This book collects together White Papers that have been written to describe the state of the science and to discuss the major challenges for making further advances. The authors of each chapter have attempted to draw together key aspects of the science that was presented at WWOSC-2014. The overarching theme of this book and of WWOSC-2014 is “Seamless Prediction of the Earth System: from minutes to months”. The book is structured with chapters that address topics regarding: Observations and Data Assimilation; Predictability and Processes; Numerical Prediction of the Earth System; Weather-related Hazards and Impacts. This book marks a point in time and the knowledge that has been accumulating on weather science. It aims to point the way to future developments. We hope it will be of great interest to researchers and practitioners alike. We also hope that it stimulates and excites the next generation of weather scientists. Finally, we would like to thank the authors who have contributed so much in creating this volume.