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The cold front was associated with very thick cloud cover and patchy rain.  2m temperatures were low for this time of year under the frontal cloud, and in the post-frontal cold air temperatures were only between 13°C and 20°C.  The T+72 forecast for Bucaresti showed no cloud, temperature 29°C, and SW'ly low-level winds.  But observations showed thick cloud layers, temperature 19°C, and NE'ly low-level winds.  However, the ensemble members showed uncertainty in the position of the cold front and the spread in temperature was very large in the whole boundary layer.

FigXXXFig9.1-3: Errors in 2m temperature over the Balkans T+72 DT12UTC 25 June, VT 12UTC 28 June 2023.  The cold front advanced further than predicted with extensive cloud depressing temperatures ahead of the front and allowing an inflow of colder air to the rear.  Colours show where forecast temperatures are too warm (red and purple), too cold (blue).

FigXXXFig9.1-4: Vertical profile showing differences structure of the airmass at Bucaresti.  The T+72 forecast for Bucaresti (red) showed no cloud, temperature 29°C, and Sw'ly low-level winds.  The radio sonde data showed thick cloud layers, temperature 19°C, and NE'ly low level winds.

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