The November update of the ECM is now suggesting a weaker than average stratospheric polar vortex at 10hPa during December 2019 contrast to last month's update. However, the Glosea5 is less confident on this with quite a high spread especially in January. It's important to note that the Glosea5 has a better verification record than the seasonal ECM but at the end of the day, they're long range models so prone to huge changes.
https://twitter.com/SimonLeeWx/statu...62609595768833
Yesterday's GFS backed away significantly from the SPV getting disturbed with +AO filtering down through the atmosphere in FI whilst still forecasting quite a weakening in the zonal mean zonal winds at 60N 10hPa. The ECM showed similar but actually also showed a strengthening again at the end of FI.
Very confusing picture.