Temperatures in the summer of 2017 in the UK crashed on the 20th of July and have never recovered in the almost three weeks since it’s been since then. You can see clearly how the temperature has almost flat lined in the NCEP reanalysis data for the grid point 52.5° north and 2.5° west (just to the west of Birmingham), with almost all the 6 hour anomalies negative since then, negative (fig 1). I remarked in a blog only yesterday about how unusually flat the daily CET values had been since the 20th of July. Its probably all tied up with that ‘ribbon of high wind speed high in the atmosphere‘ that we like to call the jet stream.
Meanwhile in stark contrast to the UK, just to the northeast of Rome in Italy, at the 42.5° north 12.5° east grid point, things have been slightly different. A part from three short cold spells, the temperature anomalies there have all been well above average since early June (and before), with the recent heatwave this month clearly evident.