Blocking high

blocking high

(Or blocking anticyclone.) Any high (or anticyclone) that remains nearly stationary or moves slowly compared to the west-to-east motion "upstream" from its location, so that it effectively "blocks" the movement of migratory cyclones across its latitudes.
A blocking high may comprise a smaller-scale effect than that associated with large-scale blocking.

1. The obstructing, on a large scale, of the normal west-to-east progress of migratory cyclones and anticyclones.

An atmospheric anticyclonic circulation, a closed circulation. The wind in an anticyclone is in the clockwise direction in the Northern Hemisphere and counterclockwise in the Southern Hemisphere.