Storm Alex

{{Short description|Extratropical cyclone in October 2020}}

{{Infobox storm

| name = Storm Alex

| image = Storm Alex 2020-10-02.png

| caption = Storm Alex making landfall in Brittany at peak intensity on 2 October

| type = Extratropical cyclone
European windstorm

| date formed = {{Start date|2020|09|30|df=y}}

| dissipated = {{End date|2020|10|03|df=y}}

| maximum amount =

| fatalities = 16 fatalities

| lowest pressure = 969

| power outages = 115,000

| gust = {{convert|116|mph|abbr=on|order=flip}} at Belle-Île, France

| damages =

| areas affected = United Kingdom, Spain, Portugal, France, Italy, Austria, Poland, Czech Republic

| enhanced =

| fujitascale =

| tornadoes =

| tornado duration =

| partof = the 2020–21 European windstorm season

}}

Storm Alex was a powerful early-season extratropical cyclone that was particularly notable for its extreme flooding around the Mediterranean. Alex caused widespread wind and flooding damage across Europe, and at least 16 fatalities, with one more person missing{{update-inline|date=January 2025}}. Alex was the first named storm in the 2020–21 European windstorm season.

Originally, a minor low-pressure system to the south west of Greenland late on 27 September.{{cite news |title=Sun, 27 Sep 2020|url=https://www.wetterzentrale.de/en/reanalysis.php?map=1&model=cfsr&var=1&jaar=2020&maand=09&dag=30&uur=1800&h=0&tr=360&nmaps=24#mapref|access-date=9 October 2020 |publisher=Wetterzentrale.de |date=27 September 2020}} This pressure system tracked south eastwards, experiencing the Fujiwhara effect and then undergoing explosive cyclogenesis before making landfall in Brittany on 1 October. It was named by AEMET and Météo-France on 30 September, with Red warnings being issued for wind for parts of Northern France from 16:00 CET on 1 October.{{cite tweet|language=fr|author=Météo-France|user=VigiMeteoFrance|number=1311682638915276802|title=1 dpt en #vigilanceRouge ; 8 dpts en #vigilanceOrange |date=1 October 2020|access-date=3 October 2020}}

The storm led to advection of Mediterranean air northwards where it interacted with the coastal topography producing an extremely heavy rainfall in southeast France, known as a "Mediterranean Episode". This brought record breaking flooding and devastation to many areas in the region.{{cite tweet |user=WMO |number=1313443439141359616 |date=6 October 2020 |title=500 mm of rain fell in southern France on Fri-Sat during a "Mediterranean episode" triggered by #StormAlex. }}

The flooding in the south of France was purportedly the worst for at least 120 years, when records began.{{Cite web|title=2 missing after worst rainfall in 120 years triggers flash flooding in southern France|url=https://watchers.news/2020/09/21/flood-france-september-2020/|access-date=5 October 2020|website=The Watchers|date=21 September 2020 }}