Supercell

A WORLD OF WIND These are some (hopefully most) of the worlds winds: Abroholos - A violent squall, paticularly prevalent in summer, that occurs off the south-eastern coast of Brazil. Andhi - A violent squall or dust storm occuring in late spring in north-western India. Barat - A squally west or north-west wind that occurs between December and February on the northern coast of the Phioippine island of Celebes. Berg Wind - A hot, dry fohn wind originating over the South African Plateau. It is particularly common during the winter season, and especially affects the western coastal region. Bise - A cold north or north-easterly wind, blowing from the mountains, that affects western Switzerland and eastern France. Although normally relatively dry, in winter it may bring heavy snow or hail. Bora - A cold, dry downslope wind (often violent with squalls) that affects the Dalmation coast when there is low pressure over the Mediterranean and high pressure over central Europe and the Balkans. Strongest in winter, it may be accompanied heavy cloud, rain or snow when a depression lies over the Adriatic. The term is sometimes applied to similar fall winds in other parts of the world. Brickfielder - A strong, hot, dry, and dusty wind in southern Australia(paricularly in New South Wales) which precedes the passage of a depression. Buran - A strong north-easterly wind in Siberia and Central Asia,particularly in the extreme blizzardconditions that occur in winter. Over the tundra which is also known as purga Burga - A severe north-easterly wind in Alaska that brings snow or ice pellets. Chinook - A strong, warm and exceptionally dry fohn wind that descends the eastern slope of the rockies , and may bring an abrupt temperature rise, the disappearance of lying snow, and a risk of desiccation and consequent fire hazard. Often heralded by a line of low cloud (the chinook arch) parallel to the Rockies. A chinook was responsible for the most rapid temperature rise ever recorded: 27C in 2 minutesat Spearfish, South Dakot, on 23 January 1943. The term is occasionally applied to a warm, moist wind from the sea that affects the coasts of Washington and Oregon. Cierzo - A dry, cold, north-westerly wind that flows down the Ebro Valley in Spain during the winter months. Doctor - A name used in various parts of the world for a wind that is invigorating or brings relief from uncomfortably hot (or hot and humid) conditions. Specifically applied to the harmattan on the Guinea coast of north-wast Africa, various sea-breezes (especially the very strong Cape Doctor around Cape Town in South Africa), and to certain fall winds, as in Jamaica. Etesian Winds - Generallynortherly winds (between north-west and north-east) that blow in the summer season (between May and September) over the Aegean Sea and eastern Mediterranean. They are known as meltemi in Turkey. Fall Wind -A strong downslope wind that remains cold, despite adiabatic heating 9and thus differs from a fohn). It is a katabatic wind that has its origins in a pool of cold air over high ground. The most extreme examples are the violent winds that sweep down from the Antarctic ice sheet,reaching a record of around 320 km/h, and which may maintain hurricane-force winds for days or weeks on end. Fall winds are largely responsible for the annual mean wind speed of 67 km/h recorded at Cape Dennison, Commonwealth Bay, Antarctica. Fohn (foehn) - A warm and often extremely dry wind that descends in the lee of a mountain barrier, Fohn winds occur under stable conditions that are conducive to the formation of large-amplitude lee waves. Air from very high levels (well above mountain-tops) may be brought down to the surface and undergo considerable adiabatic heating. Fohn winds 9such as the chinook) are noted for there rapid temperature rise, their desiccating effect, and rapif disappearance of snow cover. Although originally applied to winds in the Alpine region, the term is now used for all similar winds. Galera - A cold north-westerly wind that affects the narrow coastal strip north of the Cantabrian Mountains, inSpain, and which is paricularly frequent in winter. Ghibli - A hot, dry and dusty southerly wind that occurs in Libya in spring and early summer. A local name for the sirocco , and known as the khamsin farther east in Egypt. Greco - A north-east wind over the Golfe du Lion in the western Mediterranean. Gregale - A strong north-east wind over the western and central Mediterranean, most frequent in Winter.It occurs when there is high pressure over Central Europe and low pressure over North Africa. Haboob - 1. A severe dust storm or sandstorm in northern and central Sudan which transports and deposits large quantities of material. Haboobs are strongest in April and May, but occur in every month except November. The wind direction may be north (in winter) or east, south-east, or south (in summer). The storm front is extremely dense and turbulent and may be up to 1000 m high. 2. A local Canadian term for a prairie dust stom. Harmattan - A dry, dust-laden, but relatively cool north-easterly or easterly wind in north-west Africa, part of the trade-wind system. In the wet (summer) season it tends to give way to monsoon winds from the gulf of Guinea and the Atlantic Ocean. Helm wind - A strong, blustery wind that descends the western side of the Cross Fell range in Cumbria. It is a lee wave produced by a prevailing north-easterly flow and exhibits a fohn effect. A bank of cloud, the helm, lies along the mountain-tops or just above them. At times, a further narrow, stationary, but rotating roll cloud forms roughly parallel to the first and a few kilometres downwind. The helm bar is a rotor cloud and the surface wind dies away beneath it. Farther away from the fells there may be a gentle westerly flow towards the mountains. Katabatic Wind - A wind consisting of dense air that has cooled by radiative cooling over upland areas or contact with snow and ice fields and which then drains down into the valleys. Also known as a drainage wind and a mountain breeze. Examples of strong katabatic winds are the bora, mistral and the extreme winds that drain fom the antarctic ice cap. Khamsin - A hot, dry dusty wind occuring in ;ate spring and summer around the eastern Mediterranean. A counterpart of the sirocco, it is a southerly wind over Egypt , and an easterly wind over the Negev Desert and parts of Saudi Arabia. Like the sirocco, it is drawn northwards or westwards ahead of an approaching depression. Kona storm - A severe south-westerly wind in the Hawaiian Islands which is associated with the passage of a secondar depression to the north. It brings heavy rain to the dry, south-western side of the islands normally in the lee of the prevailing north-easterly trade winds. Kosava - A ravine wind in the valley of the Dunabe, where it cuts through the Carpathian Mountains to the east of Belgrade. Leste - A hot, dry, dusty easterly or south-easterly wind from Morocco that reaches the Canary Islands and Madiera. It is closely related to the sirocco. Levanter - A humid easterly wind that affects the Straits of Gibraltar and the eastern coasts of Spain, most frequent in summer and early autumn. It generally occurs in stable air under an inversion and may produce a banner cloud behind the Rock of Gibraltar. Leveche - A hot, dry wind on the narrow coastal strip of south-eastern Spain. It brings dusty continental tropical air from the Sahara, and is particularly frequent in summer. Sometimes known as the lebeche. Libeccio - The local name for a blustery south-westerly or westerly wind that occurs over Corsica and the Central Mediterranean. It is particularly strong in winter, and may bring heavy rain or thunderstorms in summer. Maestro - A north-westerly wind that occurs in summer over the western part of the Adriatic. The name is also given to a similar wind on the coast of Corsica and Sardinia. Meltemi - The Turkish name for the estian winds. Mistral - A strong, cold, dry and squally northerly wind that blows down the Rhone valley in south-eastern France and extends some way into the Golfe du Lion in the Mediterranean. It may be a purely katabatic wind, but also arises when a low-pressure centre lies over the Ligurian or Tyrrenian Seas. Its strength is increased by the funnelling effect of the Rhone valley. It is most violent in winter and spring, and may reach 130 km/h over the Rhone delta. Nor'easter - A strong or gale-force north-easterly, particularly the cyclonic storms that affect the northern portion of the East Coast of the United States during the winter and which bring the greatest snowfalls. Norther - A cold, northerly wind that often brings a drastic drop in temperature, especially the wind exprienced over the southern region of the Great Plains in North America. Such a sudden outbreak of polar air often crosses the Gulf of Mexico and reaches Central America, where it is known as the norte. Pampero - A severe line squall that occurs over the pampas of Argentina and Uruguay. It is followed by by a cold, blustery, southerly or south-westerly wind and often brings heavy rain and thunderstorms, together with a considerable drop in temperature. Ponete - A westerly wind along the coasts of the north-western Mediterranean. It tends to be a land-breeze around the Golfe du Lion, and a weakened flow from the mistral on the Cote d'Azur and over the Ligurian Sea, where it often precedes the tramontana. Poniente - A westerly wind in the straits of Gibraltar. Santa Ana - A hot, dry easterly wind that affects Los Angeles region of southern California, named after the valley through which the main flow occurs, and which acts to intensify it as a mountain-gap wind. The wind originates over the dry interior plateau, and its temperatur and desiccating effects are increased by adiabatic heating during its decent, as with a fohn wind. Seistan - A strong north-westerly wind over eastern Iran and Afganistan. It is associated with the summer monsoon low-pressure region over north-western India and begins in late May or early June, blowing almost continually until the end of September. It transports considerable quantities of sand and dust, which it deposits as large dunes. Shamal - A hot, dry north-westerly wind that occurs over Iraq and the region of the Persian Gulf. It is particularly strong and persistant during the daytime in summer, but tends to weaken at night. Like the seistan, it is associated with the summer monsoon low over northern India. Simoom - A hot, dry wind or whirlwind that occurs, particularly in summer, in North Africa and Arabia. It often carries large quantities of suffocating sand and dust, but normally persists for just 10-20 minutes. Sirocco - A warm, dustladen, southerly wind in the mediterranean region. Variously known as the ghibli in Libya, khasmin in Egypt, and the south-easterly leveche in Spain. It is paricularly prevalent in spring and autumn and is normally drawn northwards ahead of the cold front of a depression. With a long fetch across the Mediterranean it may becom very humid and produce extensive stratus cloud. Solano - An easterly or south-easterly wind on the south-eastern coast of Apain, generally hot and humid, but which may be hot, dry, and dust laden. It normally originates as a sirocco. Squamish - A strong, often violent north-easterly or easterly wind that blows through certain fjords in British Columbia. It is a katabatic wind, whose strength is increased by the funneling effect of the fjords' sides. Tehuantepecer - A violent, squally, northerly or north-easterly wind in the Gulf of Tehuantepec on the Pacific Coast of southern Mexico and crosses isthmus in the gap between the Sierra Mdre del Sur and the Guatemalen mountains. Tornado - A form of thundery squall encountered in West Africa, particularly around the Gulf of Guinea. It often occurs as a line squall, and is especially frequent at the beginning and end of the rainy season. Tramontana - A northerly or north-easterly wind over north-eastern Spain, south-eastern France, the Balearic Islands, the western Mediterranean, and Italy, which is normally cold and dry. Also French tramontane. Vendavales - A strong, blustery south-west wind in the Strait of Gibraltar and on the southern and south-eastern coasts of Spain. It occurs with depressions from late autumn to early spring, and is often accompanied by violent squalls and thunder. Veranillo - On the Pacific coast of Central America and Mexico. Verano - "see Veranillo" Verano is a longer lasting than th Veranillo. Williwaw - A sudden gust of wind thar descends from mountains borderin the sea; the term is particularly applied to conditions in the Strait of Magellan and also the Aleutian Islands. Zonda - A warm wind in Argentina, either a wintertime westerly fohn wind that descends the eastern slopes of the Andes, or a moist northerly ahead of a depression. Beaufort Scale Beaufort, Rear-Admiral Sir Francis (Born - Navan, Ireland, 1774. Died Greenwich, 17 December 1857). British naval officer and hydrographer, who in 1806, as Commander, published a method of measuring the wind at sea, initially based on the effects upon a frigate (such as the specific sails that could be carried). The Beaufort scale was eventually adopted by the Royal Navy in 1838. Beaufort became head of the Admiralty's Hydrographic Office in 1829, and transformed the office into the world's foremost hydrographic organization. Force 0 - Calm. Smoke rises vertically. <1km/h Force 1 - Light air. Direction of wind shown by smoke but not by a wind vane. 1-5km/h Force 2 - Light Breeze. Wind felt on face, leaves rustle, wind vane turns to wind. 6-11km/h Force 3 - Gentle Breeze - Leaves and small twigs in motion, wind spreads small flags. 12-19km/h Force 4 - Moderate Breeze - Wind raises dust and loose paper, small branches. 20-29km/h Force 5 - Fresh Breeze - Small leafy trees start to sway, wavelets with crests on inland waters. 30-39km/h Force 6 - Strong Breeze - Large branches in motion, whistling in telephone wires, difficult to use umbrellas. 40-50km/h Force 7 - Near Gale - Whole trees in motion, difficult to walk against wind. 51-61km/h Force 8 - Gale - Twigs break off trees, difficult to walk. 62-74km/h Force 9 - Strong Gale - Slight structual damage to buildings; chimney pots, tiles, and aerials removed. 75-87km/h Force 10 - Storm - Trees prooted, considerable damage to buildings. 88-101km/h Force 11 - Violent Storm - Widespread damage to all types of building. 102-117km/h Force 12 - Hurricane - Widespread destruction, only specially constructed buildings survive. >117km/h

What makes a Thunderstorm? Heat and moisture are key to the formation of thunderstorms. In order to produce the thunder and lightning, you need a cloud tall enough to pull moisture up into the sub-freezing level over 5km/3miles high. These clouds are called cumulus they have a cauliflower like appearance. Cumulus clouds can form any time of the year as long as there is warmth below and coolness above. The process is called convection. Once cumulus clouds reach a height where ice crystals form they become cumulonimbus clouds. The upward motion gradually slows. The stronger upper level winds spread the cloud out at the top, and this formation is called an anvil. As the ice crystals form, they collide with each other and with still-unfrozen water droplets. Electrical charges are produced and eventually the cloud becomes an electric field. If the field becomes more intense lightning is produced. Single-cell Thunderstorm The single-cell thunderstorm (meaning a single updraught) develop and die quickly on summer afternoons. They do not last very long because lackadaisical upper winds which keep them becalmed. Once the rain begins, it cools the air below and cuts of the storms energy in less than half an hour. More single-cell storms can form along the cool air outflowing from older ones or several cells may form together to create the more developed Multicell. Multicell Thunderstorm Multicellular storms consist of a series of evolving cells. At low levels, cooler air diverging from the downdraft intersects the inflowing air along a gust front, creating a region of strong low- level convergence favorable for new updrafts. It is the presence of vertical wind shear that results in the "tilting" of the updraft and downdraft. Because of the tilting, the less buoyant downdraft air will not destroy the updraft and deprive itself up supersaturated updraft air. In any case, the movement of multicell storms systems is determined by combining the new cell development with the mean winds. Each individual cell typically moves with the mean winds, while new cells develop where the inflow meets the outflow in the region of strongest surface, or low-level, convergence. The multicell thunderstorm can drop small hail and produce heavier rain. When a strong cold front is marching through, a squall line may form. This band of connected cells moves through quickly with strong wind, heavy rain, small hail and perhaps even a small tornado. Supercell Thunderstorm The supercell is the biggest of the storm world. These powerful beasts only form when instability is quite strong and, typically, when upper-level winds strengthen with height. This keeps the storm moving and keeps the top of the storm ventilated, so that warm, most air is pulled in from below . We define a supercell as a thunderstorm with a deep rotating updraft (mesocyclone). The major difference between supercell and multicell storms is the element of rotation in supercells. The supercell produces many elements of the strongest thunderstorms which include: Torrential rain, large hail, hurricane-force wind and violent tornadoes. The lifespan of a supercell can reach beyond six hours. Mesoscale Convective Systems (MCS) These are the largest thunderstorm groups on earth. These are a collection of storms - typically organised as a cluster or squall line which can span 100-200 miles and last for more than twelve hours! Partly due to the size of MCSs, they can produce huge amounts of precipitation (250mm/10 inches of rain can fall). MCSs can also generate vast amounts of lightning (Over 10 000 strikes per hour, or about 3 strikes per second). They are more known more known for the spider lightning they produce which stretches from horizon to horizon. MCSS favour the moist heat of the warm season across the mid-latitudes and tropics. In many places, they peak during overnight hours, as smaller storms merge and nocturnal low-level jet streams intensify. If an MCS forms or moves over an ocean, it can serve as the nucleus of a tropical cyclone.