Setting aside the unpredictable variable of the weather, it would still appear that unanticipated events may well occur in 2019 as a result of fundamental changes in the system that have not yet been appropriately understood or articulated.
As Rod implied, that's presumably a big part of why many of us are here. It's fascinating to watch. As for detailed hypotheses based in a best-as-possible understanding of current evidence, I'm not sure such experts are here. (It would be better to read the scientific literature.) But I'd venture that
no one, top experts in the field included, has a very good idea about what is going to happen.
P.S. I've already stated my best guess, which is, at some point a combination of:
+ Peripheral heat, which melts ice and snow, raises SSTs, and feeds storms -- note that this is not random but a systemic effect;
+ Export of ice into the Atlantic, which we've seen in an unprecedented amount this year (although I'm not sure how many have taken notice; nor whether it's a systemic change that will persist);
+ Halocline weakening, which if I understand it correctly is dependent on the volume of melting ice and accumulates over years and decades;
+ Related changes to atmospheric circulation that I don't understand well, but which at least include a weakening jet, due to reduced temperature differences between the north pole and the continents, and which seems like it may result in less protection of the arctic from injections of warm, humid air masses (and which we've already seen in real time this year and may see more of);
+ And probably additional and more important factors that I don't know about.
All of this is accumulating and will at some point add up to disaster.