Weather forecasting and climatology have traditionally been users of the world's fastest supercomputers. The emergence of massively parallel supercomputers as likely successors to current vector supercomputers has resulted in the conversion of weather and climate models to suit parallel supercomputers with thousands of processors. The European Centre for Medium-Range Weather Forecasts has established itself as the central venue for bringing together operational weather forecasters, climate researchers and parallel computer manufacturers to share their experiences about these efforts every other year. This book presents an excellent cross-section of the results achieved so far in this demanding area of high-performance computing.