The new 35-day extended GEFSv12 forecast for the Arctic stratospheric #PolarVortex is now live at https://t.co/RZNZGS6oPT. It joins with the most recent ECMWF extended-range in predicting a weaker SPV during October (though model bias not accounted for here). pic.twitter.com/jKBmlrZk08

— Dr Simon Lee (@SimonLeeWx) September 25, 2020