A Hazardous Seas Watch is issued by the National Weather Service of the United States when there is an increased threat of high wave heights and/or wave steepness values reach a certain criteria, but the occurrence, timing, and/or location are still uncertain, though the area of concern is known. The criteria are set by the local forecast offices. It is normally accompanied with strong winds, and occasionally even cyclonic activity. Such tall waves can pose a serious threat to vessels that do not seek shelter, as well as vehicles and property very close to concerned waters.[1]
The following is an example of a Hazardous Seas Watch issued by the National Weather Service office in Medford, Oregon.[2]
316 WHUS76 KMFR 102325MWWMFRURGENT - MARINE WEATHER MESSAGENATIONAL WEATHER SERVICE MEDFORD OR325 PM PST WED DEC 10 2008PZZ356-376-120000-/O.EXT.KMFR.SW.Y.0107.081211T1200Z-081213T0000Z//O.CON.KMFR.SI.Y.0119.081211T1200Z-081212T1200Z//O.NEW.KMFR.GL.A.0027.081213T0000Z-081213T1200Z//O.NEW.KMFR.SE.A.0025.081213T0000Z-081214T1200Z/COASTAL WATERS FROM CAPE BLANCO OR TO PT. ST. GEORGE CA OUT 20 NM-WATERS FROM CAPE BLANCO OR TO PT. ST. GEORGE CA FROM 20 TO 60 NM-325 PM PST WED DEC 10 2008...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS NOW IN EFFECT FROM4 AM THURSDAY TO 4 PM PST FRIDAY......SMALL CRAFT ADVISORY FOR WINDS REMAINS IN EFFECT FROM 4 AMTHURSDAY TO 4 AM PST FRIDAY......GALE WATCH IN EFFECT FROM FRIDAY AFTERNOON THROUGH LATE FRIDAYNIGHT......HAZARDOUS SEAS WATCH IN EFFECT FROM FRIDAY AFTERNOON THROUGHLATE SATURDAY NIGHT...THE NATIONAL WEATHER SERVICE IN MEDFORD HAS ISSUED A GALE WATCH...WHICH IS IN EFFECT FROM FRIDAY AFTERNOON THROUGH LATE FRIDAYNIGHT. A HAZARDOUS SEAS WATCH HAS ALSO BEEN ISSUED. THISHAZARDOUS SEAS WATCH IS IN EFFECT FROM FRIDAY AFTERNOON THROUGHLATE SATURDAY NIGHT. THE SMALL CRAFT ADVISORY FOR HAZARDOUS SEASIS NOW IN EFFECT FROM 4 AM THURSDAY TO 4 PM PST FRIDAY. A SMALLCRAFT ADVISORY FOR WINDS REMAINS IN EFFECT FROM 4 AM THURSDAY TO4 AM PST FRIDAY. COMBINED SEAS WILL BUILD TO 10 TO 11 FEET THURSDAY THROUGH FRIDAY.NORTH WINDS WILL INCREASE TO 15 TO 25 KT THURSDAY AND THURSDAY NIGHT.PRECAUTIONARY/PREPAREDNESS ACTIONS...A SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS MEANS THAT WAVES WILLBE STEEP ENOUGH TO CREATE A POTENTIAL HAZARD TO SMALL CRAFT.SMALL CRAFT CONDITIONS FOR WIND MEANS THAT WIND SPEEDS OF 23 TO33 KNOTS ARE EXPECTED. INEXPERIENCED MARINERS...ESPECIALLY THOSEOPERATING SMALLER VESSELS SHOULD AVOID NAVIGATING IN THESECONDITIONS.A GALE WATCH IS ISSUED WHEN THE RISK OF GALE FORCE WINDS OF 34 TO47 KNOTS HAS SIGNIFICANTLY INCREASED...BUT THE SPECIFIC TIMINGAND/OR LOCATION IS STILL UNCERTAIN. IT IS INTENDED TO PROVIDEADDITIONAL LEAD TIME FOR MARINERS WHO MAY WISH TO CONSIDERALTERING THEIR PLANS.A HAZARDOUS SEAS WATCH IS ISSUED WHEN THE RISK OF HAZARDOUS SEASHAS SIGNIFICANTLY INCREASED...BUT THE SPECIFIC TIMING AND/ORLOCATION IS STILL UNCERTAIN. IT IS INTENDED TO PROVIDEADDITIONAL LEAD TIME FOR MARINERS WHO MAY WISH TO CONSIDERALTERING THEIR PLANS.&&$$