4.1 General
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Statutory Documents - IMO Publications and Documents - Circulars - Maritime Safety Committee - MSC.1/Circular.1310 – Revised Joint IMO/IHO/WMO Manual on Maritime Safety Information (MSI) – (8 June 2009) - Annex - 4 – Navigational Warnings for the World-Wide Navigational Warning Service - 4.1 General

4.1 General

  4.1.1 Navigational warnings are issued in response to SOLAS regulation V/4 and carry information which may have a direct bearing on the safety of life at sea. It is the fundamental nature of navigational warnings that they will often be based on incomplete or unconfirmed information and mariners will need to take this into account when deciding what reliance to place on the information contained therein.

  4.1.2 In order to achieve the necessary impact on the mariner it is essential to present timely and relevant information in a consistent format that is CLEAR, UNAMBIGUOUS and BRIEF. This is ensured by using structured messages in standard formats, as shown in sections 6 and 7 of this manual.

  4.1.3 The resources employed by administrations and the mariner are extremely limited. Thus only information which is vital to the safe conduct of vessels should be transmitted. Notices to Mariners and other means exist for passing less urgent information to ships after they have reached port. Information of a purely administrative nature should never be broadcasted on the regular international navigational warning schedules.

  4.1.4 There are four types of navigational warnings: NAVAREA warnings, Sub-Area warnings, coastal warnings and local warnings. The WWNWS guidance and coordination are involved with only three of them:

  • .1 NAVAREA warnings,

  • .2 Sub-Area warnings, and

  • .3 Coastal warnings.

  4.1.5 Navigational warnings shall remain in force until cancelled by the originating coordinator. Navigational warnings should be broadcast for as long as the information is valid; however, if they are readily available to mariners by other official means, for example in Notices to Mariners, then after a period of six weeks they may no longer be broadcast.

  4.1.6 The minimum information in a navigational warning which a mariner requires is “hazard” and “position”. It is usual, however, to include sufficient extra detail to allow some freedom of action in the vicinity of the hazard. This means that the message should give enough extra data for the mariner to be able to recognize the hazard and assess its effect upon his navigation.

  4.1.7 If known, the duration of the event causing a navigational warning should be given in the text.

  4.1.8 Some of the subjects for navigational warnings listed in paragraph 4.2.2 (e.g., drifting ice, tsunami warnings, negative tidal surges) may also be suitable for promulgation as METAREA forecasts or warnings. In this event, appropriate coordination between the relevant NAVAREA coordinator and METAREA Issuing Service must occur.

Parent topic: 4 – Navigational Warnings for the World-Wide Navigational Warning Service
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