We have posted on this research regarding polar vortex elongation at least three times this winter; please see our previous posts in January as well as this one. As we also state in the Footnotes of this post, we plan to discuss stratospheric wave reflection in a future post. In terms of this winter, it's not clear to us what metric is being used to state that the vortex has been stretched 10 times this winter.  As to whether or not the polar vortex caused the cold weather, as I responded to another commenter above, there is not disagreement that there could be a link between what is going on in the troposphere and the stratosphere, but rather what causes what in the case of stratospheric wave reflection. This is a subtle but maybe important distinction that we feel is not clearly resolved yet in research on the topic. For example, decades of research involving carefully designed model experiments has gone into showing how a weak or strong polar vortex influences weather patterns, and that this influence is real and causal (though perhaps small on average relative to internal tropospheric variability). While we know of a handful of these types of carefully designed experiments that have been done for this wave reflection type of coupling, there seems to be less consensus about whether it's the wave reflection off the polar vortex, and not corresponding and simultaneous tropospheric weather patterns, that is actually causing the cold weather. We do want to emphasize that we think research in this area is important and with continued studies, we can learn more about this linkage and its causality.