On these days in 2001.. torrential rains claim the lives of hundreds of people in Algeria

ArabiaWeather.com - Wael Hakim - November 2001 The history of a tragedy etched in the memory of Algerians after torrential floods that surprised many as they left their homes on the morning of Saturday, November 10, 2001, on their way to study and work.

Unfortunately, 733 citizens were killed, most of them in Algiers, in addition to hundreds of missing and huge material losses.

According to my eyewitnesses; Noureddine Sahraoui, an Algerian citizen from Algiers, lived through the events of the catastrophe. Between seven in the evening on Friday, November 9, and until one in the afternoon, on Saturday, November 10, more than 260 mm of rain fell over Algiers, i.e. approximately 3 times the rate of rain in Algiers during the whole month of November. During the 18 hours of precipitation, the rain intensified on Saturday morning, so that the Bouzareah station recorded 111 mm in just two hours. Therefore, the land was not able to absorb all this rain, so it turned into a torrential torrent coming from A high in the capital towards the cliffs and low areas, the blow was strong in the low neighborhoods of Bab Al-Wad, sweeping cars with their passengers towards the sea.

The formation of depressions in the Mediterranean is not something strange, but what happened during the formation of the depression is what made the situation exceptional, violent and catastrophic.

The extreme atmospheric regime that caused the disaster began with a deep and powerful depression over the Scandinavia region that moved steadily towards southern Europe and the western Mediterranean, accompanied by the flow of cold polar winds over all layers of the atmosphere, which led to a decrease in the atmospheric pressure from a value of 1006 hectopascal on Friday, November 9 to 997 hectopascal. During the day Friday, November 10, coinciding with the warmth in the waters of the Mediterranean.

The sharp drop in atmospheric pressure values led to a dynamic moisture convection towards the higher atmospheric layers cooled by polar air, which then led to very heavy precipitation.

In addition to what was mentioned previously, the thermal potential energy factor (cape) interferes with the strengthening of the air condition, and thermal energy is in the form of a latent present inside water vapor in a mass of air, when it is released outward “due to condensation” it is in the form of tangible thermal energy that raises the air temperature compared to With the surrounding air, which makes it very unstable and feeds thunder clouds and thunderstorms (strengthening its vertical movement a lot), the reason is that the condensation process releases tangible thermal energy and the evaporation process works to absorb heat, which is what happened during the November 2001 case, when the polar descent preceded a rise in The surface temperature over northern Algeria was the fuel for the case's ignition.

The complexity of the predicted weather situation and knowledge has increased only Maken However , many threat Spate is a n air condition interfered with local factors which represented the terrain, where he scored the western part of the capital , with the mountainous amount of rainfall was double that hit the eastern section of the capital with a character Sahli, as The proximity to the sea contributed to the increase in the intensity of precipitation.

The catastrophe of 2001 or the Bab El-Wad disaster, as the Algerians call it, despite the tragedies and sorrows that it brought with it, it is a lesson not only for Algeria to find solutions to avoid a repetition of the tragedy or at least reduce its damage, but it is a lesson for us as forecasters, as the situation carried with it circumstances and factors Rarely did it meet in one weather case, so the 2001 case became a rich topic of research in which we have many lessons and lessons.