the issue is statistical more than meteorological, in that they're using outdated averages that are getting overrun by global warming. that was the point of my sarcastic post a few weeks ago. a la nina is there, in relative terms, but not in absolute terms, so you go trying to apply the model and it breaks because it hasn't been adjusted for climate change effects. i'm reminded of a physicist with a broken classical model (this is a vague analogy, don't take it literally) that makes a newtonian prediction that is wrong because it wasn't adjusted for relativistic effects and can't figure it out, until somebody does the calculation and shows them; oh, i just needed to use the lorentz factor, and it's fine, silly me.
what does that mean?
it means you take the normal la nina model, as interpreted in a euclidean system (i want to avoid discussions of spherical geometry right now, although you should realize the earth is an ellipse and not fat) and translate it upwards in the y axis (that is north) by some amount.
i can't predict the amount. i don't have data.
but, the idea is as follows.
normally, la nina means it's warm and dry in florida and wet in california. this year, you should shift that northwards, so it's also dry and warm in georgia, at least, and maybe further north than that, and it's drier in california and wetter in oregon and washington and british columbia.
the shape of the jet stream should be the same, but it should be pushed northwards.
the models will continually get this wrong and you should expect a winter where the meteorologists are constantly incorrect, but you should be able to analyze it in terms of the translational effect noted.
where i am, in south detroit, the increased amount of warm energy in the atlantic ocean should keep the jet stream a little further north, and the precipitation systems should consequently end up more around hudson's bay than around the great lakes, or at least in the northern rather than southern great lakes region. that should largely result in a warmer, drier winter than average, overall, which is the opposite of a normal la nina. when we do get precipitation, it should fall mostly as rain rather than snow.