The ECMWF offers additional information on their ensemble forecasts describing the behaviour of the individual ensemble forecast members with respect to each other. This comparison happens by grouping similar members into clusters.
The information offered can be grouped into two categories:
Climatological weather regimes are computed for cold (October to April) and warm (May to September) seasons. Four patterns, consistent with those documented in the literature (see for example Michelangeli et al. 1995) are considered:
a strong positive anomaly over the Greenland area, together with a trough elongating from the southwest to the northeast Atlantic Ocean
an east-west dipole, [...] associated with a pronounced wave structure
a trough centered over Iceland together with a small-amplitude positive anomaly in southern part of the domain
a ridge in mid-Atlantic
First time step of the clusters existence (in hours since model start)
Last time step of the clusters existence (in hours since model start)
Geopotential Height Cluster
Since the grouping of the ensemble members into clusters is based on the geopotential height at 500hPa, that parameter can also be queried for each cluster
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