnpei and Kosrae to the Marshalls and farther east to Kiribati. 

Spotty deep convective towers are passing through at times.



...DISCUSSION...

Despite some dry air curling into the western extent of Guchol,

steady intensification is forecast by the JTWC. Latest satellite

imagery shows new convective cells blossoming in the western sector,

which should act to moisten the airmass and encourage core

development. Guchol is forecast to drift northwestward the next few 

days, and could become a typhoon as early as tomorrow (Thursday). 

Showery monsoon weather on the far southern extent of Guchol may 

persist across the main islands of Palau another day or so. The

northward motion of Guchol should pivot the monsoon trough

northeastward. This northeastward pivot should allow a gentle trade-

wind regime to tuck in underneath the monsoon, with gentle trades 

edging into Palau and Yap early next week.



The surface trough and circulation east/southeast of the Marianas

will continue to trek slowly westward. Models hint at a split in this

north-to-south surface trough feature as the far northern extent of

the trough attempts to pinch off a weak circulation near 20N and

separate from the circulation currently between Guam and Chuuk. 

While there is a high likelihood the northern feature struggles to 

retain a LLCC, the southern feature may retain enough vorticity to

stay intact near Palau. If it makes it that far, it could tap into

the established South East Asia monsoon pattern and potentially spin

up near or west of Palau. This is still several days away so will 

monitor closely. The MJO may amplify in our AOR late this month, with

the possibility for additional TC development. Details are fuzzy but

the pattern is ripe early July. 



The ITCZ is still forecast to revive the second half of the week as 

low-level convergence picks up and a slight surge in the trade flow 

occurs. This looks to bring a better chance of showers to central 

and eastern Micronesia south of 12N. Disturbances riding along the 

ITCZ may be enhanced by additional TUTT cell activity to the north. 



$$



Bukunt