"Octants 8, 1 and 2 are the places where upward motion is strongest in the Atlantic Basin. The farther the MJO line is out away from the circle, the more development is likely. It is a product of the difference of land and water temps in the equatorial areas, and when the Atlantic is warm and the Pacific cool, it tends to focus on our area of the world. In the winter, the same type of situation is associated with troughs over the eastern and central U.S., and enhanced storminess.
The circular area and Octant 4 are neutral for tropical cyclones; the other octants are hostile for development."