Autumn still seems far from conquering the scene. After a few cooler days and some rain arriving especially in the Centre-South, Italy is preparing to experience a new phase of anomalous heat: the subtropical anticyclone will in fact return to dominate the situation, bringing temperatures well above the average for the period, with peaks that could reach 30°C and, in Sardinia, even 32°C.
Autumn tries to make room for itself, but the anticyclone resists
The change of season continues to be postponed. The classic phase of bad weather that often accompanies the autumnal equinox, with the arrival of the first real Atlantic disturbances, has not yet occurred.
In recent days, some colder currents coming from the east have reported conditions more typical of the end of September, with rain and thunderstorms especially in some areas of the Centre-South. However, a parenthesis destined to be short-lived: as early as next weekend the meteorological picture will change again.
Blocking the arrival of autumn is a vast high pressure field over Western Europe, which prevents Atlantic disturbances from advancing towards the Mediterranean and favors the rise of warm air of subtropical origin.
The African anticyclone returns and Italy relives a tail of summer
The new expansion of the African anticyclone will bring masses of warm air towards the Peninsula, creating a decidedly unusual situation for the period.
Starting from Sunday 27 September temperatures will begin to rise again. The sun will once again be the protagonist and in many areas of Italy values close to 28°C can be reached, with local peaks around 30°C. It won’t be the intense heat typical of August, but the return of summer days at the end of September will still be evident.
The warmest phase could arrive in the first days of October. In the North, temperatures could remain around 28°C, while in the Center and South they could reach 30°C, especially along the Tyrrhenian areas. Sardinia could be the most affected region, with values of up to 32°C in the western inland areas.
A huge block of high pressure over Europe
The situation does not only concern Italy. Much of Europe will remain under the influence of high pressure, while Atlantic disturbances will be forced to flow towards more northern latitudes without being able to bring about the real change of season.
It’s a pattern that has characterized the continent for weeks now: persistent high pressures, above-normal temperatures and rains that continue to be postponed.
The turning point could come in October, but uncertainty remains
The first signs of change could appear between September 30th and October 1st, when new cooler currents could affect Southern Italy and Atlantic disturbances could try to enter from the western part of the country.
The return of more widespread rains, however, could be delayed further and only arrive in the first week of October. Forecasts at this time distance must in fact be interpreted with caution, because it is precisely the turning points announced many days in advance that are most often downsized or moved.
Because the change of time is continually postponed
When weather models indicate a possible turning point ten or twelve days away, they are not describing an already certain event, but a possible scenario.
Forecasts arise from the processing of millions of data collected every day by satellites, weather stations, sounding balloons, airplanes and ocean buoys. This information is used by supercomputers to reconstruct the state of the atmosphere and simulate its possible evolution.
The problem is that the atmosphere is an extremely complex system and even small variations in the initial conditions can produce large differences in the final result. It is the principle known as the butterfly effect: a small change at the beginning can profoundly modify subsequent evolution.
For this reason, meteorological centers do not develop a single forecast, but create various possible scenarios by slightly modifying the starting data. The further away we go in time, the more these scenarios can diverge.
A disturbance expected in several days could therefore only be one of the possibilities and not necessarily the one that will materialize. Even very large anticyclones can prove more resistant than expected, pushing the end of the heat from day to day.
Long-term forecasts indicate a trend, not a certainty
Beyond ten days, forecasts cannot accurately establish what the weather will be like in a single city. They serve above all to understand what the general evolution could be: whether high pressure or unstable conditions will prevail, whether cold currents or milder air will arrive.
For this reason, the new phase of unseasonal heat should be seen as a probable trend for the next few days, while for the true return of autumn we will still have to wait for updates to the meteorological models.
