GRAND RAPIDS, Mich. (WOOD) — A cold front Wednesday produced the perfect conditions over West Michigan Wednesday for “cloud streets” to form.
Cloud streets are also known as horizontal convective rolls. The phenomenon is not necessarily rare but often stunning, with rows of similarly looking clouds stretching across the sky.
Cloud streets form when cold, stable air air spills into an environment with just enough moisture at cloud level. The stable environment keeps the clouds from becoming too tall, and also allows for the clear spaces between lines of convective clouds to form. The cumulus clouds that form orient themselves with the mean wind. Beneath each row of clouds are little convective vortices. The clouds form where the air is ascending within the vortices. The clear spaces form where the air is descending.
Cloud streets are especially common when cold air rushes over bodies of water. It is also quite common during lake-effect! Often in West Michigan when the winds are right, bands of clouds and snow organize into lines, or streets, similar to what was spotted over West Michigan on Wednesday.
