Status:Ongoing analysis Material from: Linus


1. Impact

In the third week of July 2023, southern Europe and Northern Africa was hit by a heatwave. On 18 July Rome broke the temperature record reaching 41.8C (,C%20set%20in%20June%202022) with temperatures reaching above 47C on Sardinia. During a 2nd wave the week after even higher temperature was reached on the island.

During the heatwave, Greece was hit by severe wildfires, especially on the island Rhodes.

For a summary of about the temperature, see:

2. Description of the event

The plots below show analyses of z500 and T850 from 15 July to 27 July 00UTC, every 24 hour.

The plot below shows a time-series of daily 2-metre temperature (based on 00 and 12UTC ERA5 analyses) for central Italy (red) and southern Sweden (blue), starting from 1 May. Thin lines represent daily mean, thick lines 7-day running mean and dashed lines ERA5 daily climatology. One can see the strong heatwave over Italy during July with two peaks on 18-19 July and 2 July. The temperatures sharply dropped after 24 July peak. While southern Europe saw the heatwave, Northern Europe was dominated by milder conditions during July, after a heatwave in June.

3. Predictability


3.1 Data assimilation


3.2 HRES

3.3 ENS

The plots below show EFI and SOT for maximum 2-metre temperature on 18 July. Rome is marked with an hourglass.

The plot below shows the forecast evolution plot for maximum 2-metre temperature on 18 July for Rome. Mean of observations - green hourglass, concatenated 6-hour forecasts - green dot, HRES –red dot,  ENS blue box-and-whisker, ENS-EXT purple box-and whisker, ENS Model climate – cyan box-and-whisker and ENS-EXT Model climate – pink box-and-whisker. Ensemble mean as black diamonds. Triangle marks the maximum/minimum in the model climate based on 1200 forecasts.

3.4 Monthly forecasts

The plots below show 2-metre temperature anomalies for 17-24 July from different initial times with 7 days apart. While a warm western-central Mediterranean was captured at all lead times, the forecasts from 3 July and before missed the cold anomaly over northern Europe.

3.5 Comparison with other centres

4. Experience from general performance/other cases

5. Good and bad aspects of the forecasts for the event

6. Additional material