CocoaBill wrote:If that blob maintained those red topped heights for 48 hours.........

- we have a little TC to contend with......
Where on earth do you get that idea?
The whole "persistence" idea is both mis-used and overrated.
Yes, all things which DO form into TCs had persistent convection, however, plenty of features over water with persistent convection don't form TCs and never really had the chance to.
There are plenty of upper-level generated features that can persist for quite some time (3+ days) over tropical waters that never really have any particular chance to be a TC. And there's no magical time of persistence of these features where they suddenly become something that needs to be watched for TC development.