2 Jun 2016

Europe floods: why has the rain been so intense?

Flash floods have hit parts of Europe in the last few days, leaving at least 10 people dead and more still missing.

Germany, France and Austria have been worst affected, with torrents of water flooding homes and businesses, damaging transport infrastructure and leaving thousands without power.

France has been particularly badly affected, with river levels in Paris rising to levels not seen since the massive flood that hit the city back in 1910.

Flood in Paris

Meteo France, the country’s national weather service, has issued its highest level red warning for flooding in the north of the country.

Heavy, thundery downpours of rain at not unusual across Europe during late spring and summer, so what has made this rainfall and subsequent flooding so intense?

Low pressure

Since the weekend, there has been low pressure across much of central and western Europe, which has low_pressure_MO_wpmade the air very unstable and prone to rising and forming clouds and rain.

Normally areas of low pressure move through on the jet stream, but this one has become detached from the jet stream and has become very slow-moving, affecting the same areas for days on end.

With plenty of potential energy in the air and some heating from the strong sun, heavy downpours and severe thunderstorms have been intense and widespread.

Moist, humid air

As well as low pressure, the wind coming from the south has dragged up very warm, moist and humid air humid_air_WZ_wpfrom the Mediterranean.

Moist, humid air has been a large contributor to the intense rain and floods, because it acts as fuel for the atmosphere – supplying a huge amount of energy on which storm clouds thrive.

For as long as the moist, humid air is present, the potential for thunderstorms will continue.

Prolonged rainfall

As mentioned already, the area of low pressure has been very slow-moving, which has meant that the same places have been prone to seeing stormy weather for prolonged periods of time.

With the presence of no or very little wind, severe thunderstorms have lingered over particular regions, dumping torrential rain in the same place, rather than over a more widespread area.

It’s the persistence of this intense rainfall that has subsequently overwhelmed drainage and river systems, leading to flash flooding.

Severe thunderstorms and lightning

Much of the intense rainfall has been generated from severe thunderstorms that have been widespread across Europe since last weekend.

In fact in the last five days, up until the end of 1 June, there have been an estimated 1.4 million lightning strikes across Europe, according to the lightningmaps.org website.

The map below shows lightning strikes from 28-31 May, illustrating just how widespread the severe thunderstorms have been.


How long will it continue?

At the moment, the risk of further heavy downpours of rain and severe thunderstorms will continue for at least the next few days – possibly into the start of next week.

With low pressure still across Europe and humid air still in place, the ingredients are there for more severe weather and a risk of further flooding.

The map below, showing a prediction of rainfall amounts for the next three days, suggests that there could be another 50-100mm of rain in places – indicated by the purple colours.


I’ll be keeping a close eye on the situation in the coming days and posting updates on Twitter – @liamdutton

Tweets by @liamdutton