Dr. Stensrud is well known for his studies on ensemble forecasting, mesoscale and convective-scale data assimilation, severe weather, convective-scale predictability, and the North American monsoon. He has authored more than 140 peer-reviewed publications and a textbook entitled Parameterization Schemes: Keys to Understanding Numerical Weather Models. Ensembles are groups of numerical weather prediction model forecasts valid over the same time period. Data assimilation is the process by which we integrate different types of observations together to form a three-dimensional description of the atmosphere at a given point in time. Severe weather in the United States typically refers to tornadoes, large hail and damaging winds, although tropical cyclones and flash floods also are considered severe in other countries. Predictability is the degree to which a correct forecast of future atmospheric state can be made. The North American monsoon is the seasonal wind shift that occurs over southwestern North America and is accompanied by a pronounced increase in rainfall.