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September 22, 2020 Today, September 22, autumn officially begins with the equinox scheduled for 3:31 pm Italian time.



The astronomical event will be greeted by the passage of a small asteroid and the Moon, with the international night dedicated to its observation, scheduled for 26 September.



The autumn equinox occurs when "the Sun in its apparent motion along the projection in the sky of the Earth's orbit (ecliptic) crosses the celestial equator from north to south, which is the projection into the sky of the terrestrial equator" explains astrophysicist Gianluca Masi, head of the virtual telescope.

This, he adds, "is the opposite behavior with respect to the vernal equinox where the Sun, always on that same apparent trajectory, instead passes from South to North. So for us who live in the Northern Hemisphere it means that the Sun goes down in the southern half of the sky, to the South, and as a consequence it will begin to remain above the horizon for a time that is less than the length of the night ".



In the southern hemisphere, however, Spring begins tomorrow.

Furthermore, on the day of the equinox, the stay of the sun on the horizon will be exactly half day, that is 12 hours, justifying the name of the astronomical event which derives from the Latin words Aequus, which means equal, and Nox, which means night. .

The date of the autumn equinox, adds the astrophysicist, is not always the same, but it oscillates between 21 and 24 September: "this phenomenon is connected to the leap year mechanism which reminds us that under the calendar structure there is it is the motion of the Earth which, to orbit around the Sun, obviously does not take exactly 365 days, but an extra fraction so that every 4 years in the calendar a day is added to February ".

The equinox, concludes Masi, "will be greeted by the close passage, scheduled for the morning of September 24, of a small asteroid with a diameter of a few meters that will arrive about 27,000 kilometers from the Earth and from the international night of the Moon, the initiative of NASA scheduled for September 26, of which the virtual telescope is one of the international supporters ".



The weather forecast


Italy is about to fall, therefore, in the middle of autumn.

In the next few days, summer will give way to a series of perturbations typical of the autumn season which, driven by southern winds and fed by fresh air, will cause rainfall at times abundant, but not only rainy.

In fact, between Friday 25 and Sunday 27, a cyclonic vortex filled with cold polar air will plunge into the Mediterranean causing temperatures to drop which, from the above average of these days, will sink below the norm of almost 7 degrees centigrade.



And with the cold, the snow will also arrive early.

Snow in September is not entirely a rarity, already in 2017 and again 2015, 2011 and then 2010 and 2007 the white lady whitened many places below 1400 meters (such as Cortina d'Ampezzo for example), but it is still a noteworthy event.

The entry of freezing currents expected with the intense perturbation of Friday 25, in addition to the thermometers will also cause the freezing point to collapse which will be around 1700 meters in the Alps.



But not always (indeed, rarely) the freezing level corresponds to the snow level (i.e. the altitude at which it will snow), so the white flakes between the early hours of Saturday and Sunday could drop below 1300 meters, especially close to the Alpine borders. 



Tuesday 22. In the north: unstable with precipitation almost everywhere.

Center: showers and thunderstorms over the Tyrrhenian regions, Umbria and Marche, local in Abruzzo.

In the South: rains in Sicily and Salento, more sun elsewhere.

Wednesday 23. In the north: more rain in the Alps, Prealps and Northeast.

Center: disturbed in Tuscany, Umbria and Lazio.

In the south: rains on inland Sicily and Salento.

Thursday 24. In the north: from good weather to heavy rain from afternoon / evening.

Middle: it gets worse in Tuscany in bad weather, more sun elsewhere.

South: sunny.

From Friday bad weather from the central north to the south, thermal drop.