Given the warm SST's, the MJO cycle duration is at it's shortest, around 30-40 days. Lack of convective budget with a weak walker cell increases the propagation speed.
Love your posts..you're really tearing it up. Agreed that mean period frequency has been elevated over the last 3-4 months due to ENSO/QBO forcing on eddy transport.
What are you referring to when you mention the lack of a convective budget? I get that SST anomalies are somewhat uniform longitudinally for a Niño (destabilizes Walker-Hadley intensity ratio), but the tropical tropopause is higher than normal, and macroscale mixing is quite deep.
At this point, I say our window of opportunity is ~Dec 1-10 while the MJO is centered around the Maritime Continent. After that, convection moves into the Pacific, with cold favoring the Central US at first, then shifting into the East. What happens from there is up in the air. Not saying we can't see any cold, just that tropical forcing favors warmth in the west for 2/3 of December. If a new MJO wave initiates over the IO, given the current MJO duration, early-mid January could be our next major window of opportunity, which lines up with the LRC so far this season. I was linked a great article by @webberweather, which illustrates the MJO cycle duration by month. Keep in mind, as mentioned above, cycle duration is on the low end this season.
Great analysis! Best of luck to you here. Personally I favor January over December. I agree with your thoughts on the longwave progression, but I suspect most of December will be highly zonal due to the observed poleward AAM transport since September and the near record low in the Walker-Hadley intensity ratio. Biggest question for me is in the timing of the SSW/PVA implosion..whenever it occurs, it'll lead to extreme cold for at least 3-5 weeks, I suspect..