Material from: Linus

1. Overview

The first week of August was extremely hot in central Europe, and both Austria (41.2 °C) and Slovakia (41.4 °C) broke their national temperature records on 5 August.

2. Analyses and Observations

2.1 Event Definition

In this evaluation we will focus on the 2-metre temperature as a 3-day mean between 3-5 August and the instantaneous temperature at 12UTC on 5 August both for a 0.5x0.5 degree box centred on Vienna (48.2N, 16.4E).

2.2 Analyses

The plots below show analyses of T850 and z500 from 28 July to 9 August, every 24 hour.

2.3 Observations

The plot below shows observations around Vienna (black) and IFS-ENS from 3 August 12UTC.

2.4 Climatological perspective

3. Forecasts

3.1 Data assimilation and observation usage

3.2 Single Forecasts for the event based on 00UTC forecasts (defined in Section 2.1)

The plots in this section shows the 2-metre temperature at 12UTC on 5 August.

Observations and analysis for the event

Control forecast (IFS 9-km resolution)

DestinE (IFS 4.4km resolution)

AIFS-single (AIFSv1.0 ~0.25 resolution)

AIFS-ENS control (~0.25 degree resolution)

3.3 Ensemble distribution

EFI (based on IFS 9-km ensemble)

The plots below show the EFI for 3-day 2-metre temperature on 3-5 August.

Forecast Evolution plot

The plot below shows the forecast evolution for 2-metre temperature at 12UTC on 5 August around Vienna.

The plot below shows the forecast evolution for 2-metre temperature for 3-5 August for Vienna from the sub-seasonal forecast, doing back 45 days.

3.4 Sub-seasonal forecasts

The plots below show ensemble mean of the weekly average temperature 3 -9 August from different initial dates of the sub-seasonal forecasts.

3.5 Comparison with other centres

4. Hazard Forecasts

5. Dedicated Experiments

6. Event Summary

6.1 Good and bad aspects of the forecasts for the event

• 3-day event over Vienna around 3 standard deviations (99.865 percentile)
  June, July and August monthly records for Austria has been broken this year
• Warm signal present in the sub-seasonal range
• Signal very strong ~12 days before the event

• Signal in IFS ensemble stronger than AIFS 8-12 days before the event
• 12UTC temperatures similar in IFS and AIFS in the short-range (not shown here)
• Large local variability in daily minimum temperature in observations – not captured by the ensemble

6.2 Experience from general performance/other cases

7. Additional material