You might be surprised but many fcst models don't get stratosphere-troposphere coupling at longer leadtimes. This is a figure from Riddle et al. (2013) showing correlations of 10 hPa Jan AO with AO at other months/levels. CFSv2 only sees correlation down to tropopause. pic.twitter.com/CdoHjAxjyT

— Dr. Amy H Butler (@DrAHButler) February 6, 2018