Status: Finalised Material from: Fernando, Linus and Alessandro Fuccello (Italian Air Force Weather Service - CNMCA)
Discussed in the following Daily reports:
http://intra.ecmwf.int/daily/d/dreport/2013/11/13/sc/
1. Impact
Torrential rains and flooding hit Sardinia Island in on the 19 November, particular in the NE region. At least 17 people died as result of this exceptional weather. http://www.bbc.co.uk/news/world-europe-24996292
2. Description of the event
The downpours was associated with a low pressure system formed from a wave breaking ridge localized west of Iberia Peninsula last Saturday. The closed low moved slowly to east, producing very unsettle weather in western Mediterranean region.The northeast of Sardinia reported rainfall amounts exceeding 80 mm in 24 hours (of the station on GTS) and some other stations considerably more. The south of France also recorded amounts above 40 mm in several places.For several hours, south-easterly low level winds (humid) were constantly battering the mountains of the east coast enhancing the orographic precipitation.
The figure above shows the accumulated precipitation between 18 Nov 06 UTC and 19 Nov 06 UTC.
3. Predictability
3.1 Data assimilation
3.2 HRES
The short range forecast from HRES based on 17@12 shows the larger PPN amounts spreading along the east coasts of Sardinia and Corsica. For Sardinia the amounts exceed 81 mm in 24 hours. The maximum of precipitation did not occur here but to west in south of France near the Spanish border; the value exceeded 100 mm!
3.3 ENS
In general the ENS did a good job. The panels on the top of the slide show the EFI for precipitation valid at the same time starting 5 days before. The signal is quite high everyhere in particular for Sardinia/Corsica and south France but the later is less "predictable" five days in advance (see panel on the right). The bottom panels shows the probability that PPN exceeding 60 mm in 24 hours. This threshold is much higher than the 99% percentile model climate in both Sardinia and France. For Sardinia the probabilities reach 50% for day 3 but rapidly go down to 20% for longer lead times.
3.4 Monthly forecasts
3.5 Comparison with other centres
4. Experience from general performance/other cases
5. Good and bad aspects of the forecasts for the event
6. Additional material
Report about the case provided by Alessandro Fuccello (Italian Air Force Weather Service - CNMCA). Find the text here: Sardinia_Flooding.docx And the figures here: figs_itl.pdf