Status: Ongoing analysis Material from: Linus, Thomas Haiden
1. Impact
On 5-7 December an extreme precipitation event hit south-eastern Italy and southern Austria. The event led to new records of 72-hour precipitation totals, e.g. 298 mm in Lienz (670 m, provincial capital of East Tyrol), where the previous record was 259 mm in 1966, and measurements go back to 1880. Similar values (between 250 and 300 mm) were observed at several stations in the area. The highest 72-h total of 364 mm was observed in the village of Kornat (990m) close to the Italian-Austrian border, but interestingly this was not a new record. In October 2018 this station measured 415 mm in 72 hours.
Since the snowfall line was quite variable during the event (varying between 500 and 1500 m both spatially and temporally) the snow was generally wet and changed temporarily into rain in the valleys. That is why in most of the affected areas, snow depth did not break any records, although values of 1-1.5 m were typically reached at lower elevations, and 2-4 m higher up.
On the Italian side 48-hour precipitation above 700 mm was measured.
2. Description of the event
The plot below shows snow depth after the event (from the Austrian met service).
The plots below show analyses of MSLP and 6-hour forecasts of precipitation from 4 December 00UTC to 7 December 00UTC, every 12th hour.
The plots below show analyses of z500 (contour) and T850 (shade) from 4 December 00UTC to 7 December 00UTC, every 24 hour.
3. Predictability
3.1 Data assimilation
3.2 HRES
The plots below show 48-hour precipitation on 5-6 December in observations (first plot) and short-range HRES forecasts.
3.3 ENS
The plots below show EFI for 3-day precipitation (5-7 Dec) from forecast with different initial dates (shortest forecast first).
The plot below show evolution of forecasts for 2-day precipitation (5-6 Dec) in 46N-47N, 11.5E-13.5E for HRES (red dot) ENS control (purple dot) and ensemble distribution (blue).
