The Sub-Polar Front has begun to exert a strong influence on the weather, marking the end of summer 2024.
Until recently, summer seemed able to resist the incursions of cold air from the North Atlantic, but recent developments indicate a clear change.
The weather forecasts for September are full of surprises, with summer now about to give way to cool and unstable currents.
The first sign of this change was the arrival of a disturbance from the North Atlantic, which brought heavy rains to various parts of Italy. Northern Italy, some areas of the Center, and Campania were particularly affected, with a significant drop in temperatures, down by about 6-8°C compared to previous values.
Precipitation in some areas exceeded initial forecasts, leading the weather scenario towards a phase of instability.
Next 36 hours: A drastic change
Within the next two days, a significant worsening of the weather is expected.
A core of cold air from the Norwegian Sea will move towards Italy, causing a drastic drop in temperatures, by about 10-15°C.
This cold air mass, separating from the main North Atlantic flow, will position itself between Italy and the regions of the former Yugoslavia, prolonging a period of instability with frequent showers and thunderstorms.
The most affected areas will be Romagna, Northeast Italy, the mid-lower Adriatic, and some southern areas of the peninsula.
Forecasts for the second half of September
The forecasts for the rest of September highlight an irregular distribution of rainfall in Italy.
The regions of Northwest and Western Tuscany could record a precipitation deficit, despite having recently experienced a surplus.
On the contrary, the areas of Northeast, Center, and Southern Italy could see an increase in rainfall, up to 40-50% more than the seasonal average.
The Main Islands – Sardinia and Sicily – should remain in line with usual rainfall values.
Thermally, the temperature drop will be significant across the peninsula, with decreases of 4-8°C compared to the average values for the period.
On the Apennines and the mountains of the Main Islands, the drop could reach 10-15°C, while in the central-eastern Alps the reduction will be even more drastic, reaching 15-18°C.
Snow could fall down to 1100 meters in the northeastern sector of the Alps.
Towards the end of the month, temperatures will likely return to average seasonal values, although a final return of the heat is not excluded.
However, the anomalous cold will continue to be a predominant feature until new meteorological developments confirm or deny further changes.
September 2024: A climatic reversal
September 2024 marks a clear reversal of the trend compared to recent years.
Usually, the month of September is characterized by a prolongation of summer, with hot and dry days.
This year, however, the influence of North Atlantic currents and the Sub-Polar Front has put an end to this trend.
Weather forecasts indicate that Italy will experience a drop in temperatures well below average, with scenarios more reminiscent of October or November than September.
The main cause of this drastic temperature drop is the arrival of a polar air front that will hit Italy in the coming weeks.
This will not only lead to a drop in temperatures but also an increase in instability phenomena, such as rain and thunderstorms, which will mainly affect the regions of Northeast and Central-Southern Italy.
Weather: End of September and early October
Towards the end of September, a further change in weather conditions is expected.
After a period of anomalous cold, temperatures could gradually rise, with the return of the anticyclone and warmer weather.
However, this change will not be sudden, and the heat will not reach the extreme levels that characterized the beginning of the month.
It is expected that temperatures could return slightly above the seasonal average, in a scenario reminiscent of the typical “September Summer.”
This new weather reversal is not expected before September 20, as until then Italy will remain under the influence of a depression circulation.
Forecasts indicate that the return of the anticyclone and heat will occur between September 22 and 24, bringing stable conditions that could last until the first days of October.
Long-term prospects
The weather scenario for September 2024 shows a highly dynamic situation, alternating phases of anomalous cold and returns of moderate heat.
After an early September marked by heavy rains and a drastic drop in temperatures, the second half of the month could see a partial return to warmer conditions, especially towards the end of September and the beginning of October.
However, the weather conditions for this period remain uncertain, and further twists with the arrival of new disturbances from the North Atlantic cannot be ruled out.
This year’s early cold nevertheless represents an exception compared to the last 15 years and could mark the beginning of an early and particularly harsh autumn season for Italy.
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