We are currently in a descending westerly phase of the QBO, with easterlies below 20 mb. If easterlies persist at 50 hPa by late October, that could be one factor pushing the #polarvortex to be weaker in early winter. https://t.co/gg1OaDoDSK pic.twitter.com/QPHGfAuVh0

— Dr. Amy H Butler (@DrAHButler) August 22, 2018