Storm in Mesolcina: «The worst is over, but…»

The violence of the storm that hit the Moesano area yesterday evening explained by Cecilia Moretti of MeteoSvizzera.

LOSTALLO – Mud, debris, swollen rivers and cars dragged by the current. The scene that appears the day after the storm that hit yesterday, Friday 21 June, with extreme violence on Mesolcina is apocalyptic. 24 hours after the storm, we are still looking for three people who are missing. A fight against time kept alive by the incessant work of the rescuers. Several dozen residents had to be evacuated from their homes, but most of them, the Graubünden police explained, were able to return to their homes this morning.

So much fear – However, the region is still shaken. The danger has in fact passed, but not the fear of a nightmarish night that no one would have ever imagined having to experience. A feeling conveyed by the testimonies of those who have seen death in the face. “It was scary,” a woman who was trapped in her home after a landslide covered the cantonal road with mud and stones told 20Minuti. «I never thought he could reach such fury. But this is nature.”

However, let’s now try to understand, with Cecilia Moretti of MeteoSvizzera, what weather conditions led to the storm. «Yesterday we had a disturbance pass through. It was a cold front that brought a lot of instability and an air mass with enough humidity to develop strong showers and thunderstorms”, the expert explained to us. «Several rainfall occurred throughout the day on Friday. A situation that has led to decidedly high accumulations.”

A water bomb – The quantity of water that hit the Mesolcina, in particular in Sorte, a hamlet of Lostallo, was impressive. «To understand the entire meteorological event we must analyze the quantities by adding the last twenty-four hours: we have had areas in which the hundred millimeters were exceeded». The reason for such a violent impact, however, is another. «These are precipitations that had high accumulations in a very short time. For example, from the first analysis of the data at the Grono station, sixty-three millimeters were measured to have fallen in one hour.” A fact that hasn’t been recorded for years. «In the specific case of Grono, the return period is between twenty and thirty years».

However, the storm was concentrated in a limited area. “There were many showers and many storms that followed one another in a short time.” An aspect that explains the significant damage recorded in the region. «We therefore had repeated rainfall that continued to hit the same area. The orientation of the flow in which these storm cells were inserted was almost parallel to the Mesolcina. This has led to significant accumulations in these areas.”

And now? – The worst now seems to be over. «However, we cannot say that the storm is completely over. We have another disturbance approaching at the moment with the first showers in upper Ticino.” This is a much less intense phenomenon than yesterday’s, «but it could disturb the work being carried out today. Because in any case some precipitation or isolated thunderstorms could still occur, especially this evening.” And tomorrow? «We will still have some precipitation, but it will mostly be showers. The intensity of the expected rainfall is certainly not to be compared to that of yesterday.”

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