Genoa – An intense prefrontal phase with abundant rainfall and hydrological criticalities affected, for many hours, the Savona hinterland and the Stura Valley. From the afternoon on, the whole region will be affected by the passage of the real perturbed front with showers, thunderstorms and gusts of wind that are particularly intense and to which to pay the utmost attention.
In light of the current situation and the latest modeling releases, Arpal has reshaped the weather alert for thunderstorms and widespread rains. These are the details:
Zone A (west): orange on small and medium-sized basins until midnight today, Monday 4th October. For large jungle basins, always until midnight today
Zone B (central region): red on small and medium-sized basins until 6am tomorrow, Tuesday 5 October, then yellow until 3 pm (in zone B there are no large basins)
Zone C (east): orange on all basins until 13 tomorrow Tuesday 5 October, then yellow until 3pm
Zone D (western Po slopes): red on small and medium-sized basins until 6 tomorrow morning, Tuesday 5 October, then yellow until 3pm. For large basins, orange until 6am tomorrow then yellow until 3pm.
Zone E (eastern hinterland): orange on all basins until 8 am tomorrow, Tuesday 5 Oct, then yellow until 15
In the next few hours, the intense perturbed system that the forecasting models identified a few days ago is expected on Liguria. It was preceded by a full-bodied prefrontal phase that involved the Savona hinterland and the Stura Valley and determined by the convergence between very humid sirocco winds and a weak, cooler and drier northern flow.
The precipitations, also enhanced by the orography, persisted in the same area for several hours with very high cumulations: aAt 12.30 the accumulated in the last 12 hours see Montenotte Inferiore with 550.4 mm (145.2 in an hour), Rossiglione with 520.4 mm (91.4 in an hour), Sassello with 352.6 mm (84.0 in an hour), Mallare with 245.4 ( 97.4 in one hour).
The phenomena were reflected in the responses of the watercourses: the hydrometric levels in the instrumented sections of zones D and B highlighted sudden rises and even exceedances of the second guard threshold, in particular as regards the Letimbro in Santuario di Savona . the Bormida di Spigno in Ferrania (Cairo Montenotte); near the second guard level the Bormida di Pallare in Carcare, and the Bormida di Spigno in Piana Crixia.
Now the transit over our region, from the afternoon, of the low pressure area called “Christian” * is expected: it will be a very slow passage, which will involve Liguria from West to East, with rains that will be more widespread than the localized phenomena of the morning, but still strong and with storms that are still intense.
Very strong hailstorms and gusts of wind will also be possible; it is not excluded that “downburst” phenomena may occur.
The weather alert in detail
Here is the detail of the phenomena expected for today, tomorrow and the day after tomorrow, contained in the meteorological warning issued by the Arpal Hydrological Weather Functional Center:
Today, Monday 4 October 2021: the transit of an intense frontal system determines up to very strong precipitations, also of a reverse or thunderstorm character, more insistent on the Center-West of the region. Cumulated up to high on all areas, intensities up to very strong. High probability of strong, organized and persistent thunderstorms on ABD and in the evening also on CE. Strong southerly winds, up to gale on BE, intense gusts possible in correspondence with thunderstorms. Sea rising everywhere, with storms on C especially from the evening.
Tomorrow, Tuesday 5 October 2021: gradual removal of the frontal system with residual bad weather in particular on the Levant. Widespread rains on CE with high probability of strong thunderstorms until central hours, even persistent on C until morning. Residual instability elsewhere with low probability of strong thunderstorms. Strong south-westerly winds on BD, also stormy winds on ACE with further intensification from the afternoon. Agitated or locally very rough sea, with south-westerly storm surges on AB, even intense ones on C with possible crossed wave motion in the morning.
The day after tomorrow, Wednesday 6 October 2021: the approach of a new perturbation from the North-West determines an increase in instability in the Center-Levant, with low probability of strong thunderstorms (possible localized flooding due to rainwater disposal systems or small canals / canals. punctual damage due to isolated gusts of wind or tornadoes, hail and lightning, small landslides. Civil protection reminds you to observe the appropriate self-protection rules). Northerly winds strengthening on ABD with more intense gusts from the evening.