Book excerpt: Weather forecasting and climatology have traditionally been users of the world's fastest supercomputers. The recent emergence of massively parallel supercomputers as likely successors to current vector supercomputers has created an acute need to convert weather and climate models to suit parallel supercomputers with thousands of processors. Several major efforts are underway worldwide to accomplish this. ECMWF has established itself as the central venue for bringing together operational weather forecasters, climate researchers and parallel computer manufacturers to share their experience on these efforts every second year. The recent dramatic developments in supercomputer manufacturing have made the 1992 ECMWF Workshop timelier than before.