FZMY50 PGUM 201901

CWFGUM



Coastal Waters Forecast for the Mariana Islands

National Weather Service Tiyan GU

501 AM ChST Mon Sep 21 2026



Marianas Waters out to 40 nautical miles



PMZ150-210915-

501 AM ChST Mon Sep 21 2026



.Synopsis for Marianas Waters...

Light to gentle winds will prevail through midweek, then could

become occasionally moderate from midweek through the second half

of the week. Seas of 4 to 6 feet will slowly subside, dropping a 

foot or so by midweek. Deep southwesterly monsoon flow will keep 

the risk of scattered showers and isolated thunderstorms in the 

forecast for the next several days, with the highest potential at 

night.



$$



PMZ151-152-210915-

Guam Coastal Waters-Rota Coastal Waters-

501 AM ChST Mon Sep 21 2026



.TODAY...Southeast wind 5 to 10 kt. Seas 4 to 6 ft. Wave Detail:

Southwest 3 ft at 8 seconds, north 3 ft at 9 seconds and

northeast 3 ft at 11 seconds. Scattered showers with isolated

thunderstorms. 

.TONIGHT...South wind 5 to 10 kt. Seas around 5 ft. Wave Detail:

Southwest 3 ft at 8 seconds, north 3 ft at 9 seconds, northeast

3 ft at 11 seconds and south 2 ft at 4 seconds. Scattered showers

with isolated thunderstorms. 

.TUESDAY...Southeast wind 5 to 10 kt. Seas around 5 ft. Wave

Detail: Southwest 3 ft at 8 seconds, northeast 3 ft at

10 seconds, southeast 2 ft at 4 seconds and north 2 ft at

9 seconds. Scattered showers with isolated thunderstorms. 

.TUESDAY NIGHT...South wind 10 to 15 kt. Seas around 5 ft. Wave

Detail: Northeast 3 ft at 9 seconds, north 3 ft at 9 seconds and

south 2 ft at 4 seconds. Scattered showers with isolated

thunderstorms. 

.WEDNESDAY THROUGH FRIDAY...West wind 5 to 15 kt. Seas 3 to 5 ft.

Wave Detail: South 3 ft at 4 seconds, north 3 ft at 9 seconds,

northeast 3 ft at 10 seconds and west 2 ft at 8 seconds. A chance

of showers with a slight chance of thunderstorms.  



$$



PMZ153-154-210915-

Tinian Coastal Waters-Saipan Coastal Waters-

501 AM ChST Mon Sep 21 2026



.TODAY...East wind 5 to 10 kt. Seas 4 to 6 ft. Wave Detail: North

3 ft at 9 seconds, northeast 3 ft at 11 seconds, southeast 2 ft

at 4 seconds and southwest 2 ft at 8 seconds. Scattered showers

with isolated thunderstorms. 

.TONIGHT...Southeast wind 10 kt. Seas around 5 ft. Wave Detail:

North 3 ft at 9 seconds, northeast 3 ft at 11 seconds, southeast

2 ft at 4 seconds and southwest 2 ft at 8 seconds. 

.TUESDAY...Southeast wind 10 kt. Seas around 5 ft. Wave Detail:

Northeast 3 ft at 10 seconds, southeast 2 ft at 4 seconds,

southwest 2 ft at 8 seconds and north 2 ft at 9 seconds.

Scattered showers with isolated thunderstorms. 

.TUESDAY NIGHT...Southeast wind 10 kt. Seas 4 to 5 ft. Wave

Detail: Northeast 3 ft at 9 seconds, north 3 ft at 9 seconds and

southeast 2 ft at 4 seconds. Scattered showers with isolated

thunderstorms. 

.WEDNESDAY...Southeast wind 5 to 15 kt. Seas 3 to 5 ft. Wave

Detail: North 3 ft at 9 seconds, northeast 3 ft at 10 seconds and

southeast 2 ft at 4 seconds. A chance of showers with isolated

thunderstorms. 

.THURSDAY AND FRIDAY...Southwest to west wind 5 to 10 kt. Seas 

around 3 ft. Wave Detail: North 3 ft at 8 seconds, southwest 2 ft

at 4 seconds and northeast 2 ft at 9 seconds. A chance of showers.



$$