Thunderstorm Warning: Warning in the West – Panorama

The sentence uttered by North Rhine-Westphalia’s Home Secretary, Herbert Rolle, sounds a bit like warnings from governors or the president if another hurricane hits the country in the United States. “Please stay home,” Roel says. “Avoid spending time outdoors.”

It can become violent. NRW is bracing for severe storms that are expected to hit the state Friday afternoon. In many places, schools close before 12 noon on Friday, and zoos and cemeteries are closed as a precaution, as in Cologne. On the warning map on unetterzentrale.de, around 3 pm, only parts of the Lower Rhine are colored red, the second highest category. But this may not remain the case.

This year’s deadliest storm so far is moving over Germany. Meteorologists from the German Weather Service (DWD) have warned of severe storms, especially in the west of the country. As of Friday afternoon, there was a risk of severe thunderstorms and torrential rain in some areas of up to 40 liters per square metre, particularly in North Rhine-Westphalia and Rhineland-Palatinate. You also have to take into account hailstorms and hurricanes, which are about 120 kilometers per hour, which equates to the strength of twelve winds. There can be isolated tornadoes. All in all, an “explosive mixture,” according to DWD.

The situation brings back unpleasant memories of the flood disaster nearly a year ago, which caused massive damage, especially in North Rhine-Westphalia and Rhineland-Palatinate, and claimed more than 180 lives. This has sparked a debate about how well or poorly Germany’s alarm systems work. The question many ask themselves: have the authorities and weather services learned from this?

Lessons learned from the Ahr Valley disaster

“Yes, we learned from him,” says Lothar Kirschbauer. He is a professor of urban water management and hydraulic engineering at the Koblenz University of Applied Sciences and worked as a reconstruction consultant after the July flood disaster. On the one hand, societies are now more aware that the responsible authorities in the event of a major storm are in close contact with each other. Flood prevention concepts are worked out across districts and there are on-site visits to identify local problems. “The municipality of Swisttal, where I live, checked, for example, at critical points whether street drains are free,” says Kirschbauer. “There is a strong awareness here in the area that we have to do something, both in the administration and among the citizens. Media events where homeowners can see what they can do to protect themselves from floods will be very well received.

Kirchbauer’s colleague Robert Leubner, who studies hydraulic engineering and water management at the University of Applied Sciences in Kaiserslautern, has noticed generally greater awareness among officials in North Rhine-Westphalia and Rhineland-Palatinate. But he also points out that thunderstorms such as the one threatening Friday cannot be compared to the afternoon movement flood last July. “These are two completely different things,” says Leubner. The Ahar Valley disaster is incorrectly associated with heavy rain, but in fact it was a typical river flood in a low mountain range region, i.e. it occurred over a longer period of time with a large-scale expansion, where large amounts of water flowed.

According to Guebner, unlike July in Ahr, thunderstorms that occur in a very limited manner do not require large cross-regional crisis teams. However, it is always important that the entire warning chain is intertwined, from meteorologists to water management to lifeguards and administrations. “The work of the meteorologists is over when it rains on the ground,” says Leupner. “And then we hydrologists only start working.” The consequences of a storm depend largely on current local conditions, such as how much water the soil can absorb. The same amount of rain can be catastrophic in one place and harmless in another.

In order to better prepare for disasters, the Minister of the Interior of the state of North Rhine-Westphalia, Ryol, has developed a 15-point plan. It provides for the creation of new coordinating bodies where the threads meet in emergency situations. Including the Crisis Response Unit and non-police department staff. “In a way, it’s a state-owned crisis response center,” Roel says. In addition, the state government wants to rely on digitization in order to enable a reliable “state of the state picture”. By changing the law, direct interference in radio broadcasting should be possible if necessary, as is already the case in Bavaria, and the provinces should improve their disaster protection planning. All metrics look good on paper, but their effectiveness will likely only become apparent when the next devastating storm hits NRW.

Difficult forecast for thunderstorms

Can people in areas affected by thunderstorms be warned in time? The general weather condition is already clear a few days ago. However, it is difficult to predict exactly where the lightning and thunder will be at a particular time. Predicting accurate thunderstorm cells is among the most difficult tasks for meteorologists.

Andreas Friedrich, press spokesperson and Tornado representative from DWD explains.

The Department of Women’s Affairs (DWD) can issue short-term warnings that are so accurate that they affect a single municipality with a maximum of 1.5 hours’ advance notice. Friedrich calls the area five to 90 minutes before a thunderstorm, which common rain radar applications often cover as well, the “Now Casting Zone.”

In Germany, DWD has access to a nationwide radar network system. “Our radars instantly recognize when heavy rain or hail forms in the cloud. We measure the strength of the precipitation particles, the direction of movement and whether there is a trend, that is, whether the rain and hail are condensing or not.” The direction of the displacement can be calculated from several “detections”, as Friedrich calls it, that is, whenever the radar detects a thunderstorm cell, you have an approximate path along which the storm will move. Although the word bahn is not actually correct, it would be more correct: cone. “The higher the forecast in the future, the wider and wider this cone. After 90 minutes it is no longer a municipality, but maybe half a district. And then you don’t know whether it will hit the far left place in the center or the right,” says Friedrich.

It is almost impossible to determine the initial point at which lightning and thunder first appear. “They already have hail on their heads before it can be seen on our radar image,” says the DWD meteorologist. In addition, thunderstorm cells can deviate or stop suddenly. “The forecasting tool does not offer 100% certainty,” Friedrich says.

Thus only a very rough range can be determined in which thunderstorms can fall, but you don’t have to. to Ermelende, That is the name of the bottom moving across Germany on Friday, Friedrich assumes a potentially affected area extending in a north-south direction from Saarland to northwest. The storm should then move east through the central federal states to Berlin and Brandenburg.

What does the warning string look like

The German Meteorological Service is legally obligated to issue warnings in critical weather conditions. The individual regional centers of the Social Welfare Administration coordinate with each other and with the Center in Offenbach. These warnings go, for example, to cities and communities, ministries of the interior, fire brigades, technical relief organizations, police, radio and television stations. Across Germany, tens of thousands of recipients receive warnings by e-mail – a kind of stormy newsletter. DWD also provides information about impending weather hazards on social media.

There are also warning apps like the Nina app for which the Federal Bureau of Civil Protection and Disaster Assistance (BBK) is responsible. According to the BKK, ten million people have downloaded it. Nina collects warning messages about various dangerous situations such as storms, fires, floods or explosive ordnance discoveries. Users can receive location-based warnings, which means they can freely choose locations within a radius of up to nine square kilometres, such as regions or communities, about which they will receive warnings on their mobile phone. All risks nationwide can be displayed on the map. The app also gives advice on what to do in an emergency.

According to the standards, a warning is given

DWD uses metrics to assess storm severity. There are four different levels of warning: from yellow for a simple weather warning, to orange (special weather), to red (severe weather). If the warning level is purple, a severe storm is imminent. According to DWD, this higher warning level is only issued about a dozen times a year.

There are separate measures for thunderstorm events as well as for storms and heavy rain. DWD has declared the highest warning level for thunderstorms, i.e. purple. The criteria for this are hailstorms, heavy rain and hurricane-like storms. The second highest warning level applies to wind and heavy rain. Here, the meteorological service warns of “hurricanes”, that is: winds starting from 120 kilometers per hour. On the heavy rainfall scale, the rate of precipitation per square meter per hour determines the severity of the event. With the currently announced “heavy rain”, rain falls from 25 to 40 liters per hour. At the highest warning level, it is more than 40 liters.

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