In Arizonain the United States, about 39,000 people remained without current due to a storm of dust and sand that hit the city of Phoenix. The National Weather Service (the US government agency that deals with weather forecasts) specified that it was a “haboob”, That is one dust storm raised by the cold currents produced by an atmospheric front which, generally, is formed in conjunction with a storm in very arid regions or after long periods of drought. THE’airport international Sky Harbor It was temporarily blocked, with over 200 delayed or canceled flights, given that the dust wall has reduced visibility to a minimum causing heavy inconvenience also to car traffic.
What is the sandstorm that hit Arizona: the Habooob
As already mentioned, the Habors are powder storms that form in concomitance of thunderstormswhen the descending currents of the latter raise dust and sand from the ground. In particular, when a storm begins to download the rainthe temporal structure can generate intense calls also Downraft that, once the soil is reached, they can be propagated along the direction of progress of the temporal front. These currents, which can also reach i 100 km/hare intense enough to lift a mass of dust that extends well beyond the cloud of rain, up to 100 km in width along the temporal front.
In general, the Habors are formed in the regions characterized by dry landespecially during periods of drought. The problem is that, precisely in these more arid regions, the rain often does not have time to reach the ground because evaporate first (due to high temperatures). The effect of this phenomenon, called virgais twofold: firstly, the absence of rain prevents the dust raised from returning to the ground under the effect of the rainfall themselves; In addition, the evaporation of the rain steals heat in the air, cooling it and effectively accelerating the descendants that feed the haboob.
According to what reported by National Weather Servicethe Haboob would have formed starting from a temporal complex that developed north of Tucson (the second most populous city of Arizona after Phoenix), in the mountains of Santa Catalina.
Where the haboobs are more frequent and how long they last
In reality, this type of phenomena are quite common in USAespecially in the arid and desert areas of south-west of the United States and during the season of summer monsoons. Likewise, Habors can also occur in others arid regions of the world, like the desert of Saharathe Arabian peninsulaThe North Africa and the Gulf of Guinea.
Generally, Habooobs last between 10 and 30 minutes, although in rare cases they can continue for more time: in any case, its passage involves an almost sudden reduction in visibility, with consequent dangers for terrestrial transport and air traffic.
