Cape Verde systems timeframe

[Ladylight]

I see a lot of people saying the cape verde season will come to an end on X date, or after X date, the chance of a cape verde storm hitting the US is almost zero. Would someone be so gracious as to explain how the cape verde season can be predicted so precisely and what causes the risks to go down to almost zero after a certain point? I'd really appreciate any insight. Many thanks in a advance.

[meteorologist]

http://www.aoml.noaa.gov/hrd/tcfaq/A2.html

http://www.nasa.gov/mission_pages/hurri ... verde.html

http://www.hurricaneknowledge.com