Shown here washing over the sky and rolling up to the Seattle shore, roll clouds are a rare treat usually awarded to those living in coastal areas. When a large pool of cooler, sinking air near the ground sweeps under moister, warmer air, the contrast can give the air a spin along a long horizontal axis, much like a rolling pin. The cool air may come from a sea breeze or a decaying thunderstorm. A roll cloud is often detached from all other nearby clouds, giving it extra prominence.
Click on the posters below to learn more about the conditions and to download free high-res print and postcard files!
For information on tornado strength and damage, checkout this tornado infographic by Weather Underground.
Get Away, Get Shelter, Get Low. How to stay safe in a tornado by Weather Underground.
See proof of how the Earth is changing with these interesting facts in this infographic by Weather Underground.
