This sudden change will be determined by a "greater dynamism of the atmospheric circulation", say the experts, linked to the arrival of a disturbance coming from the Atlantic. Specifically, it is an area of low pressure that will initially arrive in Great Britain and France and then in Italy, where it will bring a sharp drop in temperatures. From today the instability should extend to all the regions of the Centre-North, from Lazio upwards. The mass of cold air at high altitude will therefore collide with the warm air accumulated so far, causing several precipitations. Meteorologists expect "intense thunderstorms and gusts of wind and hailstorms cannot be ruled out: it will be a situation - Gozzini confirmed - to be followed in each region".
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What to expect next? On Thursday 10th the disturbance is also expected in all the Tyrrhenian and southern regions, in particular in Sicily, Campania, Puglia and Calabria. But the bad weather will not let go even in the Centre, on Lazio, Tuscany and Marche, while Piedmont and Lombardy should see some sunshine again. Residual thunderstorms are expected on Friday and next weekend again in the South, in Puglia, Calabria and Basilicata. "This substantial change could last until mid-September, but what will happen then remains to be seen," concluded Gozzini. "In recent years, September has been a summer month and there is still no evidence to rule out a hot end of September, with the return of temperatures above 30 degrees."
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Friday 11 September, as reported by the experts of "ilmeteo.it", despite a timid recovery in atmospheric pressure in the North, the day will still be characterized by a rather unstable atmosphere. Showers are expected above all in the central regions, while more localized phenomena may involve some areas of the North and several areas of the South. A sharp drop in temperatures will also begin to be recorded in the southern regions.
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The first signs of a recovery can be seen around the weekend, even if the situation will not yet be completely stable. Saturday the 12th may bring further instability, with the risk of some showers or thunderstorms in some areas of the country. The trend will however be that of a gradual improvement, although it will be necessary to carefully follow the evolution of the low pressure vortex and its effects on Italy.
The arrival of bad weather, as mentioned, also announces a whole series of alerts in the regions that will be affected. Arpal has issued, for example, a yellow warning for thunderstorms in Liguria, in the eastern center of the region from 8am to midnight on Wednesday 9 September. In the west, however, there is a low probability of strong thunderstorms. Scattered rain is expected, with strong thunderstorms also in the Central-East, followed by abundant and localized rainfall and local hailstorms. From the afternoon, winds are expected to strengthen to locally strong from the south-west along the western coast, from the south, south-west on the central eastern mountains with local thunderstorm gusts.
The Veneto Civil Protection, however, has declared an orange alert for thunderstorms and hydrogeological risk in some areas of the region. A yellow alert has been issued for other areas. The most intense phase of the hydrogeological warning for thunderstorms is expected starting from today morning. The alert will also continue on Thursday with a more intense phase at least until the central hours. Also today, experts predict greater instability with showers and thunderstorms at times widespread and probable intense and locally abundant phenomena, especially on the plain.
The Civil Protection of Friuli-Venezia Giulia has issued a yellow alert valid from 6am today to 6pm on Thursday for heavy rain, thunderstorms, including strong ones, and wind, expected across much of the region. In these hours, in fact, a trough will sink towards the western Mediterranean, resulting in the influx of rather humid and unstable south-western currents into the region. Scattered showers and thunderstorms are therefore expected, more likely and widespread from the afternoon. Some strong thunderstorms are also possible, especially towards the coast, with locally intense rain and strong gusts of wind. Heavy to intense rain is expected on Thursday, especially in the first part of the day and on the plains and coasts, where locally it could be very intense.
The effects of the arrival of a deep North Atlantic trough descending towards France which will lead to a worsening of the weather will also be felt in Piedmont. The first effects, reports ARPA, which has issued a yellow alert for thunderstorms with hail and gusts of wind, will be more evident in upper Piedmont up to the Lake Maggiore area, with moderate thunderstorms. In particular, showers and thunderstorms are expected especially in the valleys of the Cuneo area with intensification on the central-northern plains. The low pressure area will lean against the Alpine arc, bringing very humid and intense flows to Piedmont which will cause strong instability on the plains. Thursday will return to stable conditions, excluding scattered light showers close to the Apennine belt, in a context characterized by irregular cloud cover and falling temperatures, close to the averages for the period.
Based on available forecasts, the Department of Civil Protection has also issued a warning of adverse weather conditions. The warning predicts precipitation from today morning, mainly showers and thunderstorms, in Piedmont, Lombardy, Veneto, the Autonomous Provinces of Trento and Bolzano, Friuli-Venezia Giulia, Emilia-Romagna, Liguria, in particular in the central-eastern sector, and Tuscany. The phenomena will be accompanied by heavy showers, strong gusts of wind, local hailstorms and frequent electrical activity. On the basis of the foreseen and ongoing phenomena, the orange alert was assessed on the western sectors of Emilia-Romagna and on a large part of Lombardy and Veneto. Furthermore, a yellow alert has been assessed in Trentino-Alto Adige, in Umbria and in sectors of Valle d'Aosta, Piedmont, Liguria, Lombardy, Veneto, Friuli-Venezia Giulia, Tuscany, Emilia-Romagna and Calabria.
Meanwhile, in these hours and precisely because of the arrival of bad weather, the Metropolitan City of Milan has ordered "highly urgent interventions" to speed up the reclamation of the Naviglio Grande where a trail of hydrocarbons has spilled along a 28 km route. Vehicles and teams have already started work to vacuum the material that had been confined in order to avoid the risk that the rains could spread it, compromising what has already been done and to avoid downstream effects in the territories of Robecco sul Naviglio, Corbetta and Cassinetta di Lugagnano.
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