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Created by
Linus Magnusson, last updated on Oct 28, 2026
7 minute read
Material from: Linus, Fernando
1. Overview
Storm Adam was a high-impact DANA (cut-off upper-level low) that affected large parts of the western Mediterranean in mid-October 2026. Eastern Spain was initially hardest hit during 17–19 October, particularly Valencia and Alicante, where exceptional rainfall caused severe flash and river flooding. Pego recorded 632 mm in 36 hours, and more than 2,000 people were evacuated. Four deaths were reported during the Spanish storm episode.
The system subsequently generated major rainfall over southern France, affecting Languedoc, Provence and the Cévennes. For example Météo-France recorded 187 mm at Aigues-Mortes in the Gard and 279 mm at Salon-de-Provence. The most extreme French rainfall occurred in Corsica. Météo-France reported more than 600 mm in 24 hours at Solenzara.
Meteorologically, Adam combined cold air aloft with very warm, moisture-rich Mediterranean air. Persistent low-level moisture convergence and repeated convection produced exceptional rainfall from eastern Spain through southern France and Corsica.
In this report we focus on the forecasts for southern mainland France, while Daily reports covered the Spain and Corsica parts.
2. Analyses and Observations
2.1 Event Definition
The evaluation will focus on the 2-day precipitation between 19 October 06UTC and 21 October 06UTC for a 0.5x0.5 degree box centred on 43.6N, 5.1E near Salon-de-Provence in southern France.
2.2 Analyses
The plots below show analyses of MSLP and 6 hour rainfall from 17 October 00UTC to 21 October 00UTC, every 12th hour.
The plots below show z500 and T850 from 13 October to 21 October 00UTC, every 24 hour. On 18 October a trough formed over Spain and slowly moved to the east.
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 and analysis for the event
While the box focus on Salon, you can also note the black dot over Corsica, which is the +600 mm observations in Solenzara. This was not captured by the ECMWF analysis.
Control forecast (IFS 9-km resolution)
While the IFS control forecast indicated heavy rainfall in Southern France, it had problems to capture the part around Salon where the most intense rainfall fell.
DestinE (IFS 4.4km resolution)
AIFS-single (AIFSv1.0 ~0.25 resolution)
The AIFS-single had a consistent prediction of the rainfall pattern up to 3 days before the event, but with a focus north-east of Salon, probably connected to orography.
AIFS-ENS control (~0.25 degree resolution)
In the AIFS-ENS control the rainfall is more fragmented and probably on average a bit less than in AIFS-single.
Hybrid Deterministic
Hybrid ENS perturbed member 1
3.3 Ensemble distribution
EFI (based on IFS 9-km ensemble)
The plots below show the EFI for 3-day precipitation for 19 October 00UTC to 22 October 00UTC, from different initial dates (19 October back to 13 October). A reasonable signal for the event hitting southern France appeared in the forecast from 16 October. Earlier forecasts had the event further to the west.
Forecast Evolution plot
The plot below shows the evolution of the forecasts for 2-day precipitation (19 October 06UTC - 21 October 06UTC) for the box near Salon-de-Provence defined in Section 2.1.
Below is the same as above but without the Hybrid model.
In the evolution plot for the precipitation over Salon we see the signal got stronger between 15 to 16 October, in a similar way in IFS and AIFS ensembles. AIFS-single, seems to be ahead of the other deterministic forecasts but IFS control had one very extreme forecast around 14 October.
3.4 Sub-seasonal forecasts
The figures below shows verification plots for weekly precipitation anomaly for 19-25 October. Most of the signal for southern France is lost in forecasts before 14 October. For western Mediterranean the signal appeared earlier around 10 October.
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
- All forecasts missed the local extreme over the French South-coast (Salon), while had a stronger signal in the mountains to the north-west.