Genoa low Rolf

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Rolf (NOAA 01M)
Rolf (NOAA 01M)
Tiefkern Rolf , Ligurian Sea, November 8, 2011
General weather situation Mediterranean depth ( heavy rain event )
Storm Medicane ( hurrican -like Mediterranean low; hurricane force )
Data
Climax 4-8 November 2011
Air pressure [min] 991 hPa [mbar] (NOAA / Dvorak, 8.11. )
Wind [peak / 1 s] 122 km / h (deep core)
Precipitation > 600 mm / 72 h (Ligurian coast, the sixth-11.8. )
Annuality (total) approx. 5 / max. 50 (weather situation / Genoa 1970)
consequences
affected areas Northern Italy , Le Midi
Victim 11 (6 Italy, 5 France)

Rolf was called a genoa low that led to severe flooding in north-western Italy and southern France in the first week of November 2011 . The low also became prominent in specialist circles because it was reported by the American weather agency NOAA as a hurricane-like cyclone .

At least 11 people were killed by the effects of the storm, most of them in flash floods , in Genoa in the Italian region of Liguria and in the French department of Var .

weather condition

In the first week of November, a draft of cold air over the Iberian Peninsula developed into a low pressure area between the Balearic Islands and Corsica , which developed into an extraordinary storm system over the Ligurian Sea , which NOAA ascribed tropical storm-like properties on November 7th, but what does not really apply to Mediterranean lows.

The low was blocked by the mighty Russian high Walli (> 1040 mb). A strong southerly current developed from the Central Sahara, which caused the Genoa Low Rolf to get stuck in the Ligurian region and not create a Vb-like trajectory to the east.

Like all European low pressure areas, the system was named as part of the weather sponsorship campaign of the Free University of Berlin . The system created on November 4th was named Rolf . On November 7th at 6:00 p.m. UTC, NOAA classified the system as tropical and assigned the designation 01M , whereby the numbers correspond to the counting of tropical systems in the current year, analogous to other basins, and the letter represents the identifier for the Mediterranean.

course

Track of the storm

The Satellite Services Division of the US National Oceanic and Atmospheric Administration classified Rolf as a tropical disturbance on November 7th at 12:00 UTC. Six hours later, the satellite image evaluations showed that the deep convection in the circulation center of the system had existed long enough to classify the system as a tropical storm. At midnight on November 8, NOAA announced that SSMIS data had been used a few hours earlier to determine that Rolf had an eye-like feature. During this phase, NOAA determined a value of 3.0 using the Dvorak technique , which indicates continuous one-minute wind speeds of around 45 knots and a central air pressure of 1000 hPa. The storm initially maintained its intensity, but six hours later the convection began to decline and, with the exception of the northeast quadrant, the center was almost completely detached from the convection. At 6:00 p.m. UTC, NOAA noted an increase in convection, drawing more around the center. but by midnight the storm had weakened significantly and the convection had largely dissolved.

From November 4th, there was heavy precipitation (over 600 mm / 72 h in Liguria; long-term monthly mean November for Turin about 70 mm, 936 mm / 5 d in Valleraugue in the Alpine Alps , a six-month normal precipitation), thunderstorms and Hurricane-like wind speeds of up to 122 km / h and abnormally high seas on the Cote Azur (around 2.5 m). Due to the exceptionally mild conditions, the snow line on the southern side of the Alps was 2200–2500 m, so that the precipitation was not bound as snow, which is atypical of the season. In the central Alps (Upper Piedmont, Ticino) there were no severe floods.

On the north side of the Alps, on the other hand, temperatures were well above 20 ° due to the foehn (mean value in November around Innsbruck  3 °), in Glarus with foehn storms even up to 20 ° at night.

Event frequency

Tropical cyclones of the Rolf type are observed in the Mediterranean every few years, most recently in October 2007 and before that in 1995. In their extreme form, these pseudo-hurricanes, known as medicanes, can regularly form an eye, a cloud-free area in the center of the depth .

In the Genoa area, however, the mudslides as a result of the torrential rain on November 4th were the heaviest since 7/8. October 1970.

consequences

The system brought considerable and persistent heavy rainfalls in Liguria , in Piedmont , on the Côte d'Azur and in the Maritime Alps , as far as the Pyrenees , as well as in Sardinia and Corsica. Particularly in the Turin area , heavy storms with exceptional rain rates at the end of October , in which several people had already died, oversaturated the soil, although the region was then less affected by this event than feared. Persistent gale force winds and gusts of hurricane force created strong surf, which caused damage to the region's coasts.

Italy

The city of Genoa was particularly affected by the falling water of the Fereggiano and the city of Recco on November 4th, when there were extensive traffic obstructions in the area (A 12, roads and railway lines of the Italian and French Riviera), the Tigullio and Piedmont on November 5th ., the province of Savona on the night of 5./6. after heavy thunderstorms. The 6 fatalities were already to be mourned on the 4th in Genoa, where several thousand people had to be evacuated. The inadequate hydrogeological conditions and inadequate security measures in the city also led to political controversy.

France

The French department of Var was also badly affected , where 2,500 people were evacuated from the Argens in particular (the worst damage occurred in the La Palud industrial park near the river in Fréjus ), but also in the Alpes-Maritimes department along the Var river . This region was hit by heavy rains and floods in June 2010, which left 23 people dead. There were floods all over the south of France, from the Pyrénées-Atlantiques department to the Italian border and Corsica .

For France, the state reinsurer Caisse centrale de réassurance  (CCR) estimates the losses incurred as of the 10th of the month at € 550 to 800 million. In addition, the storm has so far claimed five lives, and at least one person who was carried away by the flow of the Var is missing.

Web links

Commons : Ligurian Rainfalls, 2011  - Collection of images, videos and audio files

Individual evidence

  1. ↑ a b c d e f g Tropical storm-like low pressure area over the western Mediterranean. (No longer available online.) In: zamg.ac.at → News. ZAMG , November 9, 2011, archived from the original on November 12, 2011 ; accessed on November 9, 2011 (analysis by the Austrian weather service, with download of the 12-hour satellite image animation, jpeg, 8 or 15 MB). Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / www.zamg.ac.at
  2. ↑ a b Maltempo: Genova sott'acqua, 40 anni di alluvioni mortali. ANSA.it, November 4, 2011, accessed November 4, 2011 (Italian). Alluvione Genova: colpita la stessa zona dell'8 ottobre 1970. meteoweb.eu, November 4, 2011, accessed on November 4, 2011 (Italian). see also Lista di alluvioni e inondazioni in Italia , Italian Wikipedia
  3. ↑ a b Alluvione a Genova / Le vittime sono sei. Più di cento gli sfollati. cittàdigenova.com, November 4, 2011, accessed November 4, 2011 (Italian).
  4. ↑ a b c Agence France Presse (ed.): Crues: fin de l'alerte orange dans le Var, l'heure du bilan dans le Sud . Press release. November 10, 2011 (French, lexpress.fr [accessed November 11, 2011]).
  5. ↑ a b c DWD forecast: November 3, 2011 , 11-04 , 11-05 , 11-06 , 11-07 , 11-08 , 11-09 , 11-10 (all met.fu-berlin.de)
  6. ↑ Tropical storms generally require a water temperature of around at least 26–28 ° in order to develop a self-sustaining weather system, but there are a few exceptions to this in the oceans; In the Mediterranean, the energy supply is overall too low, the eddies are driven by the North African-European-Atlantic compensatory winds
  7. ↑ The high Walli moved to 11 dM from a slump from northwest Deep Quinn I / II southwards pushed across the Black Sea; see DWD forecasts
  8. ↑ a b Position History for 01M
  9. ↑ The British Met Office is formally responsible for the sea weather in the Mediterranean , as it is located in Regional Area VI of the World Meteorological Organization .
  10. ↑ The National Hurricane Center said the system was no name because it is east of the zero meridian developed
  11. ^ Tropical Bulletin , Nov. 7, 1200Z, NOAA
  12. ^ Tropical Bulletin Nov. 7, 1800Z, NOAA
  13. ^ Tropical Bulletin November 8, 0000Z, NOAA
  14. ^ Dvorak Current Intensity Chart , NOAA
  15. ^ Tropical Bulletin , Nov. 8, 1200Z, NOAA
  16. ^ Tropical Bulletin , Nov. 8, 1800Z, NOAA
  17. ^ Tropical Bulletin November 9, 0000Z, NOAA
  18. ↑ cold air drops u. a .: Reports and analyzes on the Mediterranean cut-off supercyclones! Thread. In: Wetterzentrale-Forum. November 4, 2011, accessed November 7, 2011 .
  19. ↑ a b c ROLF brings torrential rain. In: Weather blog. wetter.tv, November 4, 2011, archived from the original on November 7, 2011 ; Retrieved November 9, 2011 .
  20. ↑ Précipitations orageuses intenses sur le Sud de la France. In: Actualités. Meteo France, November 8, 2011, accessed November 9, 2011 (French, synopsis of the French weather service).
  21. ^ Hydrological Bulletin. Federal Office for the Environment FOEN, November 7, 2011, accessed on November 10, 2011 (conclusion of the Swiss Environment Agency).
  22. ↑ Heavy rain in northern Italy - foehn storm in the Alps. In: WetterOnlineTop-Topics. November 4, 2011, accessed November 10, 2011 .
  23. ↑ Thomas Sävert: Eastern Spain October 18, 2007. In: Forces of Nature. Retrieved November 10, 2011 (with satellite image of an even more pronounced eye off the Spanish coast).
  24. ↑ Video images in Sejerlänner: here are some videos from the south of France. Thread reports and analyzes on the Mediterranean cut-off super cyclones! In: Wetterzentrale-Forum. November 8, 2011, accessed November 8, 2011 .
  25. ↑ Six dead in Genoa - storms are raging in northern Italy. In: ›Panorama› World Chronicle. derstandard.at/APA, November 5, 2011, accessed on November 9, 2011 .
  26. ↑ for details see the article Alluvione di Genova del 4 November 2011
  27. ^ Dopo i morti, contestata la Vincenzi. In: Il Secolo XIX. November 5, 2011, archived from the original on February 3, 2012 ; Retrieved November 10, 2011 (Italian).