I am sure Glenn will confirm but the N swell is generated off the Eastern US coast. That is why it is so well forecast. The various wx buoys pick it up as it moves south toward the Carribean. Wind generated chop is small but with a shorter interval and steeper face. The interesting thing is even a large N swell is very comfortable to sail in. It's a nice smooth motion unlike the pounding wind chop gives. The N swell becomes nasty when it reaches shallow water unless you are a surfer then it's fantastic!