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• the standard deviation of the surface pressure pattern among the ensemble members is moderate (4hPa - 7hPa) but of less spacial extent than seen at T+120 (Fig8.1.2-6).  This implies less widespread variation (and hence uncertainty) among ensemble members in this area regarding MSLP values or location of any low pressure centres, although the detail of any low pressure centre or trough and/or its location is imprecise.
• the normalised standard deviation is much greater (2·5 - 5·0) than seen at T+120 (Fig8.1.2-6).  This implies variability among ensemble members is significantly higher in this area regarding MSLP compared to the variability expected at this forecast lead-time.  This is probably due to the depth and movement of possibly deeper low pressure centre(s) developed by ensemble members.
• the ensemble mean PMSL shows a sharp pressure trough (sharper than at T+120 (Fig8.1.2-6)) over northern Britain.  The large standard deviation suggests some ensemble members develop a low pressure centre or sharp pressure trough in the area.  However some ensemble members may not develop any low pressure at all.  This can be resolved by reference to the corresponding postage stamp charts.  The Ensemble Control Forecast shows development of a rather deeper and more vigorous depression (~983hPa) (deeper than at T+120 (Fig8.1.2-6)).  However, the Ensemble Control forecast should only be considered as one member of the ensemble. 

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