Early-season weak vortex event incoming? Yesterday's ECMWF extended-range takes ensemble-mean U10-60 down to 10th percentile of model climate by second half of Oct. Z500 anomalies at the onset suggest amplification of planetary wavenumber-1, with Scand/Ural block + Aleutian low. pic.twitter.com/8mvOhVflkf

— Dr Simon Lee (@SimonLeeWx) September 24, 2021