For the past few months, a lot of the keywords that my blog posts appear for keep on dissapearing and reapparing at random dates on Google. Can someone explain why that is?

Example:

Keyword = "San Diego Conquistadors"

October 10-13th: Listed in Search

October 14th: Gone

October 15th-20th: Listed in Search

October 21st-25th: Gone

October 26th-Present: Listen in Search

I'm using UberSuggest to track rankings.