The last time a -4-5 sigma AAO event occurred in JJA was late July-Aug 2011. Ironically, it was also preceded by & coincided w/ strong CC Kelvin Wave (CCKW) activity in the Pacific & Western Hemisphere. Don't even need filtering to see CCKWs propagating thru the raw VPa field pic.twitter.com/VeFR1otp7S

— Eric Webb (@webberweather) July 29, 2019