Arcus clouds


In this section you will learn how and why arcus clouds form, why some storms produce a shelf cloud, while others produce a roll cloud. You will learn to visually identify a shelf cloud and a roll cloud.

On the following pages you will find:

  • Interactions between the storm’s inflow and outflow that form arcus clouds.
  • What is a shelf cloud and how it forms.
  • What is a roll cloud and how it forms.
  • 15 examples of shelf and roll clouds: from weakly developed to exceptional cases, in different seasons.

Examples include variations of shelf and roll clouds: weakly defined, strongly defined, shallow, deep shelf clouds, multi-level, …