l'altra cosa che lo rende evento molto raro è la precocità dell'evento in rapporto alla sua portata
del resto

The strat. vortex is currently weaker than ERA interim average
and is forecasted to remain weaker than average (according to EPS-mean)
0 of 21 members have stronger vortex than average at the
last forecast step (2019-01-10 00:00:00)

The zonal mean zonal wind at 10 hPa 60N is today (GFS analysis): 11.6 m/s
Weakest zonal wind at 10 hPa 60N in ERA interim record for todays date is: 6.3 m/s 2001
Strongest zonal wind at 10 hPa 60N in ERA interim record for todays date is: 61.8 m/s 1990


quanto siamo vicini al valore minimo record e distanti dal massimo la dice lunga in proposito già oggi