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AXPQ20 PGUM 042032

TWDPQ 



Tropical Weather Discussion

National Weather Service Tiyan GU

632 AM ChST Mon Jun 5 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 AND MONSOON DISTURBANCES...

A developing circulation, given the designation of Invest 98W by

the Joint Typhoon Warning Center (JTWC), is located near 11.4N

137.4E. This system has a medium chance of development, and is

currently located just north of Yap. Most of the heavier shower

and thunderstorm activity is displaced well to its east, with a

few isolated showers and thunderstorms developing in a southerly 

to southwesterly monsoon flow.



...OTHER WEATHER SYSTEMS...



TRADE-WIND TROUGHS...

A surface trough extends from EQ150E through Chuuk before ending

near 13N154E. Just a few showers and thunderstorms are developing

east of this feature. Another trough is located between Kwajalein

and Majuro, with yet a third such feature just west of the

Dateline/east of Majuro. All of these features are located within

a strengthening Inter-Tropical Convergence Zone (ITCZ), with

scattered convection noted from Kosrae and at points east and

northeast of there.



...ITCZ...

A strengthening ITCZ stretches from near Pohnpei to well east of 

the dateline, with fairly expansive convection from Kosrae 

eastward. This convection is found mainly between 4N and 9N, with

cloud top temperatures pushing -80 deg. C. Thus, pockets of 

heavier rainfall are likely embedded under the cooler cloud tops.



...DISCUSSION...

Invest 98W is forecast to strengthen over the next few days, and

it wouldn't be surprising if the system is assigned a TCFA

(Tropical Cyclone Formation Alert) in the next 24 hours or so. 98W

is forecast by the GFS to gradually develop into a tropical storm,

and then a typhoon, as it heads on a north to northwest track 

over the open Philippine Sea. The ECMWF, is weaker and slower in 

it's development (as usual), taking it on a more westerly track. 

In either case, it won't affect any land masses in the short to 

medium range (up to 5 days), it'll be of little impact anywhere.



Attention then turns to the strengthening ITCZ, which stretches to

near 150W, with embedded troughs within it. This feature is fairly

robust, and one of the better (if not the best) signature we've 

seen in the ITCZ this year. Aside from some brief periods of 

locally heavy rainfall as it crosses the Marshall Islands and 

into the Federated States of Micronesia over the next week, the 

question and key feature will be to see if the ITCZ maintains 

itself, as the Madden-Julian Oscillation (MJO) may come into a 

more favorable phase towards the end of the month, which could 

increase tropical cyclone formation potential, especially if the 

ITCZ remains coherent and active.



$$



Doll