Excerpt from my early November outlook....note that we also did indeed get an early reversal like 1981.
January 17, 1971: PV Split
December 4, 1981: PV Displacement
February 11, 2001: PV Split
January 2, 2002: PV Displacement
February 22, 2008: PV Displacement
January 7, 2013: PV Split
February 12, 2018: PV Split
March 20, 2025: PV Displacement
The majority of the SSW events are split between the mid winter months of January and February, with three events per month. There is also an outlier event in December,1981 and March 2025. The primary analog events of January 17, 1971 and February 11, 2001 were both accompanied by PV splits and are the only two members to appear in both of the QBO and solar analog composites. The primary analog event of February 12, 2018 also ultimately culminated in a split of the PV, and is a member of the QBO and ENSO composite. This lends more credence to the mid winter outlier scenario that contains 6/8 the analogs. Thus the favored timeframe for a SSW and subsequent split of the polar vortex is during the January 17 to February 17 timeframe, with an increased emphasis on the latter portion of this window, which favors late season NAO blocking to commence roughly in early March.