IMHO, it's a little odd to change your log file by SIZE rather than by date. Most system logs (in unix or linux) rotate on a weekly or monthly basis, and not based on size...This is something I like for various reasons, and also something which, if implemented, would solve your problem.
Eight years later, I don't know what the hell I was talking about here: there are tons of places where you want to rotate by size, because daily/weekly/monthly rotations can yield MASSIVE files which can cause serious issues.
From a more experienced perspective, the real question is why you'd want to sit and continuously tail a file that's growing so fast that you're rotating it more than daily...It'd be like watching the Matrix stream by.
These days you'd be better looking into some big data log aggregation like Splunk or Sumologic, where it can filter log events into classes and trigger based on specific log values...No need for watching live logs at all.