Confidence levels of flood and drought forecasts from El Nino/Southern oscillation indexes

Ropelewski and Halpert (1996) have identified 19 regions of the world whose precipitation characteristics are related to El Nino/Southern Oscillation phenomena. Although the teleconnections are now extensively described in literature, scientists are still groping to model the nature and strength of the teleconnections. To provide a lumped picture Eltahir (1996) have used the discriminant analysis approach to predict flood and drought conditions in the Nile river. To average out temporal variability Chiew et al. (1998) have proposed contemporaneous averaging of data for a period of up to 36 months. These are useful approaches to provide a broader picture, but a more efficient tool for decision making purposes would be if each forecast is associated with a confidence level. Construction of confidence level has to start from the variability of the input data. As models are developed to process the input data, statistical equations can also be developed which can capture the propagation of the variability of the input data through the models. Wasimi (1994) describes how statistical equations can be applied to capture the propagation of variability in numerical analysis. In this paper methods are developed which can associate confidence levels with climatic forecasts made through remote controls such as Fl Nino/Southern Oscillation indices.