The equatorial air is simply slamming up against the Arctic vortex. The occurrence sorta looks like the head of a hammer when it manifests. It is noted over the center of the North American continent at hours 1430z to 2130z.
It's most noted and more easily noted over the Atlantic at 1530z. The air mass starts to 'pile up' and the velocity stalls causing an internal rotation of the air mass leading to vortexes. The formation is poorly described as a hammer but it gives those interested something to focus on while sorting out the dynamics.
