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The typical predictability is currently approximately twice the timescale, but might ultimately be three times the timescale.  Small baroclinic systems or fronts are currently well forecast to around Day2, cyclonic systems to around Day4 and the long planetary waves defining weather regimes to around Day8.  As models improve over time these limits are expected to advance further ahead of the data time.  Features that are coupled to the orography (e.g. lee-troughs), or to the underlying surface (e.g. heat lows), are rather less consistently well forecast.  The predictable scales also show the largest consistency from one run to the next.  Fig4.1.3 shows 1000hPa forecasts from six sequential runs of HRES (identical to CONTROL-10CTRL) verifying at the same time. 

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It can be seen from the above that some of the HRES (identical to CONTROL-10CTRL) forecasts in Fig4.1.3 (T+96, T+108 and perhaps T+144) were quite good with respect to strong winds over Britain and Ireland but at the time the ensemble indicated that gale force winds were not certain. 

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