Medicane

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Tief Qendresa  (I), Nov. 7, 2014 12:10 pm (NASA / GSFC) with brief eye formation; The Scirocco at the front (south-east) and the polar cold air at the rear (north-west) are clearly recognizable, clear of clouds .
January 16, 1995 (NOAA)

A Medicane ( box word for Mediterranean hurricane) is a tropical storm-like storm depression in the Mediterranean region . This form of the Mediterranean Depression probably appears at a frequency of about once a year.

Origin and processes

Medicanes are created especially in autumn when cold air flows from the temperate latitudes towards the equator and a cut-off low is formed in the higher layers of the air (“extra-tropical process”). In the still warm water temperatures of the Mediterranean damp evaporative sea level air mass condenses and forms clouds swirl in the wake of the upper low induced convection . The eye of the vortex systems produced similar to the tropics by the downward movement, with clouds in the resolution while warming deep center. In the vortex, however, wind speeds of a hurricane are rarely reached, but mostly only a storm of up to 120 km / h.

These tropospheric low pressure areas have both extra-tropical and tropical properties.

The main difference between a real tropical hurricane or cyclone and these events is that they do not build up a self-stabilizing or even self-nourishing weather system. In particular, the catchment area in the Mediterranean is too small. The eye-forming eddies are primarily driven from the outside and, in their hurricane-like structure, usually disintegrate into regular low-pressure eddies within hours. Their total lifespan is around two days, well below that of the great eddies of the oceans. Further differences are that the warm core is only pronounced in the lower troposphere , but mostly remains overlaid by the cold altitude core, and that the maximum wind speeds are not reached in the eye, but in the spiral fronts ( occlusions ) as in normal storms . From a bird's eye view (e.g. from a satellite), Medicanes resemble a tropical hurricane and cyclone, but not in terms of their atmospheric-physical processes. Occasionally, similar low pressure areas are formed in the subtropical North Atlantic in the Bermuda , Azores and Canary Islands .

Medicane-like lows often bring heavy rainfall and high winds. In the meantime, a classification based on the mean peak wind speed based on the Saffir-Simpson hurricane wind scale for tropical cyclones has been established:

  • Mediterranean Tropical Depression below 63 km / h
  • Mediterranean Tropical Storm at 64 to 111 km / h
  • Medicane or Mediterranean hurricane from 112 km / h (70  mph , the hurricane scale here is 73 mph, that is> 118 km / h)

Naming and research history

The expression is a trunk word from mediterran [ean] ( 'belonging to the Mediterranean [region] ') and hurricane and was formed in connection with the more precise observation of stormy and rainy weather events in the Mediterranean region. The term originated in the 1980s after satellite images discovered Mediterranean lows with phases of spiral cloud structures and cloud-free zones in the center (the eye) .

Opinions are divided on the question of whether the Mediterranean lows are to be classified as tropical or extra- tropical : they typically mark the boundary of these zones, their southeast flank (front) is driven by hot air masses from the Sahara (the Scirocco ), their western flank (rear) by Atlantic or polar cold air masses. In any case, the direction of pull is controlled by the westerly wind drift , so it goes to the east, not to the west as in the intra-tropical convergence zone .

Overall, the research situation is still unclear, as the data situation is very small due to the late discovery and the rare occurrence. In addition, the richly structured Mediterranean area and the variety of external influences (energy-supplying action centers ) do not lead to such a uniform overall picture as in the formation of the hurricanes over the mid-Atlantic.

The naming of the individual events has not yet been established. The Free University of Berlin , whose names have been used unanimously in Central Europe since 1954, only names those action centers that are weather-effective in Germany. Therefore, only those Mediterranean lows that immigrate from the north into the Mediterranean area are listed, and sometimes Vb lows are named later (and then often outside the actual formation sequence); other Mediterranean lows remain unnamed. The NOAA has temporarily assigned to these events, a number code. There are also names that are given quite arbitrarily by the meteorological organizations of the Mediterranean countries and then distributed by the local media. In  2017 , Numa was called Attila in Italian media , and rarely Zenon in Greece . The provenance of these names remains mostly unknown.

The Medicane Zorbas was formed on September 27, 2018 .

List of Medicanes

A number of Medicanes have been documented and studied over the past few decades; the date on which the storm formed is given:

  • September 23, 1969 (mainly hit Tunisia and Algeria, at least 600 people and several thousand camels perished)
  • January 23, 1982
  • September 27, 1983
  • January 13, 1995 (considered to be the best documented medicane to date)
  • September 12, 1996 (in the western Mediterranean)
  • 4th October 1996
  • October 8, 1996
  • September 25, 2006
  • November 4, 2011 ( Rolf met the Côte d'Azur, Corsica and Liguria)
  • November 7, 2014 ( Qendresa , foehn storm and heavy rain in the Alpine region)
  • October 27, 2016 (90M / Trixi )
  • November 14, 2017 ( Numa / Attila / Zenon , flash floods in Greece)
  • September 27, 2018 ( Zorbas, heavy rain in Greece)

Three studies that appeared in 2007 and 2013 give further examples of Medicanes.

See also

  • Hurricane Vince 2005 - border tropical East Atlantic storm with similar characteristics

Web links

literature

Individual evidence

  1. ↑ a b Medicane DWD: Topic of the day , September 1, 2015. accessed on September 18, 2016.
  2. ↑ Medicane - the cyclone over the Mediterranean In: SRF online, September 17, 2016.
  3. ↑ a b c d Anna Wieczorek: Medicanes - the hurricanes of the Mediterranean? DWD: Topic of the day , September 1, 2015.
  4. ↑ This is why this value can also be found, for example Mediterranean: Severe weather and possible Medicane. Thomas Sävert, in the weather channel Kachelmannwetter , November 14, 2017; the value 112 gives storms in the Mediterranean area - what is a "Medicane"? Fabian ibid., September 7, 2015.
  5. ↑ "medicane TRIXI". In: DWD.de. November 1, 2016, accessed November 17, 2017 .
  6. ↑ In the hot summer of 2018 , a forecast model showed a low pressure vortex that resembled a tropical cyclone on September 18, 2018 at exceptionally high water temperatures . ( Spektrum.de )
  7. ↑ Tropical storms in Europe too? Mediterranean offers a subtropical climate. wetteronline: Weather topics in focus , undated (accessed September 9, 2015) - the other storm discussed there is Cyclone Catarina 2004.