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On the last day of 2020, the first three of 2021 and the Epiphany will pass below the “red zone”, with the return of the limitations that characterized the Christmas holidays. But from an atmospheric point of view, what can we expect? Using the terms that have characterized the latest decrees aimed at limiting the spread of the covid, we can speak of a “gray area” for Romagna and a “white area” for Emilia. In fact, 2021 will start with new snowfalls also in the plains of the western sector of the region, while in Forlivese the white flakes will be seen only on the reliefs.
Pierluigi randi, Certified Meteorological Technician and Ampro Meteorologist (Professional Meteorological Association)How will the last hours of 2020 pass?
For days a great depression of North Atlantic origin has been established, which affects a large part of the European continent and the Mediterranean basin, maintaining conditions of general instability with cloudy passages alternating with temporary clearings. The cyclonic vortex is accompanied by masses of oceanic air, therefore humid but not cold, so temperatures, in general, will be slightly above the norm for the period. On Thursday we will have a day with intermittent cloud cover alternating with clear streaks, but no rain. Some fog cannot be excluded, at night and early in the morning, in the low areas of the plain.
With the new year, will the snow appear again in the flat sector of western Emilia, while in Romagna?
On the first day of 2021, the vast cyclonic circulation present on the European continent will direct a new disturbed impulse in our peninsula, accompanied by a deepening of the depression in the ground between the Balearic Islands and Sardinia in slow evolution towards the northeast. Therefore, the weather will tend to be moderately worse with some light and intermittent rains throughout the territory, especially between the afternoon and evening. The snow will turn white again in the west of Emilia, but it will not go any further, while in Romagna the amount of snow will be around 700-800 meters since the gentlest currents will act in the lower-middle strata.
In December, two snowfalls were observed on the plains of much of Emilia, while Romagna suffered softer ridges. Is it the year of last Atlantic winter that hasn’t been seen in several years?
For the moment it seems that it is, with a circulation regime characterized by strong pressure towards the North Atlantic and, therefore, incapable of protecting the central Mediterranean area; In this way, the polar or arctic marine currents have the green light towards central-western Europe, generating continuous jet depressions that then go towards the Peninsula. In this way, a type of humid, unstable climate prevails, sometimes rainy, but not cold.
So how will the remaining days before Epiphany continue?
The situation will evolve little until at least day 4, with the Mediterranean area still governed by low pressure circulations always fed by the descent of the polar or arctic sea air from the northwest, therefore with a general unstable and not cold climate. It is true that the Epiphany is possible a partial variation with the transfer of the high pressures towards the north of Europe, and therefore with the influx from the northeast of much colder air of continental origin, but that should be limited to affecting central Europe . In our territory it would change little and we would still be under fire from depressions coming from the Iberian Peninsula; but there is still great uncertainty about the trend of Epiphany.
Is it possible to draw a trend line for mid-January?
This type of climate will probably last until the middle of next month, although temporary and brief phases of cold cannot be excluded due to the intervention of the colder northeast air, but in general this meteorological regime seems to be able to last. several more days and also characterize the first part of January 2021.
How do you measure the reliability of this winter’s seasonal forecasts?
So far very good: in the October and November emissions, the models from the European center of Reading showed a December with temperatures close to normal in Western Europe and very mild in the rest of the continent including Italy, while it was estimated that the rainfall would be higher than normal. in the Mediterranean sector. In fact, it goes exactly this way, with Western Europe less hot and more subject to some cold outbreaks of polar maritime origin, and Central-Eastern Europe with a very mild month; Rainfall was also higher than normal, especially in the Mediterranean area.
There are those who exclaim about a particularly rigid February due to the consequences of the warming of the stratosphere expected in recent days. What is your opinion?
In reality, the sub-seasonal and seasonal scenarios always highlighted by the European center of Reading go in the opposite direction, with a rest of the winter marked by a prevailing regime of rather tense Atlantic currents, with pressures above the norm on Europe. south and lower in the north. This would lead to a mild but less rainy trend in Italy and the central Mediterranean basin than in the early part of winter. However, there are elements of particular uncertainty linked to stratospheric events, with a now very probable warming, which sometimes is transmitted to the lower altitudes of the Arctic region, weakening the polar vortex and developing anomalous high pressures prone to intense decreases in very cold air. to the south. The problem is that the transmission of stratospheric effects to the troposphere is not taken for granted (in fact, it is rare), and that it is not possible to know in advance where the cold drops will hit (US, Europe or Asia). If the dynamics in the stratosphere had some “minor” effect, we would have the reflections around the middle or third decade of January, but for now the numerical models are not of this opinion waiting for new updates.
