Horizontal convective rolls
From AMS Glossary
horizontal convective rolls
(Also known as horizontal roll vortices, boundary layer rolls.) Counter- rotating horizontal vortices that commonly occur within the convective boundary layer; their major axes are aligned with the mean boundary layer wind-shear vector.
The depth of the roll circulations is consistent with the depth of the boundary layer; the wavelength, measured from updraft to updraft in the cross-roll direction, is about three times the boundary layer depth.