Starting from Saturday 5th July The weather will grant a brief respite – in the form of a drop in temperatures and rainfall – to heat bubble With intense heat and heat that hit Italy in recent days with the arrival of the promontory of the North African anticyclone, journalistically – but improperly – nicknamed “Anticyclone Pluto”. In recent days we have heard from many sides to appoint “Pluto” As responsible for the torrid or sultry heat that has been gripping Italy for days. You will perhaps remember that last July there was talk in the same terms as “Caronte”another suggestive nickname to indicate the cause of the heat wave of the past few days. The journalistic tradition of giving a name to these phenomena can however lead to a certain confusion. So let’s see what we talk about exactly when we talk about Pluto and explain from a meteorological point of view because it is causing a wave of heat, because the heat lasts so long and because on the weekend we will have a respite with high temperatures.
Thunderstorms on the weekend and then lower temperatures: the forecasts
The anticyclonic field that is bringing high temperatures throughout the peninsula is already weakening: it will persist until you ask, and then allow already in the morning to Saturday 5th July to temporal lines from central Europe to infiltrate our country bringing a gradual drop in temperatures from north to south and thunderstorms first along the Alpine arc, then in the northern regions and finally in Central Italy. According to experts’s forecasts, the instability on our peninsula will last up to Wednesday 9 July When the temperatures return to rise without however reaching the peaks this week.
What is really “pluto” from a meteorological point of view
This confusion takes place mainly because giving a name to the heat waves recalls the way we speak for example hurricanes and in general of tropical cyclones, which instead have official names established by special organisms of the World Meteorological Organization.
Because if it is true that every hurricane is in all respects a meteorological entity in its own right, the same does not apply to “Pluto”, “Caronte” and any other “African anticyclone” that we hear about. This is because the heat waves that arrive in Italy in summer are not caused every time by a different African anticyclone: There are not many African anticyclones Each with its birth, its evolution and its death. North African anticyclone is only one And it is almost permanent above the Sahara. Technically what comes to us is not even an anticyclone in the strict sense, but a anticyclonic promontory: we can imagine it as a “protuberance” that appears from the North African anticyclone – recalled by areas of low pressure north – and extends over our peninsula and other parts of Europe. These promontories extend, weaken and then withdraw in the Saharan subtropical anticyclonic field.
The anticyclones are high -pressure high -altitude fields that form a closed -ended structure. The high pressure at altitude “crush” the air close to the ground, warming it: for this reason the anticyclones bring the heat. Furthermore, the anticyclones are associated descending currents That, once you arrive on the ground, they “spread” in all directions by effectively constituting a barrier that prevents the entry of cold air and disturbances. That’s why With the arrival of an anticyclone you generally have good weather (although, indirectly, heat waves can cause bad weather). What is bringing the heat to Italy in these days – that is, what we call “Pluto” – is therefore not an anticyclone but an anticyclonic promontory of North African origin extended on the European continent.
Because the heat wave caused by “Pluto” lasts so long
This configuration may seem very unstable, but it is not, and we are realizing it: hot and heat last for days now without interruption. This is no coincidence, indeed it is typical for the North African anticyclone cause rather prolonged heat waves.
This happens because the extension of the anticyclonic promontory for thousands of kilometers in the European continent is associated with that phenomenon that meteorologists call atmospheric block. Saharan hot air is recalled by two low pressure areas, a western call depression of Iceland It is an oriental that comes from Russia. At this point, on a synoptic scale, the promontory is “blocked” between these two cyclonic regions and the pressure configuration remains almost motionless for many days before the promontory “weakens” gradually. By “weakening” we mean that the descending currents that prevent the arrival of cold air and disturbances of vigorosity. At a certain point it happens that cold currents can overcome in intensity those associated with anticyclone, and then The anti -cyclone “wall” gives way. This is exactly what will happen starting from Saturday in Italy: the margin of the anticyclonic promontory will be won by the storm lines and cold air from the north, giving rise to instability on the days of the weekend and in the first days of the following week.
