A front forms when two or more air masses come in contact with each other. The front is usually a line where they meet.
Sunlight warms the equatorial waters more than polar waters. The tropics receive the most sun because of the tilt of the earth's axis. The uneven heating leads to convection.
Wind shear can result in the formation of a tornado.
a front
What does this symbol indicate on a weather map?
low pressure
The Gulf Stream.
Persistence
When a cold FRONT catches up to a warm FRONT it is called an occluded front.
When a cold AIR MASS displaces a warmer AIR MASS it is a cold front.
Occluded front
The polar jet stream lies between the polar easterlies and trade winds