HBB, no problems. As you note, sometimes there is a very smooth gradient and the coffee remains where intended! Other times ….!!!! Often, there is no logic behind the outcome. I have always adopted the approach where I expect the worst. After all, one can only be pleasantly surprised by a potential bad event not taking place! Far better than being caught unawares. With Jetstreams in particular, there is no reason to assume a constant change in velocity as you approach the core. Why? If you ever find out, please do let me know!!!! LOL!
Cheers, H ‘n’ H