...
You will find two CDS catalogue entries for real-time forecast monthly anomalies; each contains the anomalies for the ensemble mean for each system and the individual ensemble members.
Anomalies are just available for real-time forecasts start dates (from 2017 onwards).
One dataset contains surface (or single level) parameters, the other contains variables on 11 pressure levels spanning 925 hPa to 10 hPa.
...