Flapping, debouncing, jitter, sensor noise, etc.: I think a few people are trying to say the same thing, so I’ll try to answer this collectively: The data you posted seem fairly smooth in the highlighted part, but this may not always be the case. You probably don’t want to trigger immediately, because the larger trend might be going one way, but for a moment it could go in the other direction, so you’ll get a false positive (look at your initial post in the period between 15h00 and 19h00).
Before I learnt about the trend sensor Tinkerer posted, my suggestion was to smooth the data more before taking the derivative. With the trend sensor, you don’t need that part though (if I read the docs correctly):
min_gradient will probably do the job. It does seem you’d need to set up 2 of these if you want to track both an upward and downward trend (from your initial post it seems you only need the former).