October 2018 N.E. Italy analysis

I have considered the data from Treviso airport (N.E. Italy) to sum up the monthly analysis (Figure1) in the N.E. of Italy.

The mean minimum and maximum temperatures (11.84/21.17 °C) have been considerably above the 1971-2000 average (8.8/18.9 °C). This is due to the continuous mild conditions especially between the first and second decade, with no cold spells during the whole month (Figure1) and numerous days with maximum temperatures above 20 °C and minimum above 10°C.

Figure1. Max and min temperatures Treviso October 2018.

In fact, the number of days observing maximum temperatures above 20°C is 22, with 15 consecutive days (in the first two decades) when the maximum values never fall below 20°C. Moreover, during this period, for 3 consecutive days the maximum values reached 24°C, almost 6°C above the climatological average, and, during the whole month, this values has been reached 6 times.

During the long period of very mild maximum temperatures, also the minimum values were well above the average, with 18 consecutive days observing minimum temperatures above 10°C, 5 consecutive days above 13 °C (almost 6°C above the climatological average). To notice that, even if the maximum values decreased during the intense rainfall event occurred in the last week of October, the minimum values stayed high due to the strong southerly winds blowing from the Adriatic Sea which caused still mild conditions and due to the continuous overcast conditions which have limited the radiative cooling at surface during the night.

The observed rainfall (135 mm) ,instead, has been above the average (92 mm). This is due to the intense event occured in Italy during the last week of October,which has caused floods in several areas. Thus, though the total observed rainfall is above the climatological average, it was not evenly distributed during the month, with 20 consecutive days (between the 6th and 26th) with no rain (anticyclonic conditions), and only 9 with observed rainfall, 6 of them consecutively during the last week of the month.

Figure2. Daily rainfall Treviso October 2018.


Italy: First cold spell of the season

Finally, the first cold spell of the season is reaching the Italian Peninsula.  As we can see in Figure1, easterly winds (Bora, Grecale) coming from the Balkans are blowing over the Adriatic sea, reducing the humidity and causing clear skies in the Po valley. However, these winds are causing the stau effect in Piemonte and Emilia Romagna, where overcast conditions occur. This is happening also along the peninsula, with more clouds on the east coast and bright conditions on the west.

Figure1. Satellite image of this late morning (Sat24).

The cold spell is causing (and will cause) a decrease in both minimum and maximum temperatures, with snow showers especially on the Appennines (low-medium height) and bright (but chilly) conditions elsewhere. The temperatures will plummet especially in the North, after weeks of mild conditions, with minimum values probably observed between next Monday and Tuesday. In Figure2 is shown the comparison between the actual temperatures and the situation observed 24 hours ago (Friday).

It is clear how the main variation is observed in the Alps, Adriatic coast and Sardinia (decrease in 4-6 °C in 24 hours).

Figure2. Comparison temperatures recorded at 12 UTC on Saturday and Friday (Meteociel).