Strategic plan for HEPEX

Ensemble forecast techniques are beginning to be used for hydrological prediction by operational hydrological services throughout the world. These techniques are attractive because they allow effects of a wide range of sources of uncertainty on hydrological forecasts to be accounted for. Not only does ensemble prediction in hydrology offer a general approach to probabilistic prediction; it offers a significant new approach to improve hydrological forecast accuracy as well. But, there are many scientific challenges that must be overcome to provide users with high quality hydrologic ensemble forecasts.

A new international project the Hydrologic Ensemble Prediction Experiment (HEPEX) was begun last year to bring the international hydrological and meteorological communities together to demonstrate how to produce and utilize reliable hydrological ensemble forecasts to make decisions for the benefit of public health and safety, the economy and the environment. The second international HEPEX workshop at NCAR in July developed the framework for a strategic project plan. This includes some links between THORPEX and HEPEX as well as with GEWEX, IAHS and the WMO Hydrology Program. Funding for HEPEX activities depends on projects supported by HEPEX participants. Important sources of funding for U.S. participants include NOAA's Office of Global Programs, NASA's hydrology program and the NWS hydrology program.

Three main elements of the strategic plan are: test-bed activities, supporting data sets and development of a Community Hydrologic Prediction System (CHPS). Nine test bed activities have been proposed so far. These may have a geographical focus. They must include a science focus, user involvement, supporting infrastructure, plans for collaboration with other test-beds and share data with other HEPEX participants. A distributed data system will provide access to supporting data sets. The development of CHPS in the form of a system that can demonstrate capability, identify needed elements, and evaluate various components and techniques has tremendous potential and utility to all sectors interested in hydrologic ensemble prediction. The HEPEX web site is at http://hydis8.eng.uci.edu/hepex/.