Originally Posted by DJ77
See, for example, Tim Vasquez's analysis: no updraft higher than 40kt (about 4000 ft/mn), not "18000 ft/min, even higher" as mentioned, and no heat sink signature observed.
Some of you will be familiar with Ewa Wisnierska being sucked up into a thunderstorm on her paraglider in Australia a couple of years ago:
"Ms Wisnierska's top speed of ascent was clocked at 20 metres per second and her descent at 33 metres per second by an on-board tracking system"
Perhaps by chance she hit the upper limit quoted above. Perhaps it's not the upper limit.
8-10 m/s isn't unheard of even when simply thermalling in the core under a decent cu on a good day in the UK. Only twice that - 20m/s = roughly 4000ft/min - therefore seems pretty low for a supposed upper limit in the ITCZ.