FZMY50 PGUM 201853

CWFGUM



Coastal Waters Forecast for the Mariana Islands

National Weather Service Tiyan GU

453 AM ChST Sat Mar 21 2026



Marianas Waters out to 40 nautical miles



PMZ150-210845-

453 AM ChST Sat Mar 21 2026



.Synopsis for Marianas Waters...

Elevated northeast to east swell and wind waves, reinforced by 

diminishing long-period north to northeast swell produced by 

distant low pressure systems, will produce seas up to 10 feet 

within the eastern Marianas coastal waters, with 7 to 9 feet 

expected west of the islands. The increase in seas will initially 

occur over eastern Saipan and Tinian waters before spreading to 

Guam and Rota waters tonight, producing conditions hazardous to 

small craft. Combined seas may briefly diminish around Sunday 

night, increasing once more through Monday as the northeast swell 

and wind waves are reinforced by a building trade-wind surge.

Winds will be moderate to fresh out of the northeast to east

through the weekend, possibly becoming fresh to strong Monday.



$$



PMZ153-154-210845-

Tinian Coastal Waters-Saipan Coastal Waters-

453 AM ChST Sat Mar 21 2026



...SMALL CRAFT ADVISORY IN EFFECT THROUGH SUNDAY AFTERNOON...



.TODAY...East wind 15 to 20 kt with occasional gusts to 25 kt. 

Seas 8 to 10 ft. Wave Detail: Northeast 7 ft at 8 seconds, north 

5 ft at 13 seconds, east 4 ft at 6 seconds and northeast 3 ft at 

14 seconds. 

.TONIGHT...Northeast wind 20 kt. Seas 8 to 10 ft. Wave Detail:

Northeast 7 ft at 8 seconds, northeast 5 ft at 6 seconds, north

5 ft at 13 seconds and northeast 3 ft at 14 seconds. 

.SUNDAY...Northeast wind 20 kt with gusts to 30 kt. Seas 8 to

10 ft. Wave Detail: Northeast 7 ft at 8 seconds, northeast 5 ft

at 7 seconds, north 3 ft at 12 seconds and northeast 3 ft at

14 seconds. 

.SUNDAY NIGHT...Northeast wind 20 kt with gusts to 30 kt. Seas

7 to 9 ft. Wave Detail: Northeast 7 ft at 8 seconds, northeast

5 ft at 7 seconds, northeast 3 ft at 12 seconds and north 2 ft at

11 seconds. 

.MONDAY...East wind 20 to 25 kt. Seas 9 to 11 ft. Wave Detail:

Northeast 9 ft at 8 seconds, east 6 ft at 6 seconds and northeast

3 ft at 12 seconds. 

.TUESDAY AND WEDNESDAY...Northeast wind 15 kt. Seas 7 to

9 ft. Wave Detail: East 8 ft at 9 seconds, north 4 ft at

9 seconds, northeast 3 ft at 5 seconds and northeast 2 ft at

11 seconds.  



$$



PMZ151-152-210845-

Guam Coastal Waters-Rota Coastal Waters-

453 AM ChST Sat Mar 21 2026



...SMALL CRAFT ADVISORY IN EFFECT FROM TONIGHT THROUGH SUNDAY

AFTERNOON...



.TODAY...East wind 10 to 20 kt. Seas 7 to 9 ft. Wave Detail:

Northeast 6 ft at 8 seconds, north 5 ft at 13 seconds, east 4 ft 

at 5 seconds and northeast 3 ft at 14 seconds. 

.TONIGHT...Northeast wind 20 kt. Seas 8 to 10 ft. Wave Detail:

Northeast 7 ft at 8 seconds, northeast 5 ft at 6 seconds, north 5

ft at 13 seconds and northeast 3 ft at 14 seconds. 

.SUNDAY...Northeast wind 20 kt. Seas 8 to 10 ft. Wave Detail:

Northeast 6 ft at 8 seconds, northeast 5 ft at 7 seconds, north

3 ft at 12 seconds and northeast 3 ft at 14 seconds. 

.SUNDAY NIGHT...Northeast wind 20 kt with gusts to 30 kt. Seas

7 to 9 ft. Wave Detail: Northeast 6 ft at 8 seconds, northeast

5 ft at 7 seconds, northeast 3 ft at 12 seconds and north 2 ft at

11 seconds. 

.MONDAY...Northeast wind 20 to 25 kt. Seas 8 to 10 ft. Wave 

Detail: Northeast 8 ft at 8 seconds, northeast 6 ft at 6 seconds 

and northeast 3 ft at 12 seconds. 

.TUESDAY...Northeast wind 15 kt. Seas 7 to 9 ft. Wave Detail:

Northeast 7 ft at 9 seconds, north 4 ft at 9 seconds, northeast

3 ft at 5 seconds and northeast 2 ft at 11 seconds.

.WEDNESDAY...Northeast wind 15 kt. Seas 6 to 8 ft. Wave Detail:

Northeast 7 ft at 8 seconds, northeast 3 ft at 5 seconds,

northeast 2 ft at 10 seconds and north 2 ft at 11 seconds.  



$$