User:Lacunae/23

Mediterranean storms ....cyclogenesis is the process of low-pressure area formation in the Mediterranean Basin. The Mediterranean basin is recognised as one of the main cyclogenetic areas in the world. The seasonal and spatial distribution of these cyclones is variable, largely due to location and morphology.

While the Mediterranean is well known for usually pleasant conditions, the region is frequently affected by sudden events of extreme and adverse weather, which often have high social impacts. The unique geography of the Mediterranean basin, with small and steep river basins which are often highly populated with industrial and tourist areas, makes the Mediterranean especially sensitive to the impact of weather phenomena, especially heavy rain events. Mediterranean cyclones often cause extreme precipitation and strong winds, leading to floods, landslides, storm surges and wind damage.

Cyclone typology of Mediterranean storms
Literature shows that there are three main cyclogenetic regions: the lee of the Atlas Mountains (Sharav cyclones), the lee of the Alps (Genoa cyclones) and over the Aegean Sea. Other cyclogenetic areas include the Iberian Peninsula, the Black Sea and the Middle East. Furthermore, a non-negligible number of cyclones enter the Mediterrannean region from the Atlantic.

Mediterranean tropical-like cyclone
Mediterranean tropical-like cyclones, also sometimes referred to by the portmanteau Medicanes. -a neologism formed from the words Mediterranean and Hurricane introduced in a scientific paper by Businger and Reed (1989).

Although, documented tropical-like cyclones have not usually achieved hurricane intensity, their potential for damage is high due to the densely populated Mediterranean coastal regions.

Two basic facts in addition to its maritime origin reinforce the tropical analogy of a Mediterranean tropical-like cyclone its visual appearance in satellite images and ii) the essential roles of sea-to-air heat fluxes and latent heat release within the core of the storm as revealed by numerical simulations of real events. Observations and simulations agree on the warm-core and small-scale nature of medicanes, which only exceptionally will induce hurricane-force winds (greater than 117km/h) at the surface. Both approaches also demonstrate the great difficulty in formulating a clear-cut distinction between medicanes and the broad spectrum of Mediterranean low-pressure systems, a significant fraction of which appear to be hybrid cyclonic storms that combine in different proportions the physical mechanisms of ordinary extratropical disturbances (e.g. frontal dynamics) with those described above. Some works conclude, for instance, that only 0.5 storms per year fulfill very strict medicane criteria in terms of cloud structure, degree of symmetry, size, and life span on satellite imagery. When these criteria are relaxed to better account for the hybrid types of medicane, 1.5 storms per year are detected according to an informal register of events maintained by (www.uib.es/depart/dfs/meteorologia/METEOROLOGIA/MEDICANES). An independent recent work [Cavicchia, 2013] established that about 1.6 genuine medicanes form over the Mediterranean basin per year.

Indeed, synoptic and numerical analyses of a few well-known cases show that an inevitable precursor of these storms is the approach, or development in-situ, of a deep, cut-off, cold-core cyclone in the upper and middle troposphere.


 * http://www.medicanes.altervista.org/
 * ftp://texmex.mit.edu/pub/emanuel/PAPERS/Romero_Emanuel_2013.pdf
 * http://www.euronews.com/2014/11/10/the-science-behind-the-brutal-beauty-of-mediterranean-cyclones/

On rare occasions, tropical-like systems, that can reach the intensity of hurricanes, occur over the Mediterranean Sea. Such a phenomenon is called a Medicane (mediterranean-hurricane). Although the geographical dimensions of tropical oceans and the Mediterranean Sea are clearly different, the precursor mechanisms of these perturbations, based on the air-sea thermodynamic imbalance, are similar. Their origins are typically non-tropical, and develop over open waters under strong, initially cold-core cyclones, similar to subtropical cyclones or anomalous tropical cyclones in the Atlantic Basin, like Karl (1980), Vince (2005), Grace (2009) or Chris (2012). Sea surface temperatures in late-August and early-September are quite high over the basin (+24/+28°C), though research indicates water temperatures of 20 °C/68 °F are normally required for development.

Meteorological literature document that such systems occurred in September 1947, September 1969, January 1982, September 1983, January 1995, October 1996, September 2006, and November 2011. The 1995 system developed a well-defined eye, and a ship recorded 85 mph (140 km/h) winds, along with an atmospheric pressure of 975 mbar. Although it had the structure of a tropical cyclone, it occurred over 61 °F water temperatures, suggesting it could have been a polar low.

Extratropical cyclones
Main regions of extratropical cyclogensis in the Mediterranean gulf of Genoa (Genoa low) related to the Alpine lee, Southern Italy, Crete and Cyprus.

Extratropical cyclone in Mediterranean subtypes, Tyrhennian low,

Cyclogenesis in the Mediterranean tends to be very localised, two centres, the Gulf of Genoa and Black Sea cyclogenesis through the whole year. Other areas more seasonal, Iberian peninsula summer, Sahara spring and summer, Cyprus spring and summer, Middle east spring and summer, Aegean Sea winter and spring.-http://www.medclivar.eu/schooldocs/lectures/LectureA6A7_Trigo.pdf

whole yearBlack Seawinter & springAegean Seaspring & summerMiddle Eastspring & summerCypruswhole yearGulf of Genoaspring & summerSaharasummerIberian PeninsulaSeason /

med winter cyclones are essentially subsynoptic lows, triggered by the major North Atlantic synoptic systems being affected by local orography and/or low-level baroclinicity over the northern Mediterranean coast.-Trigo 2002

'''spring and summer cyclogenesis events also tend to cluster around a few active regions within the Mediterranean, these are more scattered throughout the whole basin than in winter. The local thermal profiles tend to become dominant toward summer, inducing pronounced diurnal forcings in the life cycles of the lows. The Mediterranean spring may thus be characterized by a wider range of cyclogenesis mechanisms than summer, when thermal forcing seems to prevail. The strong meridional temperature gradient observed along the northern Mediterranean coast during winter shifts down to the southern coast from spring onward. By then, depressions forming over northern Africa often travel eastward along the coastal gradient.'''

'''The geography of the region, namely the high orography skirting the Mediterranean Sea and the existence of embayments and inland seas, determines the relatively small areas where cyclogenesis tends to occur. In the winter this is essentially along the strongly baroclinic northern coast: in the lee of the Alps when an upper trough is blocked by the mountains; over the Aegean and Black Seas when an upper trough moves over the relatively warm water basins.'''

Investigetion of many cases of orographically induced cyclones in the western Mediterranean showed that at least two types of cyclogenesis can be distinguished : the so-called "Ueberstroemungs"-type and "Vorderseiten"-type. The first takes place below a north to northwesterly, the second below a southwesterly upperlevel flow.-http://www.zamg.ac.at/eumetrain/EUMeTrain2006/Cyclone_with_Mistral/intro.htm

Vb Track
Vb track (5b track)

http://www.smhi.se/bloggar/vaderleken-2-3336/de-okanda-5b-lagtrycken-del-2-1.105492 http://www.smhi.se/bloggar/vaderleken-2-3336/de-okanda-5b-lagtrycken-1.105454

Saharan cyclones
Saharan Cyclone (also called the Sharav Cyclones or Khamsin Depression (named after Khamsin wind of North Africa)). The Sharav Cyclone is a spring cyclone. Its tracks lie mainly along the North African coast and turn to the north near the southeastern Mediterranean. in Algeria south of Atlas Mountains and lee side development, and thermal contrast between North Africa and Mediterranean Sea which is coldest in spring, while land is rapidly warming. an annual maximum frequency highest in April and a secondary peak in October. generally move eastward along the southern coast of the Mediterranean. The Sharav Cyclone's track is typically close to the North African coast and in general not over the Mediterranean, as for the marine-type track of the winter cyclones. The Sharav Cyclone has an active warm front, It differs from the winter cyclones, which are characterized by active cold fronts with primarily convective cloud cells. https://twitter.com/NWSOPC/status/718094158393688066 and https://www.facebook.com/NWSOPC/videos/1042186225840108/ https://books.google.co.uk/books?id=X7zA_ZLvDlQC&pg=PA126&lpg=PA126&dq=khamsin+depression&source=bl&ots=QvO5ytA9AA&sig=WNbXGxJH7uYTy8CnMg9ZvrVlyrA&hl=en&sa=X&ei=mWYEVZ_jK4njUa3ugPAP&ved=0CDkQ6AEwAw#v=onepage&q=khamsin%20depression&f=false

Mediterranean Episodes
[] The generic meteorological situations of heavy rains in the Mediterranean regions are of two types: The term " Cévenol " is often misused to describe any episode with torrential rains in the areas of southern France (RAM: as well as cold drop in Spain).

usually autumnal events between September and mid-December.

Mediterranean Monsoon.

Orographic (Cévenol episodes, Épisodes méditerranéen)
Mediterranean Events 10.1175/BAMS-D-15-00088.1 http://sciences.blogs.liberation.fr/home/2014/10/episode-c%C3%A9venol-lexplication-de-m%C3%A9t%C3%A9o-france.html

'''Episodes Mediterranean, The term "Cévenol" is often misused to describe any episode bringing heavy rains to the southern regions of France. While it is true that the Cevennes mountains is known for the intensity of the episodes that affect it (hence the name), strongly rainy situations hit all the Mediterranean arc and are far from being exclusively "Cevenol".'''We might as well talk (but not use) episode "Pyrenean", "Alpine" "corse" or "Provencal" according to the case ... The term "Cevennes episode" is to avoid ... it is better to use the term "Mediterranean-episode". Gota Fria also misused in Spanish media

Cévenol episode in the Cevennes and Languedoc of southern France. http://www.meteofrance.fr/actualites/28475438-dossier-episode-mediterraneen On average three to six times per year, Mediterranean episodes are related to the lifting of hot air, moist and unstable from the Mediterranean which can generate stationary sometimes violent storms. They occur preferentially in autumn, when the sea is warmer, which promotes high evaporation. The term " Cevennes " is often misused to describe any episode bringing torrential rains on southern areas. While it is true that the Cevennes mountain is famous for the intensity of the episodes that affect it (hence the name), strongly rainy situations hit all the Mediterranean arc and thus are far from being exclusively "Cevennes ".-http://www.meteofrance.fr/actualites/28475438-episode-mediterraneen-notre-dossier

late summer early autumn water temperatures in the Mediterranean sea are generally 22-25°C. '''The development of cyclones over the western Mediterranean especially in late autumn is often associated with heavy-rain events in southeastern France and northern Italy. Large scale lifting combined with embedded convection and intensified by the orography of the western Alps and the Apennines may cause flash floods in the narrow mountain valleys due to rainfall of more than 300 mm m-2 per 24 hours. The heavy-rain events are the results of combined advective and convective water vapour transport. The interaction of processes initiating precipitation on different scales causes problems in Quantitative Precipitation Forecast.In the last decade usually at least one cyclone per year caused enormous damage and losses of human lives by floods in that specific area.'''

Rousillon, PACA and Corsica affected generally termed Mediterranean episodes. When flows southeast is organized under the influence of a depression centered in the vicinity of the Balearic or the Atlantic, off the Iberian peninsula, warm and unstable air is advected from the Mediterranean to Languedoc and the Cevennes. air mass is lifted and undergoes a strong cooling and a significant condensation. This results in the formation of clouds with strong vertical development called cumulonimbus. These storm clouds will dump heavy rainfall in the foothills of the Cevennes; as wet food came from Mediterranean persists, heavy rains pour over the same areas where overlapping of extreme rain (sometimes more than 500 liters / m2) that can be met with respect to such episodes. We talk as orographic blocking the mountain barrier Cevennes form a real barrier against wet and unstable air masses.

DANA- Depresión Aislada en Niveles Altos(Isolated depression at high altitude) -Gota fria
Gota Fria (Cold drop) is an archaic meteorological term, used popularly in Spain, which has commonly come to refer to any high impact rainfall events occurring in the Autumn along the Spanish Mediterranean coast. Gota Fria (Cold Drop) used as a synonym for heavy rain particularly in the autumn which causes societal problems. concept developed from the German meteorologists in the 19th century, and persisted in meteorological parlance into the post

superseded by the concept of the cutoff low, though they are not identical terms, as the spanish Gota Fria has been somewhat generici to refer to high impact rains usually in the autumn season.

Modern Spanish meteorological parlance DANA- Depresión Aislada en Niveles Altos (Isolated depression at high altitude), for cut off low seperated from jet stream circulation, explicit use of high level/altitude to differentiate from thermal lows on the Iberian peninsula.

We are aware that "the cold drop" is part of the popular terminology, hardly expendable from colloquial language.

It is not the dana (nor the cold drop) that generates such sudden and torrential rainfall. The dana only establishes the favorable environment for organized storms to develop and maintain: convective trains, SCM, CCM and other structures. There are DANAs that do not generate even cloudiness, and others that are dangerous. There are episodes of torrential rains in the Mediterranean associated with Cold Drops, and others that have nothing to do with it. In order for a Cold Drop to be able to generate storms and cloudiness capable of producing torrential rains, the participation of many other ingredients is necessary, most of which are found in low layers: high humidity, strong temperature gradient in middle layers. low, energy that is capable of generating ascents of the adjacent air masses and thus convection, convergence in low layers ...

'''The main mechanism generating these heavy precipitation events (HPEs) is the strong instability induced by the warm and moist air that for most of the year sits over the mild Mediterranean waters, along with the presence of a low pressure system (usually produced by a Mediterranean cyclogenesis event) that can trigger convection and organize the flow (Llasat, 2009). Other factors such as the complex orography of the region, often take also a very important role (e.g. Buzzi et al., 1998; Rotunno and Ferretti, 2003). Most cases occur in autumn, when the combination of a still warm sea surface temperature (after a peak in late summer), and a southward displacement of the jet stream (which usually favors the appearance of Atlantic lows or cut-off-lows affecting the 5 WMR), make this season the most favourable for the development of these extreme events (Llasat et al., 2013)'''

Stationary cells
'''These storm systems do not cover very large areas, but generate very intense rainfall intensities (often greater than 100 mm / h). Sometimes they can be regenerated (called stationary cells) by creating a large surface of a cold air bubble, which then acts as a mechanism for raising the mass of air that reaches the same place.For example, such an episode was observed on September 22, 1993 in Aix-en-Provence, on September 6, 2010 in Cavaillon, December 1, 2003 in Marseille, on September 29, 2014 and August 23, 2015, in Montpellier.'''
 * http://www.meteofrance.fr/actualites/28887359-deux-episodes-mediterraneens-successifs
 * http://www.smhi.se/bloggar/vaderleken-2-3336/kraftiga-hostregn-over-cevennerna-1.97520
 * https://actu.lachainemeteo.com/actualite-meteo/2017-10-19/episodes-cevenols-:-le-dossier-45202

Examples

 * 1957 Valencia flood
 * Aude_(river)
 * 2010_Var_floods
 * Autumn 2014
 * October 2015 (fr:Inondations_d%27octobre_2015_dans_les_Alpes-Maritimes)
 * http://www.meteofrance.fr/prevoir-le-temps/phenomenes-meteo/les-pluies-intenses#

Roles in major flooding events
A relatively warm body of water, net overall evaporation surrounded by high topography of the Alps, Apennines, Balkans, Anatolian mts, Atlas mts..


 * 2013 Sardinia floods
 * 2014 Southeast Europe floods
 * 2014 Bulgarian floods

other

 * Euroclydon
 * 8 principal winds of the Mediterranean, Tramontane Gregale Levant Sirocco Ostro Libeccio Ponente Mistral

Black Sea cyclogenesis
Storm in the Black Sea led to the founding of modern meteorology. during the Crimean War a storm on 14 November 1854 loss of 38 merchant ships and 400 sailors died. The French minister of war, Urbain Le Verrier *asked ?* to investigate the cause of the disaster. A storm across the north and west of Europe on the 12 November, established a network of weatehr observation stations connected by electric telegraph began in 1863 Paris Observatory warning telegrams of weather and produce daily weather maps from information collected.

2012 Krasnodar Krai floods

Store
'''The Mediterranean region (MR) is one of the most active regions of the Northern Hemisphere in terms of cyclone activity, displaying a distinct regional maximum of cyclone numbers (e.g. Trigo et al., 1999; Ulbrich et al., 2009). The MR favours a wide variety of cyclogenesis mechanisms, such as the deepening of mid-latitude perturbations at the lee of the Pyrenees or the Alps, their fuelling by low-level moisture sources and/or by low-level baroclinicity along the coast, or the formation of thermal lows over warm inland regions (e.g. McGinley, 1982; Radinovic, 1986; Michaelides et al., 1999). As a consequence, the MR is prone to the occurrence of cyclones with a broad range of characteristics, from synoptic to mesoscale, and a variety of intensities and depths (see Lionello et al., 2006, and Ulbrich et al., 2012, for a general description).'''

there are two preferred regions for cyclogenesis: Cyprus area and the gulf of Genoa.typically lee baroclinic disturbances.

'''The Mediterranean area also presents the highest concentration of real cyclogenesis in the world, at least during winter. Some of the Mediterranean cyclogeneses are so active as to be considered even as "meteorological bombs". Mediterranean real cyclogenesis shows a very high concentration in the Gulf of Genoa region. Nevertheless, there are other areas with quite frequent true cyclogenesis. Secondary maxima are located in the Cyprus and Aegean region and other relative maxima are situated in the Adriatic, in the Palos-Algerian sea or in the Catalonian-Balearic sea and gulf of Lyon.'''

changes in the cyclonic routes from month to month may be found in the changing land-sea contrast in association with the complex topography of the region. '''The Mediterranean basin is surrounded by complex orography, with high mountain ranges such as the Atlas or the Alps. Besides, the Mediterranean Sea is an almost enclosed basin, which acts as a reservoir of heat and moisture, with a remarkable land–sea contrast.'''

'''The factors determining the relation-ship between the MC track and the Atlantic storm-track have been studied using climate model simulations (e.g.Brayshaw et al., 2010). These studies found that width of the Hadley cell, mid-tropospheric baroclinicity and Mediterranean sea surface temperature are the main climatic factors affecting the Mediterranean storm-track population and intensity'''.

western and eastern Mediterranean basins.''' The relatively small annualcycle over the whole basin reflects the completely dif-ferent seasonalities in the separate cyclogenetic regions.For example, there is a peak of activity in spring overthe Sahara, in summer over Iberia, and a smoother an-nual cycle  over  the  Black  Sea. The western  Mediterranean  has  a  much  more  marked  seasonality  than  the eastern  basin.'''

An example is over theGulf of Genoa where, although cyclones are a constantfeature over the whole year, they are generally deeper,and have more severe weather in winter than during thesummer, when they are, in fact, more frequent. development of  Mediterraneanlows becomes progressively more dependent on the timeof day throughout spring and summer. This is a featurethat clearly  separates  winter  from  spring/summer  cy-clogenesis processes.

The importance of [cut-off lows in major flooding.