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Trough (meteorology)

A trough is an elongated region of low atmospheric pressure associated with fronts. Troughs may be at the surface, or aloft, or both under various conditions. Most troughs bring clouds, a wind shift following the passage of the trough; this results from convergence or "squeezing" which forces lifting of moist air behind the trough line. Unlike fronts, there is not a universal symbol for a trough on a weather chart; the weather charts in some countries or regions mark troughs by a line. In the United States, a trough may be marked as bold line. In the UK, Hong Kong and Fiji, it is represented by a bold line extended from a low pressure center or between two low pressure centers. If they are not marked, troughs may still be identified as an extension of isobars away from a low pressure center. A trough is not in a general term a boundary but an elongated area of lower air pressure. There are changes in wind direction across a trough but there is no change in air mass. While not a surface boundary, troughs reflect the change in atmospheric conditions in the upper atmosphere.

As such, troughs can be areas where thunderstorms can form. If a trough forms in the mid-latitudes, a temperature difference at some distance between the two sides of the trough exists and the trough might become a weather front at some point; however such a weather front is less convective than a trough in the tropics or subtropics. Inversely, sometimes collapsed frontal systems will degenerate into troughs. Sometimes the region between two high pressure centers may assume the character of a trough when there is a detectable wind shift noted at the surface. In the absence of a wind shift, the region is designated a col, akin to a geographic saddle between two mountain peaks. A trough is the result of the movements of the air in the atmosphere. In regions where there is upward movement near the ground and divergence at altitude, there is a loss of mass; the pressure becomes lower at this point. At upper levels of the atmosphere, this occurs when there is a meeting of a mass of cold air and another hot one along a thin ribbon called a frontal baroclinic zone.

We have the creation of a jet stream that plunges the cold air towards the equator and hot air towards the poles, creating a ripple in the circulation, called a Rossby wave. These undulations give the peaks of altitude. In general, absolute vorticity advection is positive between these two features, but closer to the ridge, whereas it is negative just behind a trough. At the surface, lifting air under positive vorticity advection is reflected by the formation of depressions and troughs. There will therefore be a slope between the barometric high altitude and that on the ground, this slope going towards the mass of cold air at high altitude. Troughs have an orientation relative to the poles, North-South. In the Northern Hemisphere, positively tilted troughs will extend from the lowest pressure northeast to southwest while negatively tilted troughs have a northwest to southeast orientation. In the Southern Hemisphere, the positive tilt will be southeast to northwest and the negative one southwest to northeast.

A trough will begin with a positive tilt as cold air moves toward the Equator. The trough will become neutral and negatively tilted as the energy carried by the cold air races east though the atmospheric circulation and distorts its shape; the positive tilt is thus the building phase of the trough and the negative tilt is the dissipation of its energy. Therefore, the clouds and precipitation will develop in the positive phase and the most severe weather will be in the negative phase. In addition to standard troughs, some may be described further with a qualifying term indicating a specific or a set of characteristics. An inverted trough is an atmospheric trough, oriented opposite to most troughs of the mid-latitudes. Most inverted troughs are tropical waves. Most troughs of low pressure in the mid-latitudes of the Northern Hemisphere are characterized by decreasing atmospheric pressure from south to north while inverted troughs are characterized by decreasing pressure from north to south; the situation is opposite in the Southern Hemisphere.

Inverted troughs in both hemispheres move to the west from the east, while mid-latitude troughs move with the westerlies toward the east. A lee trough known as a dynamic trough, is "A pressure trough formed on the lee side of a mountain range in situations where the wind is blowing with a substantial component across the mountain ridge, it can be formed either as a result of the adiabatic compression of sinking air on the lee side of a mountain range, or through cyclogenesis resulting from "the horizontal convergence associated with vertical stretching of air columns passing over the ridge and descending the lee slope." Convective cells may give birth to a tropical cyclone. Some tropical or subtropical regions such as the Philippines or south China are affected by convection cells along a trough. In the mid-latitude westerlies, upper level troughs and ridges alternate in a high-amplitude pattern. For a trough in the westerlies, the region just west of the trough axis is an area of convergent winds and descending air – and hence high pressure –, while the region just east of the trough axis is an area of fast, divergent winds and low pressure.

Tropical waves are a t

1997 Beckenham by-election

A by-election in Beckenham, was called in 1997 when the sitting Member of Parliament, Piers Merchant, resigned from Parliament on 21 October 1997. The Conservatives held the seat, with Jacqui Lait winning the by-election on 20 November. Piers Merchant had been under pressure during the May 1997 general election after tabloid newspaper stories about his relationship with a bar hostess whom he had employed as a researcher, but he had denied any impropriety and retained the confidence of his local association, his resignation on 21 October was caused by further newspaper stories and video footage which confirmed that his denial had been misleading. He accepted the office of Crown Bailiff of the Manor of Northstead. At the by-election, the Conservatives selected Jacqui Lait, who had lost her seat at Hastings in the general election; the Labour candidate, Robert Hughes, was a long time resident of the constituency and had contested the seat at the general election. The Liberal Democrats chose their general election candidate Rosemary Vetterlein.

The Conservatives were successful in retaining the seat with a further reduced majority. Held on the same day was a by-election at Winchester; this was the last election. British Parliamentary By Elections: Campaign literature from the by-election

Usman Shehu Bawa

Usman Shehu Bawa, popularly known as Shehu ABG, is a Nigerian politician, a member of the House of Representatives representing Kaduna North constituency. He is a member of the People's Democratic Party. Bawa was born in Nigeria's northern city of Kaduna, he is the son of the founder of Nigeria's ABG Group. He started his primary education at the Kaduna Polytechnic staff school, he was transferred to Kaduna Capital School, where he completed his early education. He began his secondary education at Sardauna Memorial College later on transferred to Essence International School, completing his secondary education in 1993. In 1999, Bawa completed a bachelor's degree in geography at Ahmadu Bello University in Zaria, he started his early professional career working in his father's communication's firm, ABG Communications. He started a number of firms including GSM. COM Limited and Top desk International Limited. While GSM. COM Limited sought to exploit opportunities in the newly deregulated telecommunications industry in 2001, Top Desk International Limited set out as a business consultancy and procurement firm.

Bawa on took a job as general manager of an agricultural firm – Agric Supermarket Limited, a business in which he was a co-founder. Following his decision to join active politics in 2011, Bawa resigned his positions in all the businesses. Bawa is a member of the leading opposition party All Progressives Congress, he started his political career in the All Nigeria Peoples Party where he ran for the House of Representatives to represent Kaduna North Federal Constituency. He joined former Head of State and leading opposition figure, General Muhammadu Buhari to form a new political party - the Congress for Progressive Change, it was on that platform that he ran and won a seat at the lower chamber of the National Assembly in the 2011 general elections. Bawa was appointed as House of Representatives Committee on Communications; the committee has oversight responsibility for the Federal Ministry of Communications Technology and its subsidiary agencies including the Nigerian Communications Commission and Nigerian Postal Service.

During the time he was acting Chairman of the Communications Committee in 2011, Bawa chaired the subcommittee, set up to investigate the SIM Card Registration exercise superintended by the NCC. Usman is member in the some other committees including Diaspora, Navy Banking & Currency, Gas Resources, Electoral Matters, Legislative Compliance, Solid Minerals Development. Bawa was honoured by the APC in Kaduna on September 13, 2014 for showing "exemplary and visionary leadership". Zubairu Shu'una, one of the local leaders of the party in the constituency, presented the certificate of recognition to Bawa, describing him as someone "committed to the uplift of the people"