Predictability of a disaster is the key to understand its nature and thereby to assess the chances of its occurrence and the fury of the event. Predictability is an attribute really applicable to natural disasters. For man-made disasters, it is the human error or mechanical fault or organizational failure that is responsible. Therefore, there is no concept of predictability as such for man-made disasters. Mock drills, regular inspections and updating of precautionary measures take the place of predictability, forecasting and warning in case of man-made disasters.
For natural disasters that have a fair amount of inherent predictability, forecasting is the next step in disaster management. Forecasting has to be based on sound scientific principles and operationally proven techniques. It has to be done by authorized agency or individual who, besides being competent, responsible and accountable, is conscious of the end-use of the forecast and the dependence of the success of disaster management on the forecast. In order to be effective, the forecast has to be clearly forded and it should be transmitted quickly to the user.
Once a forecast is available regarding an anticipated disaster event, it has to be converted quickly into an area-specific and time-specific warning. Furthermore, the warnings also need to be user-specific because the capacity of different users to withstand the impacts of a disaster are different. For example, the general warnings for the public would be different from those required specifically for the safety of a railway bridge during cyclone conditions because a strong structure such as a railway bridge is designed to withstand certain level of high winds and to permit a certain amount of river water flowing under it.
The warnings in this case have to be issued only if the anticipated winds and river-flow are expected to go beyond the specific safety thresholds. However; for the public, where houses of various types and strength have to face cyclone fury, the warnings will have to be in terms of the anticipated winds and rain in the hope that the individuals and communities will be prepared and take prompt action with the help of government and non-government organizations wherever the anticipated impacts are likely to prove dangerous. A warning has no value unless it reaches the users quickly and well in time. Therefore, quick communication is very important at the warning stage.
The inter-relationship between predictability, forecasting and warning is self-evident and should have been clear from the discussion in the preceding paragraphs. To repeat, a warning can-only be issued on the basis of a useful and reliable forecast and a disaster can be forecast only if it has an inherent predictability about it.
Even if an event is predictable, a useful forecast is available, the appropriate warning has been issued, and it has reached the users in time; the whole exercise will be fruitful only if the warning is believed and acted upon by the user. Therefore, credibility is very essential at every stage of the process of forecasting and warning. That is why the concerned agencies responsible for forecasting and warning of disasters strive hard to build credibility for their forecasts and warnings so that users develop confidence in these and take required action immediately and effectively.