Positive AAM is better for higher latitude blocking. Blocking is more prevelant during El Ninos (+AAM) rather than La Ninas (-AAM) during the winter time and this is related to the location of tropical forcing.
Key word here is location of the tropical forcing (MJO)If this is good blocking can still be achieved meaning you want p8,p1.p2,sometimes p7 if in January.Plus the SOI is hinting more El Ninoish lately (-7.63 today)
The AAM weakened but has leveled off and is ticking back upwards and is still plenty positive.I have my own opinion what drives this but I think it can stay positive most of the month.It may dip again after Jan 16-18th but not drop to negative,patterns often get stuck in low solar as well.
Just my opinion.