Status:Ongoing analysis Material from: Linus


1. Impact

In August south-western Europe had a strong heatwave, with many local records broken for both maximum and minimum temperature (see e.g During this heatwave e.g Lyon in France saw 17 days in a row with above 30°C (9-25 August), and culminated with 41.4°C on 24 August . In Spain, Bilbao on the north-coast set a new record of 44.0°C on 23 August.

2. Description of the event

The plots below show analyses of z500 and T850 from 19 August to 25 August 00UTC, every 24 hour.

The plot below shows time-series of 2-metre temperature over south-eastern France for 2023 (red) and 2003 (grey).

3. Predictability


3.1 Data assimilation


3.2 HRES

3.3 ENS

The plots below show EFI and SOT for 3-day 2-metre temperature on 22-24 August. Geneva is marked with an hourglass.

The plot below shows the forecast evolution for the 3-day (22-24 August) 2-metre temperature in the box over south-eastern France outlined in the map below, showing the analysis for the same period. The evolution plot includes daily extended-range forecasts (purple) and model climate based on 5-day (pink) and 30-day (brown) forecasts.


The plots below show EFI and SOT for maximum 2-metre temperature on 23 August. Bilbao is marked with an hourglass.

The plots below show forecast evolution plots for 2-metre temperature (left), T850 (middle) and 10-metre meridional wind (right) valid at 23 August 12UTC for Bilbao. The plots include ENS control (red), ENS distribution (blue) and analysis (green). The signal for extreme temperatures rapidly increased between 20 to 21 August, when the wind direction in the forecast shifted from northerly to southerly.

The plot below shows radiosonde profile from Santander on 23 August 12UTC and the forecast from 20 August 00UTC.

The plot below shows the error (shade) in the ensemble mean z850 from 20 August 00UTC valid 23 August 12UTC. The forecast is in black contour and analysis in red contour.

3.4 Monthly forecasts

The plots below show 2-metre temperature anomalies for 17-24 July from different initial times with 7 days apart.

3.5 Comparison with other centres

4. Experience from general performance/other cases

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

  • Early (2-3 weeks) signal for the heatwave
  • Problems to predicted the peak of the heatwave on 23 August along the Atlantic coast due to errors in the wind direction

6. Additional material