Impact-based Forecasting and Warning: Weather Ready Nations

High impact hydrometeorological events do not recognize national boundaries. Flash floods, floods, landslides and drought, in particular, give rise to multiple casualties and significant damage to livelihoods and property. In order to significantly reduce losses, communities and individuals need to become more resilient through actions that integrate weather and climate information in decision-making processes.

To provide communities with such integrated weather and climate information, National Hydrological and Meteorological Services (NMHSs) need to develop capacity along the entire service delivery chain. By doing so, they will improve targeted impact-based forecasting, timely dissemination of accurate and easily understandable information, and delivery to the public and other sectors. The adoption of such a robust approach is identified as a high priority in the WMO Guidelines on Multi-hazard Impact-based Forecast and Warning Services (2015, WMO-No 1150) as well as in the Multi-hazard Early Warning Systems: A Checklist (2018), which supports the Sendai Framework for Disaster Risk Reduction 2015-2030 (United Nations, 2015).

Many NMHSs are moving towards a Multi-hazard Impact-based Forecast and Warning Services approach that translates meteorological and hydrological hazards into sector and location-specific impacts and the development of responses to mitigate those impacts. The United States National Weather Service’s Weather-Ready Nation (WRN) programme and the European and United Kingdom’s Impact Based Decision Support Services (IDSS) are examples. Both, as well as the WMO Guidelines, place an increased emphasis on preparation to respond to weather-related events.

It is becoming urgent for more countries to make the transition from focusing only on the accuracy of hazard-based forecasting to also outlining the potential impacts of a forecast – an evolution from “what the weather will be” to “what the weather will do.” To assist countries to do so, the U.S. National Weather Service-International Affairs Office, the U.S. Agency for International Development (USAID)/Office of U.S. Foreign Disaster Assistance (USFDA), University Corporation for Atmospheric Research (UCAR) and the Hydrologic Research Center are partnering with various NMHSs and National Disaster Management Agencies (NDMAs) to transfer the Weather-Ready Nations approach. Barbados, Costa Rica, El Salvador, Guatemala, Indonesia and South Africa are currently in the implementation phase.  

The programme strengthens capacity at NMHS and NDMAs towards better and augmented use of weather, water and climate information to save lives, reduce human suffering and lessen the economic impacts of hydrometeorological hazards.  As a result, participating NMHSs are going beyond producing accurate forecasts and timely warnings to better understanding and anticipating the likely human and economic impacts due to severe weather. There have been notable improvements in communicating their impacts to various stakeholders.

Warning Risk LevelThe targeted information produced by the NHMSs – combined with NDMAs relevant country-specific information such as topography, flood and landslide hazard maps, population demographics and geo-located critical infrastructure and other vulnerability and exposures – aid to rapidly identify populations at risk, exposed assets, physical and social vulnerabilities and to support the quantification of impacts for early action.

Specifically, the goals of the Weather-Ready Nations programme include production of local scale, relevant, impact-based forecasts that can be made into accurate, timely and easily understandable weather, water and climate information services which can, in turn, be easily integrated into decision-making processes. This is achieved through a four-phase approach that defines the What, Where, When and Early Actions that relates to the specific hazard and includes the information in the forecast and messaging.

Close operational cooperation among the NMHSs, NDMAs and other-sector stakeholder agencies, for example agriculture, energy, transportation, health and water resources, is essential for the Weather-Ready Nations to be successful. This requires a high-level commitment from the agencies to work closely together to share data, information, expertise and responsibility. It also requires the development of operational-implementation plans by each of the collaborating agencies with some planned overlap to guide and enable fruitful collaboration. The four phases of the Weather-Ready Nations programme are as outlined below.


Phase One: Developing matrices for impact-based forecasting

Developing Matrices for impact-based forecastingNMHSs and NDMAs work together to understand what information they need to improve decisions that protect lives, livelihoods and property and how they will disseminate reliable and specific forecasts that integrate human, economic, and cultural criteria as the first step. The NMHSs and NDMAs then jointly develop a risk matrix that illustrates the level of impact and the likelihood of occurrence for a specific hazard. Using the matrix, the NMHSs will be able to communicate the probability or likelihood of a potential hazard or multiple hazards and severity of its impacts. NDMAs are then better informed to make effective and timely decisions that factor in potential risk, impacts, costs and benefits.

Both agencies collaborate to identify how the likelihood of forecasted hazards (primary, secondary and tertiary) is associated with the key impacts. The experience of NDMAs in responding to disaster situations provide NMHSs with an understanding of the interdependencies of the infrastructure systems and essential services and by providing geo-spatial data overlays of exposure and vulnerability.  A final component of this phase is the inclusion of advisory or response tables. These tables will provide guidance on what actions will be taken by the NMHSs and NDMAs when a severe weather event is likely to occur. Combining information on the evolving hazard likelihood, possible exposure and vulnerability data through appropriate decision support tools will contribute to the rapid identification of social and environmental risks.

This process is repeated for various sectors such as transportation, health, agricultural communities and community emergency volunteer teams. The matrices and tables are then tailored to the specific needs of each user. By speaking directly to the users and understanding the information they require as well as the information that does not help, NMHSs and the NDMAs improve delivery of tailored forecasts.


Phase Two: Technology and communication tools

The implementation of a multi-hazard impact-based forecasting and early warning approach involves new types of meteorological and hydrological product and warning information as well as new visual and practical presentation of information, including maps, user-specific graphics and weather symbols. This will require either the development of a new web-based display system or the use of existing software that is available to both NMHSs and NDMAs. A web-based tool that incorporates high resolution regional numerical modelling, observations, exposure and vulnerability layers; a tailored impact-based forecast and warning product – together with associated training of users – assists in improving service delivery by developing tailor-made forecasts that specifically address the weather-information needs of various users.

Impact-based forecasting requires that the NMHSs communicate their information so that it supports improved decision-making and planning. There is a growing body of knowledge about how people at risk interpret, understand, and use information in making decisions which NMHSs can use in this process. Incorporating a dissemination platform that links to a geographic information system (GIS)-based impact-based forecasting tool can broaden dissemination of the warning, taking advantage of a wide variety of media sources such as cellular telephony, SMS, radio, television, web page, Facebook, Twitter and WhatsApp. Equally important is both the consistency of the message sent to stakeholders and service delivery before, during, and after a severe weather event. This requires NHMSs to communicate forecasts and NDMAs to disseminate warnings quickly and effectively to as far-reaching an audience as soon as possible.


Phase Three: Development of standard operating procedures

Standard Operating Procedures are intended to help increase and guide early action in case of severe weather events, including drought, flooding, hurricanes and extreme heat/cold, and their impacts such as disease outbreaks. Standard Operating Procedures outline what actions need to be taken by whom and when, once there is the likelihood of a potential or impending severe weather event. This includes the mitigation or prevention of the impacts through disaster preparedness and response.

Standard Operating Procedures provide a structured framework for the initiation of early actions to mitigate the impacts of severe weather with a focus on four key areas:

  • Strengthened, on-time information and analysis of the foreseen impacts of weather events
  • Strengthened coordination that enables partners to implement early action in a timely way
  • Improved early action and preparedness planning at country level.

The target audience for Standard Operating Procedures are NMHSs, NDMAs and other relevant partners at local, regional and national levels.


Phase Four: Training and outreach

A key component in the sustainability of the Weather Ready Nations programme is the capacity-building of the NMHSs, NDMAs and other relevant entities who may be called upon to support core partners before, during or after emergencies. The capacity-building programmes aims to employ a blended learning approach that incorporates the advantages of online courses such as simulation-based training, individual assisted learning and residence training. The training plans will take into consideration the following components:

  • User training for emerging science and technology
  • Communication and collaboration
  • Management through decision support

The training is a critical element in preparing personnel to respond to emergency situations in a team-focused and collaborative environment.

NMHSs and NDMAs play a critical role in providing outreach and education material to establish weather-ready communities that are aware, involved and prepared for the potential impacts of severe weather. Communities and individuals that are educated in understanding the types of severe weather events, their potential impacts, and the importance of community planning for these hazards are in a much stronger position to respond appropriately and help themselves.



United Nations, 2015. Sendai Framework for Disaster Risk Reduction 2015-2030.

World Meteorological Organization, 2015: WMO Guidelines on Multi-hazard Impact-based Forecast and Warning services (WMO-No. 1150); 2018: Multi-hazard Early Warning Systems: A Checklist



The programme was made possible through support provided by the Office of U.S. Foreign Disaster Assistance, U.S. Agency for International Development, under the terms of Award No. AID-OFDA-T-11-00002. The opinions expressed in this publication are those of the authors and do not necessarily reflect the views of the U.S. Agency for International Development.



Rochelle Campbell, Hydrologic Research Center

Daniel Beardsley, U.S. National Weather Service, International Affairs Office

Sezin Tokar, USAID Office of U.S. Foreign Disaster Assistance

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