The warmest days (relative to average) of each December I plotted in R1 and ran them back 2 weeks at 500mb. There's a typical +NAM (+EPO/NAO) period in the week before the warmest December days. The loop ends with the highest departure days of each year. pic.twitter.com/KNLDtGgm9D

— Anthony Masiello (@antmasiello) October 30, 2019