What is "AST"? As I track Tropical Storm Chris and read the National Hurricane Center advisories, I note that the time that a given advisory is issued is "AST", and not "EST". AST means "Atlantic Standard Time", and it is an hour earlier than Eastern Standard Time.
But to make things more confusing, those of us who live in Florida are, during the summer months, that is during the hurricane months, on EDT. EDT is Eastern Daylight Time. (I thought we were on "Daylight Savings Time", but they eliminated the "Savings" from the appellation. This would be appropriate, because the time change in the summer, in my humble opinion, saves nothing. I could be wrong about this, however.) EDT is an hour earlier than EST and, therefore, it is the same time as AST.
There is Atlantic Daylight Time or ADT. But the website to which I linked advises that ADT is only used in some parts of Canada, not down where hurricanes roam.
So, when the National Hurricane Center posts an advisory during the summer months at a given "AST" time, its the same as "EDT" time here in Florida. I think it would be fine for the National Hurricane Center to post its advisories with the note that the given time is "AST and EDT".