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The international scheme by which ships plying the various oceans and seas of the world are recruited by National Meteorological Services (NMSs) for taking and transmitting meteorological observations is called the World Meteorological Organization (WMO) Voluntary Observing Ships' (VOS) scheme. The forerunner of the scheme dates back as far as 1853, the year in which delegates of ten maritime countries came together at a conference in Brussels, on the initiative of Matthew F. Maury, then director of the United States Navy Hydrographic Office, to discuss his proposal for the establishment of a uniform system for the collection of meteorological and oceanographical data from the oceans and the use of these data for the benefit of shipping in return.

The conference accepted his proposal and adopted a standard form of ship's log and a set of standard instructions for the necessary observations.

From the very beginning, ships' meteorological observations were recognized as being essential for the provision of safety related meteorological services for ships at sea, as well as for climatological purposes.

The Situation Today:

At the present time, the contribution which VOS meteorological reports make to operational meteorology, to marine meteorological services and to global climate studies is unique and irreplaceable. During the past few decades, the increasing recognition of the role of the oceans in the global climate system has placed even greater emphasis on the importance of marine meteorological and oceanographical observing systems.

One of the major continuing problems facing meteorology is the scarcity of data from vast areas of the world's oceans (the so-called 'data sparse areas') in support of basic weather forecasting, the provision of marine meteorological and oceanographic services, and climate analysis and research.

While the new generation of meteorological satellites help to overcome these problems, data from more conventional platforms, in particular the voluntary observing ships, remain essential. These ship observations provide ground truth for the satellite observations, important information which the satellites cannot observe, essential contributions to the data input for the numerical weather prediction (NWP) models, and to provide realtime reports which can be used immediately in services for the mariner. In addition to their use in NWP, reports from ships at sea are also used operationally, even more directly, in the preparation of forecasts and warnings, including those for the Global Maritime Distress and Safety System (GMDSS), and issued specifically for the mariner.

Thus, without VOS observations, reliable and timely services for mariners cannot be provided.

The VOS Fleet Size:

A peak in total VOS was reached in 1984/85 when about 7700 ships worldwide were on the WMO VOS Fleet List. Since then there has been an irregular but marked decline and in June 1994, the Fleet strength had dropped to about 7200 ships. These numbers have continued to decline and are currently estimated at only about 4000 ships worldwide. As might be expected, realtime reports from the VOS are heavily concentrated along the major shipping routes, primarily in the North Atlantic and North Pacific Oceans. The chart below shows the data sparse areas in all the southern hemisphere oceans. While this situation certainly reflects the relatively small numbers of ships sailing in these waters, it also makes it more essential that ships sailing in these areas should be part of the VOS and thus contribute to the global observing program and consequent enhancement of the forecast and warning services to the mariner. Of course, as VOS reports are part of a global data capture program, their reports are of value from all the oceans and seas of the world, and even the well frequented North Atlantic and North Pacific Oceans require more observational data.

Data sparse areas in the southern hemisphere oceans


What are the charges to be part of the VOS scheme?

THERE ARE NO CHARGES TO THE SHIP OR TO THE OPERATOR. The tested marine meteorological instruments necessary to undertake weather observing at sea are usually supplied free of charge to the ship, installed by a professional from the NMS, usually a trained Port Meteorological Officer (PMO), who will provide advice on the technique of observing at sea, explain the use of the WMO SHIP code and offer guidance on the transmission of the observations from the ship to shore, using the ship's own satcom or terrestrial communications equipment.

THERE ARE NO CHARGES TO THE SHIP FOR THE TRANSMISSION OF VOS WEATHER REPORTS. After recruitment into the VOS program, the meteorological instruments will be regularly serviced, without charge to the ship or ship owner, by an official of either the 'recruiting NMS' or from the worldwide network of WMO Members who operate the international VOS program.

How can you become involved?

If a Shipping Administrator:
  1. Be aware that ships' meteorological reports can make a significant contribution to safety of life and navigation through better quality forecasts and warnings.
  2. Ensure that your ship operators are aware of the WMO VOS scheme and encourage their participation.
If a Ship Operator:
  1. Contact your NMS, or a local Port Meteorological Officer, nominate your ships for recruitment into the WMO VOS scheme.


Only YOU know the weather at your position. Report it!

U.S. Dept. of Commerce
National Oceanic and Atmospheric Administration
National Weather Service
Voluntary Observing Ship Program
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