The forecaster sees that the western mountainous region of Panama is forecast to have significant rainfall in the next 6 hours, exceeding 100 mm/6 hours in some areas. The first question the forecaster is likely to ask is: “what is the rainfall forecast for the next 6 hours?” At that time, FFGS, based on the Weather Research and Forecast mesoscale numerical weather prediction model, indicates the precipitation forecast (Figure 1a) for the region. The forecaster is told that it has been raining in western Panama. To demonstrate use of products of the GFFG system, imagine a hypothetical situation in which an operational forecaster in Panama begins a shift at 1 p.m. The design aims to reduce loss of life and human suffering from the devastation caused by flash floods, and is consistent with an end-to-end forecast response process.

An extensive training programme – designed to allow forecaster to adjust system products in real time based on local experience and local up-to-the-minute information – complements the system. Real-time information on precipitation is provided by gauge-adjusted, satellite-based rainfall estimates and, when available, radar-rainfall estimates. The system has also been successfully implemented at a subnational scale. One is a stand-alone system for an individual country, while another is for Northwest South America (emanating from the Zarumilla River Basin pilot application), which will likely include three countries. Four – Haiti and Dominican Republic, South Asia, Chiapas and Southeastern Asia-Oceania – are under implementation, covering an additional 17 countries. Six regional FFGSs – Black Sea and Middle East, Central America, Central Asia Region, Mekong River Commission, South Africa Region and South East Europe – have been completed and have become fully operational, covering 41 countries. The GFFG system consists of regional systems (referred to as Flash Flood Guidance Systems (FFGSs)) that allow incorporation of local information into system products and development of regional cooperation in hydrometeorological forecasting.

It uses real-time in situ and remotely-sensed data, numerical spatially distributed land-surface hydrological models and mesoscale numerical weather prediction models. The system provides the necessary products to support development of warnings for precipitation-induced flash floods. These products pertain to the threat of potential small-scale flash flooding over large regions with high resolution. The primary purpose of the Global Flash Flood Guidance (GFFG) system is to provide real-time guidance products to forecasters worldwide.

Areal flood definition