This case study will cover Xynthia, a storm that developed and evolved over the North Atlantic in late February 2010. Its progress was tracked by the ASCAT sensor onboard the EUMETSAT METOP-A satellite. First, a summary of Xynthia´s development and impact is presented in Chapter 1.1 and a short description of ASCAT winds is presented in Chapter 1.2. Chapter 2 focuses on various ASCAT observations of Xynthia, covering several phases of its life cycle. Throughout the whole case study you will be able to enlarge the images by clicking on them. If there are multiple images, hovering the cursor near the edge of the image will reveal a button that allows you to toggle between images. Chapter 3 includes a summary of the case study, and in Chapter 4 it is possible to overlay ASCAT winds with MSG observations and ECMWF model analysis and forecasts.