It's the first time I see this kind of graphic, but that cone looks very suspiciously narrow and smooth, especially in the later days. Are they really properly

It's the first time I see this kind of graphic, but that cone looks very suspiciously narrow and smooth, especially in the later days. Are they really properly compounding the probabilities here? Like to create the boundary for the second day you have to sample a number of possible positions from the first day, recompute a possible path from these samples, and then expand the area out of these forwarded samples, based on uncertainty. The boundary at day 2 should be related to the samples that went the most off course. It looks like they just restart from the best-guess predicted position for day 2 which is already based on a prediction for day 1, and multiply it with the uncertainty, with a factor to account for one passing day. If that's the case this is really misleading. I imagine if they did it the way I'm thinking the cone could get very large very fast, but most importantly it wouldn't be smooth and symmetrical like this.