Material from: Linus

1. Overview

In the end of April 2025 Western Europe experienced unseasonally high temperatures.

2. Analyses and Observations

2.1 Event Definition

Currently based on the 2-metre temperature for Reading (51.5, 1W) on 30 April 12UTC. An evolution plot is also available for the 3-day mean temperature (29 April -1 May) for a 0.25x0.25 degree box centred on London-Heathrow (51.5N, 0.5W).

2.2 Analyses

The plots below show analyses of T850 and z500 from 26 April to 2 May.

2.3 Observations

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)

Observations for the event

ECMWF analysis

Control forecast (IFS 9-km resolution)

DestinE (IFS 4.4km resolution)

AIFS -single (AIFSv1.0 ~0.25 resolution)

AIFS ensemble (AIFS diffusion ensemble ~1 degree resolution)

3.3 Ensemble distribution

EFI (based on IFS 9-km ensemble)

The plots below shows the EFI for 3-day mean temperature 29 April 1 May.

Forecast Evolution plot

The plot below shows the evolution plot for the 2-metre temperature on 30 April 12UTC for Reading.

Legend:

Observation - green hourglass
Analysis - green dot
ENS CF - red dot
DestinE - dark-green dot
AIFS-single - cyan dot

ENS distribution - blue
AIFS-ENS-CRPS distribution - pink
ENS m-climate - cyan
ENS m-climate maximum - black triangle

The plot below shows the evolution plot for 3-day mean temperature for London-Heathrow (see event definition). Same legend as above.

3.4 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

6.2 Experience from general performance/other cases

7. Additional material