|
2019–20 South-West Indian Ocean Cyclone Season
The 2019–20 South-West Indian Ocean cyclone season was a slightly above-average season in tropical cyclone and subtropical cyclone formation west of 90°E. The season officially began on 15 November, however, the formation of the first system—Zone of Disturbed Weather 01—occurred on 22 July 2019, well before the official start of the season. This was the earliest start to a season since the 2016–17 season. The season then officially ended on 30 April 2020, with the exception of Mauritius and the Seychelles, for which it officially ended on 15 May 2020. These dates conventionally delimit the period of each year when most tropical and subtropical cyclones form in the basin, which is west of longitude, 90°E and south of the Equator. Tropical and subtropical cyclones in this basin are monitored by the Regional Specialized Meteorological Centre in Réunion. For the second consecutive year in a row, the first system formed before the official start of the season. After ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
2017–18 South-West Indian Ocean Cyclone Season
The 2017–18 South-West Indian Ocean cyclone season was a below-average season that produced only 8 tropical storms, of which 6 became tropical cyclones. It was an event in the annual cycle of a tropical cyclone and subtropical cyclone formation. It officially began on 15 November 2017, and officially ended on 15 May 2018, in Mauritius and the Seychelles. For the rest of the basin, the season ended on 30 April 2018. These dates conventionally delimit the period of each year when most tropical and subtropical cyclones form in the basin, which is west of 90°E and south of the Equator. Tropical and subtropical cyclones in this basin are monitored by the Regional Specialised Meteorological Centre in La Réunion. __TOC__ Seasonal Summary ImageSize = width:800 height:200 PlotArea = top:10 bottom:80 right:20 left:20 Legend = columns:3 left:30 top:58 columnwidth:250 AlignBars = early DateFormat = dd/mm/yyyy Period = from:01/01/2018 till:01/06/2018 TimeAxis = orientation:h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyclone Herold
Intense Tropical Cyclone Herold was a powerful tropical cyclone that affected Madagascar and the Mascarene Islands in March 2020. Herold was the tenth zone of disturbed weather, ninth depression, eighth moderate tropical storm, sixth severe tropical storm, fifth tropical cyclone, and second intense tropical cyclone of the slightly above-average 2019–20 South-West Indian Ocean cyclone season. Herold formed on 13 March from a disorganized area of low pressure near Tromelin Island.http://www.meteo.fr/temps/domtom/La_Reunion/webcmrs9.0/francais/activiteope/bulletins/zcit/ZCITF_202003011000.pdf When Herold reached Madagascar, it caused five deaths and an unknown amount of damage. Thousands of homes were flooded in the northeastern region. Maroantsetra got the worst of Herold, with all five deaths it caused coming from there. Meteorological history Early in March 2020, an area of low pressure existed near Tromelin Island, but it dissipated on 4 March. It unexpectedly regenerated th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Madden–Julian Oscillation
The Madden–Julian oscillation (MJO) is the largest element of the intraseasonal (30- to 90-day) variability in the tropical atmosphere. It was discovered in 1971 by Roland Madden and Paul Julian of the American National Center for Atmospheric Research (NCAR). It is a large-scale coupling between atmospheric circulation and tropical deep atmospheric convection. Unlike a standing pattern like the El Niño–Southern Oscillation (ENSO), the Madden–Julian oscillation is a traveling pattern that propagates eastward, at approximately , through the atmosphere above the warm parts of the Indian and Pacific oceans. This overall circulation pattern manifests itself most clearly as anomalous rainfall. The Madden–Julian oscillation is characterized by an eastward progression of large regions of both enhanced and suppressed tropical rainfall, observed mainly over the Indian and Pacific Ocean. The anomalous rainfall is usually first evident over the western Indian Ocean, and remains evi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kelvin Wave
A Kelvin wave is a wave in the ocean or atmosphere that balances the Earth's Coriolis force against a topographic boundary such as a coastline, or a waveguide such as the equator. A feature of a Kelvin wave is that it is non-dispersive, i.e., the phase speed of the wave crests is equal to the group speed of the wave energy for all frequencies. This means that it retains its shape as it moves in the alongshore direction over time. A Kelvin wave (fluid dynamics) is also a long scale perturbation mode of a vortex in superfluid dynamics; in terms of the meteorological or oceanographical derivation, one may assume that the meridional velocity component vanishes (i.e. there is no flow in the north–south direction, thus making the momentum and continuity equations much simpler). This wave is named after the discoverer, Lord Kelvin (1879). Coastal Kelvin wave In a stratified ocean of mean depth ''H'', perturbed by some amount ''η'', free waves propagate along coastal boundaries (and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tropical Cyclogenesis
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. Tropical cyclogenesis requires six main factors: sufficiently warm sea surface temperatures (at least ), atmospheric instability, high humidity in the lower to middle levels of the troposphere, enough Coriolis force to develop a low-pressure center, a pre-existing low-level focus or disturbance, and low vertical wind shear. Tropical cyclones tend to develop during the summer, but have been noted in nearly every month in most basins. Climate cycles such as ENSO and the Madden–Julian oscillation modulate the timing and frequency of tropical cyclone development. There is a limit on tropical cyclone i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rodrigues
Rodrigues (french: Île Rodrigues, link=yes ; Creole: ) is a autonomous outer island of the Republic of Mauritius in the Indian Ocean, about east of Mauritius. It is part of the Mascarene Islands, which include Mauritius and Réunion. Rodrigues is of volcanic origin and is surrounded by coral reef, and some tiny uninhabited islands lie just off its coast. The island used to be the tenth District of Mauritius; it gained autonomous status on 10 December 2002, and it is governed by the Rodrigues Regional Assembly. The capital of the island is Port Mathurin. The islands of Rodrigues, Agaléga and Saint Brandon form part of the larger territory of the Republic of Mauritius. Its inhabitants are Mauritian citizens. , the island's population was about 41,669, according to Statistics Mauritius. Most of the inhabitants are of African descent. Its economy is based mainly on fishing, farming, handicraft and a developing tourism sector. Etymology and history The uninhabited island w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wind Shear
Wind shear (or windshear), sometimes referred to as wind gradient, is a difference in wind speed and/or direction over a relatively short distance in the atmosphere. Atmospheric wind shear is normally described as either vertical or horizontal wind shear. Vertical wind shear is a change in wind speed or direction with a change in altitude. Horizontal wind shear is a change in wind speed with a change in lateral position for a given altitude. Wind shear is a microscale meteorological phenomenon occurring over a very small distance, but it can be associated with mesoscale or synoptic scale weather features such as squall lines and cold fronts. It is commonly observed near microbursts and downbursts caused by thunderstorms, fronts, areas of locally higher low-level winds referred to as low-level jets, near mountains, radiation inversions that occur due to clear skies and calm winds, buildings, wind turbines, and sailboats. Wind shear has significant effects on the control of a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tropical Storm
A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure center, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depending on its location and strength, a tropical cyclone is referred to by different names, including hurricane (), typhoon (), tropical storm, cyclonic storm, tropical depression, or simply cyclone. A hurricane is a strong tropical cyclone that occurs in the Atlantic Ocean or northeastern Pacific Ocean, and a typhoon occurs in the northwestern Pacific Ocean. In the Indian Ocean, South Pacific, or (rarely) South Atlantic, comparable storms are referred to simply as "tropical cyclones", and such storms in the Indian Ocean can also be called "severe cyclonic storms". "Tropical" refers to the geographical origin of these systems, which form almost exclusively over tropical seas. "Cyclone" refers to their winds moving in a circle, whirling round ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Numerical Weather Prediction
Numerical weather prediction (NWP) uses mathematical models of the atmosphere and oceans to predict the weather based on current weather conditions. Though first attempted in the 1920s, it was not until the advent of computer simulation in the 1950s that numerical weather predictions produced realistic results. A number of global and regional forecast models are run in different countries worldwide, using current weather observations relayed from radiosondes, weather satellites and other observing systems as inputs. Mathematical models based on the same physical principles can be used to generate either short-term weather forecasts or longer-term climate predictions; the latter are widely applied for understanding and projecting climate change. The improvements made to regional models have allowed for significant improvements in tropical cyclone track and air quality forecasts; however, atmospheric models perform poorly at handling processes that occur in a relatively const ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Convection (meteorology)
Atmospheric convection is the result of a parcel-environment instability, or temperature difference layer in the atmosphere. Different lapse rates within dry and moist air masses lead to instability. Mixing of air during the day which expands the height of the planetary boundary layer leads to increased winds, cumulus cloud development, and decreased surface dew points. Moist convection leads to thunderstorm development, which is often responsible for severe weather throughout the world. Special threats from thunderstorms include hail, downbursts, and tornadoes. Overview There are a few general archetypes of atmospheric instability that are used to explain convection (or lack thereof). A necessary (but not sufficient) condition for convection is that the environmental lapse rate (the rate of decrease of temperature with height) is steeper than the lapse rate experienced by a rising parcel of air. When this condition is met, upward-displaced air parcels can become buoyant an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tropical Cyclone Scales
Tropical cyclones are ranked on one of five tropical cyclone intensity scales, according to their maximum sustained winds and which tropical cyclone basins they are located in. Only a few scales of classifications are used officially by the meteorological agencies monitoring the tropical cyclones, but other scales also exist, such as accumulated cyclone energy, the Power Dissipation Index, the Integrated Kinetic Energy Index, and the Hurricane Severity Index. Tropical cyclones that develop in the Northern Hemisphere are unofficially classified by the warning centres on one of three intensity scales. Tropical cyclones or subtropical cyclones that exist within the North Atlantic Ocean or the North-eastern Pacific Ocean are classified as either tropical depressions or tropical storms. Should a system intensify further and become a hurricane, then it will be classified on the Saffir–Simpson hurricane wind scale, and is based on the estimated maximum sustained winds over a 1-minut ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diego Garcia
Diego Garcia is an island of the British Indian Ocean Territory, a disputed overseas territory of the United Kingdom. It is a militarised atoll just south of the equator in the central Indian Ocean, and the largest of the 60 small islands of the Chagos Archipelago. The Portuguese were the first Europeans to find it and it was then settled by the French in the 1790s and transferred to British rule after the Napoleonic Wars. It was one of the "Dependencies" of the British Colony of Mauritius until the Chagos Islands were detached for inclusion in the newly created British Indian Ocean Territory (BIOT) in 1965. In 1966, the population of the island was 924. These people were employed as contract farm workers primarily on copra plantations owned by the Chagos-Agalega company. Although it was common for local plantation managers to allow pensioners and the disabled to remain in the islands and continue to receive housing and rations in exchange for light work, children after the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
