Cloud streets at Croome Court

We visited Croome Court in Worcestershire on a day where the cumulus clouds we forming into long lines parallel to the wind direction. These are called cloud streets. Cumulus is formed by convection. As the warm air rises, it cools and can hold less water vapour before becoming saturated. The process of condensation releases thermal energy by latent heat. This further drives the convection at the level of the clouds resulting in the fluffy tops of the clouds. I read a source that said that the neatly spaced rows of cumulus were caused by "longitudinal roll vortices". Hmm... In convection, when warm air rises, colder air sinks to form continuous loop. So the warm air rising at cloud level due to the latent heat must cause some colder air to sink somewhere. My guess is that colder air coming down is what separates the rows making circulation (vortices) that are stretched out longways (longitudinal).