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Anticyclonic Tornado
An anticyclonic tornado is a tornado which rotates in a clockwise direction in the Northern Hemisphere and a counterclockwise direction in the Southern Hemisphere. The term is a naming convention denoting the anomaly from normal rotation which is cyclonic in upwards of 98 percent of tornadoes. Many anticyclonic tornadoes are smaller and weaker than cyclonic tornadoes, forming from a different process, as either companion/satellite tornadoes or nonmesocyclonic tornadoes. Formation Most strong tornadoes form in the inflow and updraft area bordering the updraft-downdraft interface (which is also near the mesoscale "triple point") zone of supercell thunderstorms. The thunderstorm itself is rotating, with a rotating updraft known as a mesocyclone, and then a smaller area of rotation at lower altitude the tornadocyclone (or low-level mesocyclone) which produces or enables the smaller rotation that is a tornado. All of these may be quasi-vertically aligned continuing from the ground ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tornado
A tornado is a violently rotating column of air that is in contact with both the surface of the Earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. It is often referred to as a twister, whirlwind or cyclone, although the word cyclone is used in meteorology to name a weather system with a low-pressure area in the center around which, from an observer looking down toward the surface of the Earth, winds blow counterclockwise in the Northern Hemisphere and clockwise in the Southern. Tornadoes come in many shapes and sizes, and they are often visible in the form of a condensation funnel originating from the base of a cumulonimbus cloud, with a cloud of rotating debris and dust beneath it. Most tornadoes have wind speeds less than , are about across, and travel several kilometers (a few miles) before dissipating. The most extreme tornadoes can attain wind speeds of more than , are more than in diameter, and stay on the ground for more than 100 k ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyclone
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 (opposite to an anticyclone). 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 (the synoptic 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NEXRAD
NEXRAD or Nexrad (Next-Generation Radar) is a network of 160 high-resolution S-band Doppler weather radars operated by the National Weather Service (NWS), an agency of the National Oceanic and Atmospheric Administration (NOAA) within the United States Department of Commerce, the Federal Aviation Administration (FAA) within the Department of Transportation, and the U.S. Air Force within the Department of Defense. Its technical name is WSR-88D (''Weather Surveillance Radar, 1988, Doppler''). NEXRAD detects precipitation and atmospheric movement or wind. It returns data which when processed can be displayed in a mosaic map which shows patterns of precipitation and its movement. The radar system operates in two basic modes, selectable by the operator – a slow-scanning ''clear-air mode'' for analyzing air movements when there is little or no activity in the area, and a ''precipitation mode'', with a faster scan for tracking active weather. NEXRAD has an increased emphasis on autom ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bow Echo
A bow echo is the characteristic radar return from a mesoscale convective system that is shaped like an archer's bow. These systems can produce severe straight-line winds and occasionally tornadoes, causing major damage. They can also become derechos or form Line echo wave pattern (LEWP). Research The term "bow echo" was first used by Theodore Fujita in his May 1978 paper "Manual of Downburst Identification for Project NIMROD." In 2004, research was done to better anticipate the formation of bow echoes, specifically the formation of bow echoes from weakly organized squall lines and supercells. Researchers determined that bow echoes were most likely to occur in weakly organized cells. A Midwest Bow Echo Workshop was held in 2007, at which meteorologists gathered to share their research to better understand bow echoes. Formation A bow echo is associated with squall lines or lines of convective thunderstorms. These echoes can range in size from 20 to 200 km, and have a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mesovortices
A mesovortex is a small-scale rotational feature found in a convective storm, such as a quasi-linear convective system (QLCS, i.e. squall line), a supercell, or the eyewall of a tropical cyclone. Mesovortices range in diameter from tens of miles to a mile or less and can be immensely intense. Eyewall mesovortex An ''eyewall mesovortex'' is a small-scale rotational feature found in an eyewall of an intense tropical cyclone. Eyewall mesovortices are similar, in principle, to small "suction vortices" often observed in multiple-vortex tornadoes. In these vortices, wind speed can be up to 10% higher than in the rest of the eyewall. Eyewall mesovortices are most common during periods of intensification in tropical cyclones. Eyewall mesovortices often exhibit unusual behavior in tropical cyclones. They usually revolve around the low pressure center, but sometimes they remain stationary. Eyewall mesovortices have even been documented to cross the eye of a storm. These phenomena have been ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rotating Wall Cloud
A wall cloud (murus or pedestal cloud) is a large, localized, persistent, and often abrupt lowering of cloud that develops beneath the surrounding base of a cumulonimbus cloud and from which tornadoes sometimes form. It is typically beneath the rain-free base (RFB) portion of a thunderstorm, and indicates the area of the strongest updraft within a storm. Rotating wall clouds are an indication of a mesocyclone in a thunderstorm; most strong tornadoes form from these. Many wall clouds do rotate; however, some do not. Genesis Wall clouds are formed by a process known as entrainment, when an inflow of warm, moist air rises and converges, overpowering wet, rain-cooled air from the normally downwind downdraft. As the warm air continues to entrain the cooler air, the air temperature drops and the dew point increases (thus the dew point depression decreases). As this air continues to rise, it becomes more saturated with moisture, which results in additional cloud condensation, sometim ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mesoanticyclone
A mesocyclone is a meso-gamma mesoscale (or storm scale) region of rotation (vortex), typically around in diameter, most often noticed on radar within thunderstorms. In the northern hemisphere it is usually located in the right rear flank (back edge with respect to direction of movement) of a supercell, or often on the eastern, or leading, flank of a high-precipitation variety of supercell. The area overlaid by a mesocyclone’s circulation may be several miles (km) wide, but substantially larger than any tornado that may develop within it, and it is within mesocyclones that intense tornadoes form. Description Mesocyclones are medium-scale vortices of rising and converging air that circulate around a vertical axis. They are most often associated with a local region of low-pressure. Their rotation is (usually) in the same direction as low pressure systems in a given hemisphere: counter-clockwise in the northern, and clockwise in the southern hemisphere, with the only occasio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Satellite Tornado
A satellite tornado is a tornado that revolves around a larger, primary tornado and interacts with the same mesocyclone. Satellite tornadoes occur apart from the primary tornado and are not considered subvortices; the primary tornado and satellite tornadoes are considered to be separate tornadoes. The cause of satellite tornadoes is not known. Such tornadoes are more often anticyclonic than are typical tornadoes and these pairs may be referred to as tornado couplets. Satellite tornadoes commonly occur in association with very powerful, large, and destructive tornadoes, indicative also of the strength and severity of the parent supercell thunderstorm. Satellite tornadoes are relatively uncommon. When a satellite tornado does occur, there is often more than one orbiting satellite spawned during the life cycle of the tornado or with successive primary tornadoes spawned by the parent supercell (a process known as cyclic tornadogenesis and leading to a tornado family). On tornado outb ... [...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] |
Cyclonic Rotation
Cyclonic rotation, or cyclonic circulation, is atmospheric motion in the same direction as a planet's rotation, as opposed to anticyclonic rotation. For Earth, the Coriolis effect causes cyclonic rotation to be in a counterclockwise Two-dimensional rotation can occur in two possible directions. Clockwise motion (abbreviated CW) proceeds in the same direction as a clock's hands: from the top to the right, then down and then to the left, and back up to the top. The opposite ... direction in the Northern Hemisphere and clockwise in the Southern Hemisphere. A closed area of winds rotating cyclonically is known as a cyclone. References External linksCyclonic Rotation- AMS Glossary of Meteorology Climate patterns {{climate-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coriolis Effect
In physics, the Coriolis force is an inertial or fictitious force that acts on objects in motion within a frame of reference that rotates with respect to an inertial frame. In a reference frame with clockwise rotation, the force acts to the left of the motion of the object. In one with anticlockwise (or counterclockwise) rotation, the force acts to the right. Deflection of an object due to the Coriolis force is called the Coriolis effect. Though recognized previously by others, the mathematical expression for the Coriolis force appeared in an 1835 paper by French scientist Gaspard-Gustave de Coriolis, in connection with the theory of water wheels. Early in the 20th century, the term ''Coriolis force'' began to be used in connection with meteorology. Newton's laws of motion describe the motion of an object in an inertial (non-accelerating) frame of reference. When Newton's laws are transformed to a rotating frame of reference, the Coriolis and centrifugal accelerations appe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Synoptic Scale
The synoptic scale in meteorology (also known as large scale or cyclonic scale) is a horizontal length scale of the order of 1000 kilometers (about 620 miles) or more. This corresponds to a horizontal scale typical of mid-latitude depressions (e.g., extratropical cyclones). Most high- and low-pressure areas seen on weather maps (such as surface weather analyses) are synoptic-scale systems, driven by the location of Rossby waves in their respective hemisphere. Low-pressure areas and their related frontal zones occur on the leading edge of a trough within the Rossby wave pattern, while high-pressure areas form on the back edge of the trough. Most precipitation areas occur near frontal zones. The word ''synoptic'' is derived from the Greek word ('), meaning ''seen together''. The Navier–Stokes equations applied to atmospheric motion can be simplified by scale analysis in the synoptic scale. It can be shown that the main terms in horizontal equations are Coriolis force and p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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