Could well be the SSTs. Pic is the current SST anomalies compared to our NAO sensitivity pattern (https://t.co/okxLhmkfqn, @HughScottBaker @ChrisEForest).

Warm subtropics in Pacific and Atlantic favour NAO+ (as does warm tropical Indian Ocean, though we don't get skill there) pic.twitter.com/kfslws4q3w

— Tim Woollings (@TimWoollings) November 29, 2019