The Http JSON retriever would work well if you wanted to collect a specific offset, Like, if instead of having a point that meant 'Temperature Forecast' which is what I tried to provide, the Http JSON retriever would likely provide points that meant "The forecasted temperature two days from now" which could then gain history and you could chart the projected temperature two days out and compare it to the projected temperature one or three days out over time. I'm not sure why you would, but this does sound like a fine angle for data analysis. It could be interesting to time-shift those graphs over one another and see how the projections narrow to the reality, or something.
The tradeoff would by that the Http JSON retriever doesn't support getting multiple values for the same point from the same message, so you couldn't chart predicted temperature as you could with what I provided.