 | This article needs additional citations for verification .(August 2013) |
A Genoa low (also known as Genoa cyclogenesis, Ligurian depression, or V(5)-track cyclone) is a cyclone that forms or intensifies from a pre-existing cyclone to the south of the Alps over the Gulf of Genoa, Ligurian Sea, Po Valley and northern Adriatic. [1] Vb cyclones are rare events which occur on average only 2.3 times per year. [2]
The northwestern Mediterranean and the Gulf of Genoa in particular, are not only a transition area for passing cyclones, but are frequently areas of cyclogenesis. [3] [4] Low pressure areas move into or are formed as a result of North Atlantic air entering the Mediterranean Sea between the Alps and the Massif Central, via the Rhone Valley, or via the Carcassonne gap between the Pyrenees and Massif Central. This cold and moist air enters the Mediterranean basin, and is deflected by the high mountains of northwest Corsica, which divert the air mass to the northeast, triggering cool and wet Libeccio winds in response into the Ligurian Sea, which in turn hit the western Apennines located in the immediate vicinity of the sea.
Several factors that have special relevance in the development of depressions south of the Alps are:
A complex interaction is established between the orography of Liguria and the contrast between the cold and humid air mass and the warmer water of the Ligurian Sea, the process ends with the formation of a low pressure area over the Ligurian Sea, just near the city of Genoa. Genoa low cyclogenesis can occur at any time of year, though usually situated further south during the summer. [1] Cyclogenesis is shifted to the east depending on the amount of cold air entering the Po Valley, and generally shifts to the Gulf of Venice when little enters the valley. [1]
The depressions bear rain, often intense, on the Ligurian coast and hills of Tuscany, due to orographic lift which affects the southern side of the Apennines. The area of low pressure is slow moving, and may follow a trajectory from west to east, then going on to affect the regions of the Adriatic, or move from the north-west to south-east down along the Tyrrhenian Sea: in this last case, the structure will reach the same cyclonic area of formation of Tyrrhenian depressions, although not related to the latter.
Most Genoa lows remain stationary or leave a residual trough to the south of the Alps. [1] Three principal tracks which they typically follow were identified by Wilhelm Jakob van Bebber who classified European windstorm tracks ("Zyklonenbahnen" in German) in 1891. [3] To this date, track V of the latter group has remained in common use, unlike the large majority of van Bebber's tracks. [3] The V track is linked to flooding events in central and eastern Europe, low pressure areas (south of the Alps) can track across France into the Mediterranean Sea where they pick up additional moisture, or form, and then move into central and eastern or southern Europe. [5] the tracks diverge from the Genoa low formation area along the following pathways.
A strong southwesterly flow in the upper atmosphere leads the lows to the northeast and north-northeast, ("Zugstrasse Vb" Van Bebber) towards the Vienna Basin. The lows then glide over colder and denser air from the northwest and are lifted orographically by the Bohemian Massif, Ore Mountains, Sudetes, Beskids and Tatra Mountains. [6] The warm and moist air masses cause prolonged and abundant precipitation during slow Meridional flow over the upper catchments of both the southern and northern European Watershed. Flooding then progresses down their major rivers of central Europe. [7] This 'Vb-track' displays a high potential for large summer floods in Europe. [8] Although the link between large summer floods and the Vb track have also been described as having a significant but weak correlation. [6]
Examples of flooding events which follow this pattern are:
Due to the expected warming of the future climate it is predicted that the annuality of Vb-cyclones will decrease. The decrease in Vb-cyclones could be caused by the shift of the cyclone track over Europe to the north. Modelling has shown that precipitation from future Vb-cyclones will have a greater impact on the eastern coasts of the Mediterranean Sea and a lesser impact on the Alpine region compared to the precipitation pattern of current Vb-cyclones. [13]
The Vc track draws the lows across the Panonian plain towards the Carpathian Mountains and on towards western Ukraine and Moldova.
If there is a strong anticyclone over the Balkans, Turkey and the Black Sea, the usual track of the low is southeasterly, skirting the northern coast of the Mediterranean Sea. It is this track that moves the low across the Tyrrhenian Sea. Even after the primary low has moved out of the Tyrrhenian Sea-central Mediterranean area, if a residual trough remains south of the Alps, as is often the case, new centers can develop and occasionally move southeastward along the west coast of Italy. [1] It is also common that a Genoa Low that has moved to the southwest will stall and become stationary, just to the west of the foot of the Italian boot, and this often will be associated with new low centers developing to the east over the Ionian Sea. [1] In this case, gale force Bora are typically generated by the time the depression moves into the Ionian Sea. [14]
The geography of Italy includes the description of all the physical geographical elements of Italy. Italy, whose territory largely coincides with the homonymous geographical region, is located in southern Europe and comprises the long, boot-shaped Italian Peninsula crossed by the Apennines, the southern side of Alps, the large plain of the Po Valley and some islands including Sicily and Sardinia. Italy is part of the Northern Hemisphere. Two of the Pelagie Islands are located on the African continent.
In meteorology, a cyclone is a large air mass that rotates around a strong center of low atmospheric pressure, counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere as viewed from above. Cyclones are characterized by inward-spiraling winds that rotate about a zone of low pressure. The largest low-pressure systems are polar vortices and extratropical cyclones of the largest scale. Warm-core cyclones such as tropical cyclones and subtropical cyclones also lie within the synoptic scale. Mesocyclones, tornadoes, and dust devils lie within smaller mesoscale. Upper level cyclones can exist without the presence of a surface low, and can pinch off from the base of the tropical upper tropospheric trough during the summer months in the Northern Hemisphere. Cyclones have also been seen on extraterrestrial planets, such as Mars, Jupiter, and Neptune. Cyclogenesis is the process of cyclone formation and intensification. Extratropical cyclones begin as waves in large regions of enhanced mid-latitude temperature contrasts called baroclinic zones. These zones contract and form weather fronts as the cyclonic circulation closes and intensifies. Later in their life cycle, extratropical cyclones occlude as cold air masses undercut the warmer air and become cold core systems. A cyclone's track is guided over the course of its 2 to 6 day life cycle by the steering flow of the subtropical jet stream.
Liguria is a region of north-western Italy; its capital is Genoa. Its territory is crossed by the Alps and the Apennines mountain range and is roughly coextensive with the former territory of the Republic of Genoa. Liguria is bordered by France to the west, Piedmont to the north, and Emilia-Romagna and Tuscany to the east. It rests on the Ligurian Sea, and has a population of 1,557,533. The region is part of the Alps–Mediterranean Euroregion.
The Apennines or Apennine Mountains are a mountain range consisting of parallel smaller chains extending c. 1,200 km (750 mi) along the length of peninsular Italy. In the northwest they join with the Ligurian Alps at Altare. In the southwest they end at Reggio di Calabria, the coastal city at the tip of the peninsula. Since 2000 the Environment Ministry of Italy, following the recommendations of the Apennines Park of Europe Project, has been defining the Apennines System to include the mountains of north Sicily, for a total distance of 1,500 kilometres (930 mi). The system forms an arc enclosing the east side of the Ligurian and Tyrrhenian Seas.
The 2000 Atlantic hurricane season was a fairly active hurricane season, but featured the latest first named storm in a hurricane season since 1992. The hurricane season officially began on June 1, and ended on November 30. It was slightly above average due to a La Niña weather pattern although most of the storms were weak. It was also the only Season to Include 2 storms in Ireland. The first cyclone, Tropical Depression One, developed in the southern Gulf of Mexico on June 7 and dissipated after an uneventful duration. However, it would be almost two months before the first named storm, Alberto, formed near Cape Verde; Alberto also dissipated with no effects on land. Several other tropical cyclones—Tropical Depression Two, Tropical Depression Four, Chris, Ernesto, Nadine, and an unnamed subtropical storm—did not impact land. Five additional storms—Tropical Depression Nine, Florence, Isaac, Joyce, and Leslie—minimally affected land areas.
The 1977 Atlantic hurricane season was a very inactive Atlantic hurricane season, with only six tropical storms. The season officially began on Wednesday, June 1, 1977 and lasted until Wednesday, November 30, 1977. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin. The first tropical depression of the season developed over the western Caribbean Sea on June 13, 12 days after the start of the season, with three other tropical depressions following suit in July and early August. Then, on August 29, Hurricane Anita formed and rapidly intensified to a Category 5 hurricane on September 1, before weakening slightly and striking Mexico as a high-end Category 4 hurricane on the Saffir–Simpson hurricane wind scale, bringing strong winds and heavy rainfall. At least 25,000 people were left homeless and 11 fatalities were reported, with total damages still yet to be known to date.
Tramontane is a classical name for a northern wind. The exact form of the name and precise direction varies from country to country. The word came to English from Italian tramontana, which developed from Latin trānsmontānus, "beyond/across the mountains", referring to the Alps in the North of Italy. The word has other non-wind-related senses: it can refer to anything that comes from, or anyone who lives on, the other side of mountains, or even more generally, anything seen as foreign, strange, or even barbarous.
The 2005 North Indian Ocean cyclone season caused much devastation and many deaths in Southern India despite the storms’ weakness. The basin covers the Indian Ocean north of the equator as well as inland areas, sub-divided by the Arabian Sea and the Bay of Bengal. Although the season began early with two systems in January, the bulk of activity was confined from September to December. The official India Meteorological Department tracked 12 depressions in the basin, and the unofficial Joint Typhoon Warning Center (JTWC) monitored two additional storms. Three systems intensified into a cyclonic storm, which have sustained winds of at least 63 km/h (39 mph), at which point the IMD named them.
Tropical cyclogenesis is the development and strengthening of a tropical cyclone in the atmosphere. The mechanisms through which tropical cyclogenesis occurs are distinctly different from those through which temperate cyclogenesis occurs. Tropical cyclogenesis involves the development of a warm-core cyclone, due to significant convection in a favorable atmospheric environment.
A western disturbance is an extratropical storm originating in the Mediterranean region that brings sudden winter rain to the northern parts of the Indian subcontinent, which extends as east as up to northern parts of Bangladesh and South eastern Nepal. It is a non-monsoonal precipitation pattern driven by the westerlies. The moisture in these storms usually originates over the Mediterranean Sea, the Caspian Sea and the Black Sea. Extratropical storms are a global phenomena with moisture usually carried in the upper atmosphere, unlike their tropical counterparts where the moisture is carried in the lower atmosphere. In the case of the Indian subcontinent, moisture is sometimes shed as rain when the storm system encounters the Himalayas. Western disturbances are more frequent and stronger in the winter season.
The 2001–02 South Pacific cyclone season was a below-average year in which only five named storms formed or entered the South Pacific basin. It began on November 1, 2001 and ended on April 30, 2002. These dates conventionally delimit the period of each year when most tropical cyclones form in the southern Pacific Ocean east of 160°E. Additionally, the regional tropical cyclone operational plan defines a tropical cyclone year separately from a tropical cyclone season, and the "tropical cyclone year" runs from July 1, 2001 to June 30, 2002. The season's sixteen tropical depressions existed within these dates with the first developing on November 29 and the last dissipating on April 22.
The 2004 North Indian Ocean cyclone season was the first in which tropical cyclones were officially named in the basin. Cyclone Onil, which struck Pakistan, was named in late September. The final storm, Cyclone Agni, was also named, and crossed into the southern hemisphere shortly before dissipation. This storm became notable during its origins and became one of the storms closest to the equator. The season was fairly active, with ten depressions forming from May to November. The India Meteorological Department designated four of these as cyclonic storms, which have maximum sustained winds of at least 65 km/h (40 mph) averaged over three minutes. The Joint Typhoon Warning Center also issued warnings for five of the storms on an unofficial basis.
The 2002 North Indian Ocean cyclone season was a below average season in terms of tropical cyclone formation. The season had no official bounds, but most storms formed in either May or after October. No depressions or storms formed during the monsoon season from July to September, the first such instance on record. There are two main seas in the North Indian Ocean – the Bay of Bengal to the east of the Indian subcontinent – and the Arabian Sea to the west of India. The official Regional Specialized Meteorological Centre in this basin is the India Meteorological Department (IMD), while the Joint Typhoon Warning Center (JTWC) releases unofficial advisories. An average of four to six storms form in the North Indian Ocean every season with peaks in May and November. Cyclones occurring between the meridians 45°E and 100°E are included in the season by the IMD.
The 2000 North Indian Ocean cyclone season was fairly quiet compared to its predecessor, with all of the activity originating in the Bay of Bengal. The basin comprises the Indian Ocean north of the equator, with warnings issued by the India Meteorological Department (IMD) in New Delhi. There were six depressions throughout the year, of which five intensified into cyclonic storms – tropical cyclones with winds of 65 mph (105 km/h) sustained over 3 minutes. Two of the storms strengthened into a Very Severe Cyclonic Storm, which has winds of at least 120 km/h (75 mph), equivalent to a minimal hurricane. The Joint Typhoon Warning Center (JTWC) also tracked storms in the basin on an unofficial basis, estimating winds sustained over 1 minute.
Hybrid low may refer to a number of different meteorological depressions:
Mediterranean tropical-like cyclones, often referred to as medicanes but sometimes also as Mediterranean cyclones or as Mediterranean hurricanes, are meteorological phenomena occasionally observed over the Mediterranean Sea. On a few rare occasions, some storms have been observed reaching the strength of a Category 1 hurricane, on the Saffir–Simpson scale, and one storm has been recorded reaching Category 2 intensity. The main societal hazard posed by medicanes is not usually from destructive winds, but through life-threatening torrential rains and flash floods.
Cyclone Sam(JTWC designation: 03S) was an intense tropical cyclone that brought flooding rainfall to a wide swath of northern Australia in December 2000. The first tropical cyclone of the regional season, Sam originated from a tropical low that formed in the Arafura Sea on 28 November. Tracking generally westward, the initial low-pressure area remained generally weak until it entered the Timor Sea, by which time it had strengthened into a tropical cyclone on 5 December. Though a subtropical ridge was forcing the cyclone westward at the time, an approaching shortwave trough caused Sam to track southward the following day, towards the Australian coast. During its southward progression, Sam rapidly intensified, and reached its peak intensity on 8 December. Soon afterwards, the storm made landfall near Lagrange, Western Australia at the same intensity. Once inland, Sam was slow to weaken as it re-curved eastward, and persisted for nearly a week inland before dissipating on 14 December.
Tropical Storm Rolf, also known as Tropical Storm 01M, was an unusual Mediterranean tropical storm that brought flooding to Italy, France, Spain, and Switzerland in November 2011. Rolf originated from an extratropical system near western France on 4 November. Despite the generally unfavorable conditions in the Mediterranean Sea, Rolf transitioned into a subtropical depression on 7 November, before becoming a tropical storm later that day. On 8 November, Rolf reached its peak intensity, with 1-minute sustained winds peaking at 85 km/h (53 mph) and a minimum central pressure of 991 mb (29.3 inHg). During the next day, the storm made landfall on the island of Île du Levant, in France, and soon afterward, near Hyères in southeastern France. Following its second landfall, Rolf quickly weakened and dissipated on 10 November. Rolf was the first tropical cyclone ever to be officially monitored by the NOAA in the Mediterranean Sea.
The 2018 North Indian Ocean cyclone season was one of the most active North Indian Ocean cyclone seasons since 1992, with the formation of fourteen depressions and seven cyclones. The North Indian Ocean cyclone season has no official bounds, but cyclones tend to form between April and December, with the two peaks in May and November. These dates conventionally delimit the period of each year when most tropical cyclones form in the northern Indian Ocean.
Cyclone Julia brought heavy flooding and hurricane conditions to parts of Europe, the Mediterranean region, and North Africa in February 2012. The second tropical or subtropical cyclone, second named storm, and the strongest storm of the 2011–12 Mediterranean hurricane season, Julia originated from an extratropical system that split off from its parent storm, in the western Mediterranean Sea on February 2. Despite the unfavorable conditions in the Mediterranean Sea, Julia strengthened into a powerful subtropical cyclone, with winds peaking at 61 mph (98 km/h), and a minimum pressure of 982 mbar (29.0 inHg) on February 6. On February 7, the storm made landfall on the Peloponnesian Peninsula, and eventually dissipated over Turkey. Cyclone Julia caused at least $6.4 million in damages, and resulted in at least 12 deaths. The storm also worsened the effects of the Early 2012 European cold wave across Europe and North Africa.
