Closely following the tragic flood event in the “Cinque Terre” another severe weather event hit the Liguria region in late autumn 2011,after a remarkably hot summer and earl autumn that had caused significant positive Sea Surface Temperatures anomalies in the Tirrenian Sea.
Since many days ahead of the event both Global and Local Area Model started to show a increasingly dangerous set-up for the Genoa area: an area of strong convergence between “Tramontana” (wind from the North) and “Scirocco” (from the South-east) was forecasted for more than 20 hours, triggering regenerating-stationary thunderstorms, feeding from the large moisture in the low levels provided by the Scirocco wind.

In the “Storm Chasing” area of meteonetwork’s forum a team of citizen scientists had monitored the event from the first models’ outputs to the end of the flood and a chasing team formed to provide real time observations for the entire evolution of a such potentially devastating severe weather event.
The chasing team included Niccolò Ubalducci (Italy), Dean Gill, Oliver Staiger (Switzerland) and Marko Korosec (Slovenia). We met around midnight in Genoa, given the onset of the convection forecasted for the early morning. Once we got to the seaside we spotted the first lightnings that marked the start of a 20 hours long chase.

Probably due to the low moisture advection, caused by weak southerly winds, the thunderstorm was relatively weak during the first hours of its life-cycle; given the dominating northerly wind its motion was approximately towards south-east,
The chase has always been led on the southern edge of the thunderstorm where we had a better view on the cell’s structure.
The thunderstorm rapidly intensified around 3:30 am when it was near Portofino; as a consequence the first moderate floods occurred in the area between Recco and Rapallo. The cell remained almost stationary over Portofino for more than 4 hours, slightly weakening around 7:00 am.







[lightning storm in front of Portofino, 05 am]

While we were trying to monitor the localized flood in Rapallo we noticed a significant strengthening of the thunderstorm that, thanks to the increase of southerly winds in the low levels, started to migrate northwards approaching Genoa.
Following the thunderstorm we reached Genoa S.Ilario where we realized that the situation was getting even worse: from the promontory we observed the first, probably mesocyclonic, rain-wrapped waterspout.







Time-lapse video of the tornadic cell



A cyclic supercell, located along the convergence zone, was very likely embedded in the thunderstorm structure; from our video footage the structure clearly showed a strong rotation in the mid levels.
As the Scirocco increased at all levels the cell was located on the south-eastern part of the city: the cumulated rainfall was already over 200mm in that area and, with the updraft approaching the coastline, the rain rate increased significantly.
The first floods were reported in the city so we moved to Corso Italia where the intensity of rainfall and wind gusts prevented us from reaching the city centre.

We had to move back to Via Quinto where we observed the formation of two successive wall clouds, both showing strong rotation; the latter produced a mesocyclonic waterspout, accompanied by a strong RFD, that produced some damage in this area.




[developing waterspout approaching the coastline]




[strongly rotating wall cloud and associated funnel cloud, note the circulation already in contact with the ground (water spray on the sea cliff) ]

Around 2 pm the cumulated rainfall was extremely high (more than 500mm in Quezzi area) and severe flood was devastating the city centre, causing 6 deaths.

The motion of the mesocyclone along the convergence line at some point broke the equilibrium between Scirocco and Tramontana and the thunderstorm started to move towards WNW reaching the western part of the city.

This tragic day didn’t only show the vulnerability of an urban environment to such extreme weather events but also how the role of citizen scientists can be absolutely relevant in monitoring their evolution.

[copyright: all images belong to Niccolò Ubalducci]

Dear Meteonetwork colleagues,

i really like this contribution, it is very valuable from the point of view of better understanding this event, as well as impressive in showing how the cooperation with citizen scientists can be valuable not just from the data point of view.

We can really learn a lot more on the physics of the events using those images

Thanks!

more later

Hello

i found over the web this interesting talk

Szilagyi, W. A WATERSPOUT FORECASTING TECHNIQUE
(www.essl.org/ECSS/2009/preprints/O05-14-sziladgyi.pdf)

It is providing the necessary conditions for the occurrence of waterspouts.

I checked if with our "fine-resolution" (5-1 km) wrf runs those criteria are satisfied and this is really the case:

indeed DRIHM e-Science environment will enable also finer resolutions run (< 1 km) and data assimilation efforts thus we will be able to capture such conditions even better probably...

Stay tuned and we will provide an update!

Antonio

thanks Antonio for your appreciation,

I hope everyone in the DRIHM community had found it interesting and I'd be very happy to answer to any kind of question related to this post. It was just a very brief summary of a much wider series of discussions and contributions that involved Meteonetwork and its citizen scientists during the Genoa event.

It's very pleasing to see that the results of our work really mean something to the scientific community, it makes you see the whole point of being a citizen scientist.

I'm really interested in the paper by Szilagyi and I've also found a slightly different approach in waterspout forecasting (Kuiper and Van Der Haven,2007); even though I still haven't found a good description of how this technique works it seems it has been tested several times.

www.essl.org/ECSS/2011/programme/abstracts/7.pdf

elib.dlr.de/63558/1/s10-a.pdf


I think this could be expanded to multiple case studies regarding, for instance, Italy and I'm quite sure that data from our weather stations' network could play an important role.


Edoardo

Dear Edoardo

thanks again for your feedback, i fully agree with you. We think that there is a great potential into the citizen-scientists data, for example also for predictability studies concerning the forest fire risk.

I would like to interact with you and other citizen-scientists to define together the requirements for the DRIHM e-Science environment in terms of services useful for groups as Meteonetwork and similar ones

What do you think?

thanks a lot

best regards

Antonio