while that may be in winter, its early fall, and as the Nina is expected (and likely starting to rot away already - al la enso disco), I'd be cautious at just using general Nina climo and say x causes y (even though its influence is larger right now...its sounds like its likely to start fading fast.
Enso is one in a myriad of factors to be considered when thinking longer term. If one loops back over the last several days of 500's on guidance, you'll note that its not really less defined, its just a different look to to the ridge/trough axis, which IMO is rather normal in seasons of transition as the fight of seasons is on, and that plays a large factor in forcing. Something for you to think about in the macro scale of things.