Status: Ongoing analysis Material from: Linus
1. Impact
In the first days of October, storm Alex impacted large parts of western Europe. On the end of 1 October the cyclone rapidly developed and a sting jet feature formed and hit the coast of Brittany in France. The next day parts of south-eastern France and north-western Italy saw record rainfall and left at least 3 people dead.
http://floodlist.com/europe/france-italy-floods-storm-alex-october-2020
https://www.bbc.co.uk/news/world-europe-54402096
2. Description of the event
The plots below show analyses of t850 and z500 from 30 September to 4 October, every 24h.
The plots below show analyses of MSLP and 6-hour forecasts of precipitation from 1 October 00UTC to 4 October 00UTC, every 12th hour.
Warnings on Meteoalarm for 2 October from the morning of 1 October.
The images below show satellite images from 1 October 12UTC to 2 October 00UTC, every 3rd hour to illustrate the development of the sting jet over Brittany.
3. Predictability
3.1 Data assimilation
3.2 HRES
The plots below show 24-hour maximum winds gusts (1 Oct 12UTC to 2 Oct 12UTC) from observations and HRES forecasts with 1 day apart (all 00UTC).
The plots below show 24-hour precipitation (2 Oct 06UTC to 3 Oct 06UTC) from observations and HRES forecasts with 1 day apart (all 00UTC).
3.3 ENS
The plots below show EFI for 24-hour maximum wind gusts on 1 October.
The plot below shows the forecast evolution for 24-hour maximum (1 Oct 12UTC - 2 Oct 12UTC) wind gusts in the box over Bretagne outlined in the EFI plots above. The plot includes ENS (blue), HRES (red dot), ENS control (purple dot), observation (green) and model climate (red).
------
The plots below show EFI for 24-hour precipitation on 2 October.
The plot below shows the forecast evolution for 24-hour accumulated precipitation (2 Oct 06UTC - 3 Oct 06UTC) in the box over northern Italy outlined in the EFI plots above. The plot includes ENS (blue), HRES (red dot), ENS control (purple dot), observation (green) and model climate (red).
3.4 Monthly forecasts
The plots below show ensemble mean anomalies for precipitation 28 Sept to 4 October from extended-range forecasts with different initial times.
The plots below show the same as above but for surface pressure anomalies.
