
Post by
zezo | 2019-01-15 | 10:54:18
If you ask about the predicted tracks for the Jules Verne - they should not really change between updates (unless you are at "Start now")
The 16-day forecast is finished downloading at 5:00/11:00/17:00/23:00 UTC, and the predictions table is generated about 5 minutes later, so there should not be a any between e.g. 11:00 and 15:35, then between 15:35 and 17:00 new data is fed into the router incrementally.
While underway small changes are inevitable at every step. Like exact tack/gybe times, exact directions and so on. There exists a huge amount of routes with very little difference in the outcome, and the router picks one at random. It has no memory of the routing it did for you 5 minutes ago. Also, exact following of the optimum angles is not guaranteed (and sometimes there is a optimum range like TWA 141-143 with same VMG), so you can do a bit better by checking the polars for the exact current wind speed.