Formation Mechanism for Non-Supercell Tornadoes
A: Some fronts are characterized by a very sharp change in wind speed and direction on either side of the front.
B: This strong horizontal wind shear can develop a series of small vortices along the front.
C: When the vortices develop under an updraft, the updraft stretches the vortex into a tighter and tighter circulation until a non-supercell tornado forms.
•Nearly
all tornadoes in California in wintertime develop along cold fronts by this process.