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Historical development of the
World Weather Watch

By James R. Rasmussen
(Director, WMO World Weather Watch Department, 1989–1994)

This article appeared in the January 2003 WMO Bulletin.



Forty years ago, in April 1963, the Fourth World Meteorological Congress approved the concept of the World Weather Watch (WWW) and set the World Meteorological Organization on the journey that dramatically changed and enhanced the development of meteorology and the atmospheric sciences. To commemorate this singular event in the history of WMO and international meteorology in general, it behoves us to sketch the important historical developments leading to those actions of the Congress and then, focusing on the World Weather Watch, to discuss its development and relevance today.

Historical development

A concise summary of the emergence of meteorology as an international science and the gradual application of the science to practical purposes may be found in the first chapter of the volume commemorating the fortieth anniversary of WMO [1].


Proposal of Lt Matthew Fontaine Maury (US Navy),
adopted by the First International Meteorological Conference (Brussels, August 1853)

… all maritime nations should cooperate and make these meteorological observations in such a manner and with such means and implements, that the system might be uniform and the observations made on board the public ship be readily referred to and compared with the observations made on board all other public ships, in whatever part of the world. And, … it becomes not only proper, but politic, that the forms of the abstract log to be used, with the description of the instruments to be employed, the things to be observed, with the manipulation of the instruments and the methods and modes of operation should be the joint work of the principal parties concerned.

Matthew Fontaine Maury


Although dating from 1853, the text in the box on this page is pertinent to the development of international cooperation in meteorology in that it contains the kernel of requirements that have become so basic to our understanding of how meteorology should be done; (a) all nations should cooperate; (b) observations should be standardized; (c) the enterprise should be global; and (d) the parameters measured, the data recording and exchange, and the instruments and methods of observation should follow an agreed plan.

Over the following 20 years the concepts put forward in the maritime community were extended to the emerging national networks of observing stations and led to the First International Meteorological Congress in Vienna, September 1873, where countries with established National Meteorological Services (NMSs) created the International Meteorological Organization (IMO). The Congress dealt with practical matters such as calibration and checking of instruments, time of observation, scales and units, and the mutual exchange of observations by telegraph, etc.—topics that, in one form or another, are still with us today. It also set up permanent machinery to carry on the work. The technical work of IMO was largely carried out by a system of Technical Commissions comprised of groups of experts who addressed issues and proposed solutions and procedures greatly influencing the direction, and accelerating the advancement, of meteorology. Technical issues included expansion of observing networks, instrumentation, standards for observations, codes and symbols and telegraphic and, eventually, wireless communications. With coordination between IMO and the International Telegraphic Bureau, international cooperation on the inter-agency level began.

Following a hiatus imposed by World War I, the pace of activity within the IMO structure resumed with new forces at work such as the application of meteorology to air navigation, the use of radio broadcasts and the invention of improved instruments, i.e. the radiosonde. From 1939 to 1945, war again interrupted the orderly development of the IMO. However, the technological developments, which took place during World War II (e.g. radar, aviation, communications and advances in meteorological science) and the general level of importance that meteorology attained in the emerging world order, re-energized IMO. The World Meteorological Convention was drafted and passed, establishing the intergovernmental World Meteorological Organization in March 1950. WMO assumed the basic technical structure and functions of the IMO and based its continuing effort on the traditions and procedures handed down from the earlier, less formal, non-governmental body. The purposes of WMO, as laid down in the Convention, are a natural extension of the statement adopted almost a century before in Brussels.


Excerpt from the World Meteorological Convention (1953)

The purposes of the World Meteorological Organization shall be:

  • To facilitate worldwide cooperation in the establishment of networks of stations for the making of meteorological observations or other geophysical observations related to meteorology and to promote the establishment and maintenance of meteorological centres charged with the provision of meteorological services;
  • To promote the establishment of systems for the rapid exchange of weather information;
  • To promote standardization of meteorological observations and to ensure the uniform publication of observations and statistics;
  • To further the application of meteorology to aviation, shipping, agriculture and other human activities; and
  • To encourage research and training in meteo-rology and to assist in coordinating the international aspects of such research and training.


The First Congress of WMO initiated a proposal that, after consideration by the United Nations General Assembly, made WMO a Specialized Agency of the United Nations, allowing it to participate in the UN expanded programme of technical assistance to developing countries. It also brought the WMO into partnership with the United Nations and allowed for the UN to call on WMO to assume responsibility for programmes and activities that fell within its terms of reference. Events within the next decade attest to the wisdom and foresight of the delegates to this First Congress. They defined the role and responsibility that WMO should have on the world stage.

The spark

The advent of the Space Age sparked the actions taken by the nations of the world which ultimately led to the World Weather Watch. The launch by the USSR of Sputnik I in October 1957, and Sputnik II in November 1957, followed by the launch by the USA of Explorer I in January 1958, initiated tremendous interest and concern throughout the world, with an intense desire to ensure that this new technology would be used for peaceful purposes. Almost immediately, the WMO Executive Committee (EC) (now Executive Council) anticipated the potential for application of Earth-orbiting artificial satellites to meteorology and appointed a rapporteur on the subject during its 10th session in 1958. The rapporteur (H. Wexler, USA) submitted a report leading the Third World Meteorological Congress in 1959 to pass Resolution 28 Cg-III that set policy regarding meteorological satellites, namely: (a) to encourage the development of meteorological satellites as a means of providing data; and (b) to collaborate on the subject with the UN, other specialized agencies and the scientific community.

Following Congress, EC-XI set up a Panel of Experts On Artificial Satellites with the task of undertaking a continuing review of the possible uses of artificial satellites for meteorological purposes, and to make suggestions as to how WMO could best assist in these activities. The Panel was composed of: V. A. Bugaev (USSR); W. J. Gibbs (WMO Commission for Synoptic Meteorology); G. D. Robinson (WMO Commission for Aerology) and H. Wexler (USA). The first meteorological satellite, Explorer VII, was launched almost immediately afterwards in October 1959, and the first of the TIROS series of satellites was launched in April 1960. The growing interest in the application of satellite data to the various WMO programmes led EC-XII (1960) to request the Panel of Experts on Artificial Satellites to coordinate the work of the Technical Commissions within this field.

Excerpt from President J.F. Kennedy’s address to the UN General Assembly, 25 September 1961

… Scientists have studied the atmosphere for many decades but its problems continue to defy us. … Here, new scientific tools have become available. With modern computers, rockets and satellites, the time is ripe to harness a variety of disciplines for a concerted attack … the atmospheric sciences require worldwide observations and, hence, international cooperation … we shall propose further cooperative efforts between all nations in weather prediction and eventually in weather control. We shall propose, finally, a global system of satellites linking the whole world in telegraph, telephone, radio and television.

Scientists throughout the world, realizing that the emerging technologies (satellites, digital computers, numerical prediction and communications) offered great opportunities for advancement in atmospheric science, set out to articulate just what might be possible in the coming years. For example, the US National Academy of Sciences undertook an evaluation and planning process during the late 1950s that culminated in a report entitled “The atmospheric sciences, 1961-1971”. Here, the title “World Weather Watch” appeared for the first time. It included a worldwide coverage of traditional observations, meteorological satellites, automatic land stations and ocean buoys, balloon systems, soundings from merchant ships and commercial aircraft, a global system of telecommunications, and a network of regional weather service centres [2].

This planning activity, while still under way, fed into the address given by the President of the USA, John F. Kennedy, to the UN General Assembly on 25 September 1961, in which he urged the UN to embark on major new initiatives in weather prediction and satellite-based communications (see box above).

The General Assembly responded, passing Resolution No.1721 (XVI) on 20 December 1961. The Resolution called upon WMO to undertake a comprehensive study of measures:

  • To advance the state of atmospheric science and technology so as to provide greater knowledge of basic physical forces affecting climate and the possibility of large-scale weather modification;
  • To develop existing weather forecasting capabilities and to help Member countries make effective use of such capabilities through regional meteorological centres.

The Secretary-General of WMO, Dr D.A. Davies, immediately enlisted Prof. V. Bugaev (USSR) and Dr H. Wexler (USA) to undertake the requested study. Supported by Dr M.A. Alaka (USA) and the staff of the WMO Secretariat, the First Report on the Advancement of Atmospheric Sciences and Their Application in the Light of Developments in Outer Space [3] was prepared for submission to the United Nations in June 1962. This first report discussed in broad outline the concept, structure and function of the World Weather Watch (see box below).

It called for a marked improvement in global coverage of conventional, as well as satellite, observations and suggested specific network improvements; it called for a dramatic improvement in telecommunications through a worldwide coordinated system; and it suggested that the data-processing system, anchored in the proposed World and Regional Centres, would provide the information required by every nation for its Meteorological Service. Technical assistance to developing Services, including expanded opportunities for education and training, would be required. The report further suggested that the global data and analyses generated by the WWW should be provided to the World Data Centres for climatological and research uses; thus anticipating the important role that the World Weather Watch would ultimately play in climate-related matters.


Extract from the First Report …

The World Weather Watch is intended as a cooperative global meteorological observing and prediction system designed to assist meteorological services of the world to discharge their responsibilities without each service having to perform all the steps needed for this purpose. The inauguration and coordination of this system would be a natural extension of the role that the World Meteorological Organization already plays in the taking and standardization of meteorological observations, the scheduling of meteorological communications, etc. The new activity would be with regard to the orderly creation and dissemination of processed meteorological information, from both conventional and satellite sources and would be based on a system of World Centres and Regional Centres designed to avoid duplication in preparing analyses and prognoses, but still making available to each Meteorological Service the data and background information it requires for carrying out its responsibilities.


The report also listed preliminary research topics that should be addressed through international cooperative efforts to attain the goals laid out in Resolution 1721, and proposed the creation of a WMO Advisory Committee. This committee, with membership from the broad scientific community through organizations such as UNESCO and ICSU, would further address and refine the needs and priorities for research. The preliminary list of research topics included:

  • Problems in the general circulation and heat balance;
  • Problems in numerical weather prediction;
  • Medium- and long-range forecasting;
  • Problems in connection with solar and other external influences on the Earth’s atmosphere and the interaction between the upper and lower atmosphere.

At its seventeenth session in December 1962 the UN General Assembly, in Resolution 1802 (XVII), recommended that “… should develop in greater detail its plan for an expanded programme to strengthen meteorological services and research, placing particular emphasis on the use of meteorological satellites and on the expansion of training and educational opportunities in these fields…”. Resolution 1802 also “… invited the International Council of Scientific Unions … to develop an expanded program me of atmospheric science research which will complement the programmes fostered by the World Meteorological Organization”.

The World Weather Watch

The Fourth World Meteorological Congress, meeting in April 1963, took up the charge contained in UN Resolutions 1721 (XVI) and 1802 (XVII) and set in motion the necessary programme and administrative structures to ensure the Organization could undertake the challenges presented. These included: approval of the World Weather Watch concept as presented in the First Report; setting-up of the WMO Advisory Committee on Atmospheric Research; establishment of a WMO Development Fund in support of the WWW; and establishment of a WWW planning unit in the WMO Secretariat.

The years 1963-1967 were a period of intense planning on both the national and international levels. Technological breakthroughs and the initial resolutions of the UN provided the impetus, but the political, financial and administrative fabric for the budding enterprise needed the constant attention, commitment and energy of the whole meteorological community. Some countries organized national committees or working groups to develop national programmes and to decide what their national contributions to the international effort might be. These national efforts complemented and contributed directly to the work of the Secretariat. Reading the reports of each annual session of the WMO Executive Committee during this period gives a sense of the excitement and plain hard work that permeated the Organization. In addition, the WMO submitted annual sequels to the First Report to the UN [4] which helped keep the development of the WWW visible on the larger international stage. The General Assembly responded again in 1963 through Resolution 1963 (XVIII), reinforcing the earlier resolutions and asking Member States to “cooperate in the establishment of the World Weather Watch”. Such pointed interest from the highest intergovernmental body provided tremendous support and assistance to the permanent representatives with WMO in their efforts to generate national support. The Planning Unit of the Secretariat, working with experts from around the world and the WMO Technical Commissions organized planning meetings that prepared elements of the plan, which were submitted to the Executive Committee. In addition, the World Weather Watch Planning Report Series of publications, more than 25 of which were published in 1967 alone, provided detail, definition and justification for specific components of the emerging Plan.

Two streams of activity were at work concerning the research aspects of the programme. One was the work of the WMO Advisory Committee set up by Fourth Congress and the other was the creation by ICSU/IUGG of the Committee on Atmospheric Research. During the period 1963-1967 a general convergence of both streams was realized with the emergence of the concept of a Global Atmospheric Research Programme conducted by an ICSU/WMO Joint Organizing Committee (JOC). Thus, WMO could concentrate on the formulation of plans and implementation strategies for the operational WWW programme while the joint research pursuit could enlist the broad range of governmental and non-governmental bodies, i.e. national academies of science, in the effort to devise a focused research programme. With regard to the WWW, Global Atmospheric Research Programme (GARP) was to:

  • Recommend to WMO those techniques and procedures developed in GARP activities that might be applied in the operation of WWW;
  • To recommend to WMO the manner in which the scientific requirements of GARP can best be supported by the WWW.

The adoption of the World Weather Watch Plan and Implementation Programme for 1968–1971 by Fifth World Meteorological Congress (Annex to Resolution 16 (Cg-V)) in 1967 was a milestone in the long and rich history of international cooperation in meteorology and in atmospheric science in general. This first plan was intended as the initial step in a process of developing meteorological science and services globally, taking advantage of scientific progress and technological change. The WWW, and the planning process itself, were perceived as dynamic—flexible enough to adapt to changing conditions—and open to technological and scientific advances.

It focused on the following basic concepts:

  • The primary purpose of the WWW was to ensure that all WMO Members obtained the meteorological information they required for both operational work and for research. (In principle, all a Member needed to participate in the WWW was a teletype machine!);
  • The WWW was to be a worldwide system composed of national facilities and services provided by individual Members, coordinated, and in some cases supported, by WMO and other international organizations;
  • The WWW was to be used for peaceful purposes only;
  • The WWW was to be used to stimulate and facilitate research;
  • The WWW would require an adequate programme of education and training;
  • The information required by Members would include both observations and processed data exchanged in a timely and coordinated fashion and accessible in convenient forms;
  • Maximum use was to be made of existing facilities and arrangements in all fields of activity.

The essential elements of the WWW as described in the Plan were:

  • Observational networks and other facilities—the Global Observing System (GOS);
  • The meteorological centres and the arrangements for processing observational data—the Global Data-processing System (GDPS);
  • The telecommunications facilities and arrangements for the rapid exchange of information—the Global Telecommunication System (GTS);
  • The research programme;
  • Education and training.


Excerpt from the intervention of Dr Robert White during the Fifth World Meteorological Congress

Dr Robert WhiteThe World Meteorological Organization is at a crossroads. The action that we take on the financial matters before us will, in large measure, determine which direction we take. Down one road lies the realization of the promise that our modern technology opens up. Down the other lies a continuation of the past. …. At this Congress the time for action has come. …"


The proceedings of Fifth Congress provide insight into the magnitude of the programmatic and financial commitments that Members were undertaking, both in their national programmes and in support to WMO and its Secretariat. The leadership of Dr Robert White, Permanent Representative of the USA, is especially noteworthy—a quote from his intervention after the Secretary-General presented the budget proposals for the fifth financial period illustrates his strong position and forcefulness (see box).

The machinery for governance and orderly development of the WWW rested with the WMO Technical Regulations including the annexes and the manuals on the GOS, GDPS and GTS. The organizational entity that would undertake the bulk of the work to develop the technical details of the programme and implement the internationally agreed elements was the WMO Commission for Basic Systems (CBS), which, prior to 1971, was named the Commission for Synoptic Meteorology. CBS accomplished its task through working groups that focused on each of the three main components and an Advisory Working Group that coordinated the complex and interrelated activities and responded to requirements from other technical commissions and programmes. The WMO regional associations dealt with the regional implementation of the WWW Programme.

Implementation and evolution of the World Weather Watch

In the years and decades since 1963, significant developments have occurred in the atmospheric and oceanic sciences and in the technologies related to these disciplines, that have had an impact on the WWW and, to some degree at least, the WWW has in turn contributed to the developments themselves. Progress in implementing the original Plan and the constantly emerging technological opportunities required that an updated Plan and Implementation Programme be agreed at each succeeding Congress until 1983, when this activity was assumed by the WMO long-term planning process.

In a very real sense, the WWW will always be incomplete and unfinished. Considering that the WWW is comprised of the facilities and operations of the NMSs of all the 185 Members of WMO, each with its own unique requirements for meteorological services, and each with different levels of technical and financial capability, it is not surprising that there have been frustrations and shortfalls in reaching the goals as laid down in the various editions of the Plan. From 1967 onward, the reports of Congress, the Executive Council, the regional associations and the technical commissions, especially CBS, attest to these “growing pains”. Opportunities arising from technological progress (e.g. global communications and computer capacity and speed) often cannot be implemented quickly enough throughout the global system so that all Members benefit.

The technical cooperation programmes, while tremendously beneficial to many developing services, simply have not been able to satisfy all needs. The requirements for education and training of staff in the Meteorological Services of the developing countries are consistently only partially met—and the rate of turnover of technically trained staff is a persistent problem for many Meteorological Services. In the early 1980s, CBS undertook the Integrated Systems Study in order to assess the overall development of the WWW and to prioritize its implementation in such a way that the impact on the overall integrated system was optimized. The WWW Data Management component of the Basic System was developed to bring to bear modern ideas such as distributed databases and the exchange of software among Members. These steps, among others, have helped make progress in fulfilling the Plan in recent years.

The role played by research institutions and programmes in the development of the WWW is a topic that deserves a separate article. The GARP had the greatest influence through a focused effort to develop the science and technology for application to numerical weather prediction, and for designing and mounting field experiments, focusing on specific meteorological problems, often using new and innovative observing systems. The GARP Atlantic Tropical Experiment (GATE) was fielded in 1974 with the objectives of providing the data resources to understand the effect of small tropical weather systems on the larger-scale circulation. Five years later in 1979 the First GARP Global Experiment (FGGE) succeeded in the deployment of special observing capabilities that, in the aggregate, approached the global coverage dreamed of by the planners of the WWW back in the early and mid-1960s. The integrated observing programme included:

  • An augmented WWW network of surface and upper-air stations both on land and from ships;
  • A constellation of five geostationary satellites and four polar-orbiting satellites providing truly global coverage of the windfield derived from cloud-motion observations and vertical profiles of temperature;
  • A system of super-pressure balloons circulating at high altitude in the tropical belt and providing real-time data through a satellite-based communications and location finding system (ARGOS);
  • Aircraft observations from specially equipped airliners and a dedicated fleet of reconnaissance aircraft deploying dropsondes;
  • The deployment of drifting buoys over the vast reaches of the Southern Ocean using the ARGOS system for communications and location;
  • A flotilla of research vessels equipped to take high-resolution vertical profiles of the windfield in the tropics.

In addition, regional programmes to study the monsoon circulation systems in Asia (MONEX) and West Africa (WAMEX) were fielded during the same time as FGGE in order to take advantage of the intense global observational resource and, in turn, to contribute to the global effort with enhanced observations from their respective regions.

These research programmes were possible because of the worldwide infrastructure provided by the WWW system of observations, communications and data processing. Many of the systems and technologies developed and deployed during the experiments have become integral parts of the operational WWW itself. The vision of the early planners for a complementary partnership between the atmospheric science community and the operational meteorology community has been one of the outstanding results of the Programme. It continues today.

Over the last two decades there has been an upsurge in commercial activity in the provision of meteorological services. This commercial sector includes both non-governmental firms, with a potentially global reach, and components of some NMSs. Issues threatening the WWW tradition of free and unrestricted international exchange of data and products arose in the context of this commercial activity. After careful study, Twelfth World Meteorological Congress passed Resolution 40 (Cg XII) that laid down WMO policy and practice for the exchange of data and products and set up guidelines on relationships between NMSs and the commercial sector. The future development of the WWW depends on the effective implementation of the data-exchange policy.

It is impossible in a short article to cover adequately the important milestones, accomplishments and challenges that the WWW has experienced over the last 40 years. A brief summary follows of what, in the author’s opinion, are the most significant in the context of the three WWW components.

The Global Observing System (GOS)

Space-based systems

As discussed above, meteorological satellites have always been one of the principal elements in the concept and implementation of the WWW. The development of the automatic picture transmission (APT) system in the early 1960s provided the opportunity for all NMSs to have direct access to real-time satellite imagery for their forecast and analysis applications. Until high-speed communications capabilities were available to carry a broader range of satellite data, the APT system ensured that all NMSs could have access to real-time information from meteorological satellites. The APT capability is an outstanding example of the application of the basic concepts of the WWW.

  Meteorological satellites are providing increasingly significant inputs to the World Weather Watch.

The progressive development of the space-based system from the rudimentary polar-orbiting satellites at the beginning of the WWW to the current operational configuration of three to four polar orbiting systems and five to six satellites in geostationary orbit has been perhaps the single greatest accomplishment in our ability to observe the global atmosphere and ocean. The assessment is based not only on the number of satellites but also on the constantly advancing technology in the sensor systems and sophistication in operational capability. The satellite operators have closely coordinated their plans with the WWW and the provision of satellite data into the WWW system has been a model of international response to user requirements. Other than in the application of visible and infrared imagery on weather analysis, the actual impact of satellite data on global-, regional- and local-scale numerical analyses has been slow to materialize. In the 1990s, the major numerical prediction centres developed ways to assimilate satellite observed radiance values into their analysis schemes and this has begun to bring the value of satellite data up to the level that has long been anticipated.

Satellite operators are currently seeking ways to ensure that data from experimental systems are available to users following WWW protocols. As has been demonstrated in the GARP experiments, the application of new data in operational settings is often the best test of its lasting value.

Surface-based observing systems

Upper-air observing

A persistent problem facing the WWW has been the establishment and maintenance of the global radiosonde network. The evolution of systems from those based on radar to those based on navigational aid radio beacons, to the current systems utilizing the Global Positioning System, has resulted in continued improvement in data quality and ease of operation. However, the high cost of equipment and expendables has made it impossible to attain the global network envisaged. Some compensation has been attained through the utilization of vertically pointing radar systems (profilers); through utilizing modern avionics systems on commercial airliners—providing data on assent and decent as well as at flight level; and from the improved sounding capability from satellites and the continued deployment of shipboard upper-air systems. The in situ upper-air observing network will continue to be a major issue facing the WWW. Research programmes employing drone aircraft and a variety of balloon-borne systems show some promise in helping to attain the density and coverage required.

Surface networks

Two major advances have characterized the evolution of meteorological observations at the Earth’s surface. The first is the development of automatic weather- observing technologies that have permitted the more efficient use of personnel and allowed for the deployment of observing systems in more remote locations. The second advance has been the major improvement in observations over the ocean. The cooperative arrangements between the IOC and the WMO/WWW that led to the implementation of the IGOSS system was an early step in fulfilling the requirement for data coverage over the ocean. The development and deployment of drifting and moored buoy systems throughout the world’s oceans, with data acquisition and location provided by satellite-based systems, have dramatically improved the data coverage.

Global Telecommunication System (GTS)

Historically, the GTS functioned on three levels: (a) the Main Telecommunications Network—a high-speed circuit that connected world centres with branches to regional hubs so that the regions were effectively connected to the global system; (b) Regional Meteorological Telecommunications Networks; and (c) National Meteorological Telecommunication Networks. Over the years, the plan for the GTS has progressed from the original “store-and-forward” system with its mix of automatic and manned facilities requiring an intense management effort and which was subject to outages and failures, especially at the regional level; to a system which might be described as “mixed”, with some national and regional components utilizing “two-way point-to-multi-point” two-way satellite-based systems, while others operate in the traditional mode. Some particularly difficult circuits have utilized the Internet as an option. The great strength of the WWW GTS is that it allows the telecommunication connections between Members and within and between Regions to be determined by the Members concerned as long as international exchange commitments and protocols, as set down in the WMO Technical Regulations, are met. The GTS is constantly under review within CBS and planning for upgrading the global system to take advantage of the revolutionary changes in communications technology, while ensuring every Member receives the meteorological information it requires, is a high priority.

Global Data-processing System (GDPS)

The original WWW Plan focused on the establishment of three World Meteorological Centres (WMCs) and anticipated a number of Regional Centres (RMCs) to eventually emerge. The operational concept was for the WMCs to undertake the task of assembling data, information such as output fields from global numerical prediction models, and their interpretation for use by the various RMCs, which, in turn, would add a level of more detail in order to support the National Meteorological Centres (NMCs) in their service provision responsibilities. Over the years, the research contributions from major field programmes such as FGGE and the development of major modelling centres (such as the European Centre fore Medium-Range Weather Forecasts, the US Geophysical Fluid Dynamics Laboratory and National Center for Atmospheric Research, and major research programmes at academic and research institutions around the world) did much to expand the definition and role of the WWW GDPS. Numerical weather prediction on the continental and subregional to mesoscales became operational. The structure of the GDPS evolved and currently there are some 25 Regional Specialized Meteorological Centres (RSMCs) with geographic specialization. These centres run a suite of models and analyses particularly designed and tuned to provide forecast guidance for a particular topographical or ocean area, often using data sources of a local or regional nature, e.g. radar data. In addition, there are six RSMCs with tropical cyclone prediction responsibility and eight RSMCs with transport modelling responsibilities. The latter category has regional responsibility to provide atmospheric transport model products for environmental emergency response in the case of a nuclear accident, volcanic eruption or other emergency. In addition, several designated RSMCs provide medium-range weather forecasts, drought monitoring and prediction and extended- and long-range forecasts. Some 32 other NMCs possess some level of numerical prediction capability, ranging from full global models to limited-area models to more high-resolution meso-scale models.

Remarkable advances in the techniques for data assimilation into models and in the procedures for processing model output, such as ensemble prediction schemes, that allow the best possible forecast outcome, to be objectively attained, continue to increase the accuracy and usefulness of numerical prediction products.

The continued improvement of both accuracy and lead time of weather forecasts attests to the progress made in implementing the WWW system as a whole, as well as in the development of the atmospheric sciences in general and numerical prediction in particular. Five-day forecasts today have better accuracy than two-day forecasts did in the 1970s and the prediction of extreme events, such as the occurrence, intensity and track of tropical cyclones, have also shown significant improvement.

The systematic archiving of meteorological data over the 40-year history of the WWW has allowed research-focused institutions, the World Meteorological Centres and some RSMCs to undertake what is referred to as “re-analysis”. Here, the latest and most sophisticated numerical analysis techniques are applied to the whole historical data record, yielding a physically consistent set of analyses covering the whole period. This powerful tool finds application in general circulation studies, research in long-term weather prediction and in climate studies.


Forty years ago, the World Weather Watch was conceived as an integrated global system of meteorological observations, telecommunications and data-processing facilities and supporting activities linking all countries of the world in order to assist the NMSs in their task of providing services to their governments and populations. It was to be composed of national facilities and services owned and operated by the NMSs of the individual Members of WMO. It would be coordinated and regulated through the WMO as would the associated technical cooperation and education and training programmes. The operation of the enterprise was to be based on the fundamental concept that each of the Members of WMO (185 at the end of 2002) undertakes, according to its means, to meet certain responsibilities in the agreed global scheme so that all countries might benefit from the consolidated efforts.

The challenge laid down 40 years ago has resulted in a unique success story of international cooperation and opportunity. The basic system of the WWW has become in many ways the “core” operational facility, not only for weather forecasting, but also for all WMO programmes, as well as many international programmes of other agencies. Understanding climate and climate change, natural disaster reduction and response, and environmental protection are but three of a growing list of these broader programmes. We can expect the next years to be of even faster technological advancement, and we can also expect new requirements to be placed on the basic systems by the more integrated Earth science programmes. The flexible, evolving system that was conceived originally continues to adjust and accommodate these new demands today. It is hoped that future WMO Congresses will have the foresight and vision equal to those exhibited 40 years ago—enabling the WMO to provide the stimulation, leadership and cooperation that have been the hallmark of the World Weather Watch.

[1] WMO, 1990; Sir Arthur Davies (Ed.). Forty Years of Progress and Achievement, A Historical Review of WMO.
[2] WMO, 1966. Severre Pettersen, WWW Planning Report No. 5. Research Aspects of the World Weather Watch.
[3] WMO, 1962. First Report of the WMO on the Advancement of Atmospheric Sciences and Their Application in the Light of Developments in Outer Space.
[4] WMO, 1963. Second Report of the WMO on the Advancement of Atmospheric Sciences and Their Application in the Light of Developments in Outer Space.
WMO, 1964. Third Report of the WMO on the Advancement of Atmospheric Sciences and Their Application in the Light of Developments in Outer Space.
WMO, 1965. Fourth Report of the WMO on the Advancement of Atmospheric Sciences and Their Application in the Light of Developments in Outer Space, WWW—Phase I.
WMO, 1966. Fifth Report of the WMO on the Advancement of Atmospheric Sciences and Their Application in the Light of Developments in Outer Space, WWW—Phase II.







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