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The Regime Frequency Histograms are derived using 4-regime scheme.

Real time example of Extended Range Weather Regime Frequency histogram.

Fig8.2.7.1: The plot shows the cumulative weather regime frequency from the extended range ensembles (DT 14 March 2019).  The coloured bars indicate the number of members forecasting a specific regime for each day of the forecast (Blue:NAO+, Red:Blocking, Green:NAO-, Purple:ATR).  Inclusion of an ensemble member within a regime type gives no indication of the strength of the solution within that type (e.g. a strong or weak Blocking regime).  Members that are not close enough to any of the four weather regimes are represented by the grey bars (members with no regime attribution).  Bars with diagonal lines represent the regime attribution of ensemble mean fields.

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The regime Projection Diagrams are derived using Mirror 2-regime scheme.

Real time example of Extended Range Two-dimensional Regime diagram.  

Fig8.2.7.3: NAO/BL phase space diagrams for the periods: Days5-11, Days12-18 and Days19-25, from extended range ensembles with DT 14 March 2019 (same as in Fig8.2.7.1).  Colours represent the proportion of members that have a similar mean solution during each seven day period.  The shaded area gives an indication of the spread of regime types.  Colours represent different proportions (taken as probabilities) of a combination of regime types (Note the colours represent different probabilities on each diagram).  Within the central circle there is only a weak indication of regime type.

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Read more about the use of "Weather regimes" at ECMWF (2020 article)

_{Updated/Amended 27/01/21 - Clarifications regarding the two methods of regime subsetting.}