Looks like a sudden stratospheric warming could be underway, according to many meteorologists I've been following on Twitter. Michael Ventrice on twitter has some very good posts about it. Could mean a very cold month ahead for East U.S, and perhaps parts of Europe as well. Depends on whether or not the stratospheric anomalies couple with troposphere, but many are saying this will indeed occur. Last time we got something like this was 2018-19 winter, and it didn't couple to the troposphere so we didn't get major cold anomalies in the USA. But some of the coldest recent wintry periods for the Eastern USA, 2014-15, March 2018, 2009-10 and 2010-11, all had SSWs that coupled. Will be interesting to watch what happens. We may also see a rise in tropical convection from the ensuing tropical stratospheric cooling that usually occurs with SSWs at the poles.