Equatorial Trough
The quasi-continuous area of low pressure between the subtropical high pressure areas in both the Northern and Southern Hemisphere.
Low Pressure System
An area of a relative pressure minimum that has converging winds and rotates in the same direction as the earth. This is counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. Also known as an cyclone, it is the opposite of an area of high pressure, or a anticyclone.
Subtropical
The region between the tropical and temperate regions, an area between 35° and 40° North and South latitude. This is generally an area of semi-permanent high pressure that exists and is where the Azores and North Pacific Highs may be found.