BERLIN (NYTIMES) - Days before roiling waters tore through western Germany, a European weather agency issued an "extreme" flood warning after detailed models showed storms that threatened to send rivers surging to levels that a German meteorologist said on Friday (July 16) had not been seen in 500 or even 1,000 years.
By Friday, those predictions proved devastatingly accurate, with more than 100 people dead and 1,300 unaccounted for, as helicopter rescue crews plucked marooned residents from villages inundated sometimes within minutes, raising questions about lapses in Germany's elaborate flood warning system.
Numerous areas, victims and officials said, were caught unprepared when normally placid brooks and streams turned into torrents that swept away cars, houses and bridges and everything else in their paths.
"It went so fast. You tried to do something, and it was already too late," a resident of Schuld told Germany's ARD public television, after the Ahr river swelled beyond its banks, ripping apart tidy wood-framed houses and sending vehicles bobbing like bath toys.
Extreme downpours like the ones that occurred in Germany are one of the most visible signs that the climate is changing as a result of warming caused by greenhouse gas emissions.
Studies have found that such floods are now happening more frequently for a simple reason: A warmer atmosphere can hold more moisture, generating more, and more powerful, rainfall.
But even as extreme weather events become increasingly common around the globe - whether wildfires in the American West, or more intense hurricanes in the Caribbean - the floods that cut a wide path of destruction through Germany, Belgium, Switzerland and the Netherlands this week were virtually unheard of, according to meteorologists and German officials.
Even so, they were not unforeseen.
"There should not have been so many deaths from this event," said Dr Linda Speight, a hydrometeorologist at the University of Reading in Britain, who studies how flooding occurs. She blamed poor communication about the high risk posed by the flooding as contributing to the significant loss of life.
For now, German politicians have made a point of not wanting to appear to be politicising a calamity, and Chancellor Angela Merkel's spokesman said she planned to visit the stricken state of Rhineland-Palatinate, after returning from talks in Washington.
But the natural disaster had all the hallmarks of an event that has in the past reshaped political fortunes in German election seasons like this one.
Mr Armin Laschet, the conservative leader of North Rhine-Westphalia, who is vying to succeed Dr Merkel after national elections on Sept 26, told a news conference on Friday: "Our state is experiencing a flood catastrophe of historic scale."
"We have to make the state more climate-proof," said Mr Laschet, who is facing his strongest challenge from the environmentalist Green party. "We have to make Germany climate neutral even faster."
But his state was among the hardest hit. Once the floodwaters recede, he and Dr Merkel may yet face questions about why their political strongholds were not better prepared.
German officials said on Friday that their warning system, which includes a network of sensors that measure river levels in real time, functioned as it was supposed to. The problem, they said, was an amount of rain they had never seen before - falling so rapidly that it engorged even small streams and rivers not normally considered threats.
To describe the events of recent days as a 100-year flood would be an understatement, said Mr Uwe Kirsche, a spokesman for the German Weather Service, calling it a flood the likes of which had not been seen in perhaps a millennium.
"With these small rivers, they have never experienced anything like that," Mr Kirsche said. "Nobody could prepare, because no one expected something like this."
On Tuesday, Mr Felix Dietsch, a meteorologist for the German Weather Service, went on YouTube to warn that some areas of south-west Germany could receive previously unimaginable volumes of rain. Up to 70 litres, or more than 18 gallons, of water could pour down on an area of 1 cubic m within a few hours, he warned.
The weather service, a government agency, assigned its most extreme storm warning, code purple, to the Eifel and Mosel regions. It was one of numerous warnings that the weather service issued on Twitter and other media earlier this week that were also transmitted to state officials and local officials, fire departments and the police.
But the waters rose so swiftly, to levels beyond previously recorded record levels, that some communities' response plans were rendered utterly insufficient while others were caught off guard entirely.
A spokesman for the office responsible for monitoring floods and alerting local officials in Rhineland-Palatinate said that all warnings had been received from the weather service and passed along to local communities as planned.
But what happened after that is critical, and not entirely clear.
In the village of Musch, at the junction of the Ahr and Trierbach rivers, Mr Michael Stoffels, 32, said that he had gotten no warning from the government, but that a neighbour had called to alert him to the rapidly rising waters on Wednesday.
He rushed home from the retail store he manages nearby to salvage what he could. He was lucky, he said, since he has storage on the ground level and his living area is above that, so the 3.65m of water that his home took on did not cause significant damage.
But the village of 220 people got clobbered by flash floods that one resident, Ms Maria Vazquez, said wreaked havoc in less than two hours. On Friday evening, the village was without electricity, running water and cellphone coverage.
Across the border in Belgium, 20 people were confirmed dead, and 20 remained missing, Prime Minister Alexander De Croo said on Friday, calling the floods "the most disastrous that our country has ever known".
Waters rose on lakes in Switzerland and across waterways in the Netherlands, leaving hundreds of houses without power and submerging the city centre of Valkenburg in the Netherlands, although neither country suffered deaths or the destruction inflicted on German towns.
Mr Medard Roth, mayor of Kordel, in the state of Rhineland-Palatinate, defended the warning systems and said that he activated his town's emergency flood response once he had been alerted that the waters of the Kyll river were approaching dangerous levels. But the waters rose too rapidly to be held back by the usual measures.
"Already on Wednesday afternoon at 3.30pm, the Kordel fire brigade began setting up the security measures," Mr Roth told Bild, a German newspaper. "By 6pm, everything was already under water. Nobody could have predicted that."