Why is there a difference in persistence?

I watched six hours of this over my house today. Whether intentional or unintentional it's there.

Check out Weather as a Force Multiplier :Owning the Weather in 2025 PDF

The footnote about Operation Popeye is fascinating - where cloud seeding was used in an attempt to cause extended rain on the Ho Chi Min trail - supply route.

The 8:27 mark on this video - I wonder what can explain the difference in the persistence?


This video from same series is entertaining - includes Operation Popeye and other fun stuff: