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The forecast vertical profiles show that the model was fairly good at representing temperature inversions.  However, the model locally missed clouds and fog by a small margins.  Such small errors had a large impact on surface temperatures.  The warm area in central northern Spain associated with high ground above the overnight inversion.

Settled anticyclonic weather is often dry but cold, with persisting low clouds and/or fog in some places and sunny and warmer conditions in others.  Vertical profiles often show IFS struggling to represent low level anticyclonic inversions.  The model tends to capture low level cloud cover reasonably well but vertical profiles suggest that cloud layer is shallower in the forecast than actually.  This can mean the model cloud breaks too easily allowing surface and 2m temperatures to rise too much.  In these conditions temperatures can be some 2°C to 5°C too warm under clearing skies, but can be as much as 10°C where low cloud or fog is particularly reluctant to break or lift.

Generally, the shorter the forecast period the better temperature forecasts are, but even at T+12h errors can remain widespread and still large in few places.

Fig9.2.1-2: Charts showing distribution of low cloud over Europe at 12UTC 26 Dec 2024.  Also shown are actual and forecast (T+12) vertical profiles for Essen and Muenchen and the errors between the forecast and observed 2m temperatures more generally.  The largest positive errors (reds and yellows, model T2m too high) are where the model has cleared the cloud too quickly and allowed incorrect insolation.   The negative  errors ((blues, model T2m too low) are where the model has maintained the cloud too and hindered insolation.  The cloud distribution is critical and users should anticipate likely deficiencies by monitoring available surface or satellite information. 

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