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Updraft
In meteorology, an updraft (British English: ''up-draught'') is a small-scale air current, current of rising air, often within a cloud. Overview Vertical drafts, known as updrafts or downdrafts, are localized regions of warm or cool air that move vertically. A mass of warm air will typically be less dense than the surrounding region, and so will rise until it reaches air that is either warmer or less dense than itself. The converse will occur for a mass of cool air, and is known as Subsidence (atmosphere), subsidence. This movement of large volumes of air, especially when regions of hot, wet air rise, can create large clouds, and is the central source of thunderstorms. Drafts can also be caused by low or high pressure regions. A low pressure region will attract air from the surrounding area, which will move towards the center and then rise, creating an updraft. A high pressure region will attract air from the surrounding area, which will move towards the center and sink, spawning ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Forward Flank Downdraft
A supercell is a thunderstorm characterized by the presence of a mesocyclone, a deep, persistently rotating updraft. Due to this, these storms are sometimes referred to as rotating thunderstorms. Of the four classifications of thunderstorms (supercell, squall line, multi-cell, and single-cell), supercells are the overall least common and have the potential to be the most severe. Supercells are often isolated from other thunderstorms, and can dominate the local weather up to away. They tend to last 2–4 hours. Supercells are often put into three classification types: classic (normal precipitation level), low-precipitation (LP), and high-precipitation (HP). LP supercells are usually found in climates that are more arid, such as the high plains of the United States, and HP supercells are most often found in moist climates. Supercells can occur anywhere in the world under the right pre-existing weather conditions, but they are most common in the Great Plains of the United Stat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thunderstorm Updraft
A thunderstorm, also known as an electrical storm or a lightning storm, is a storm characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere, known as thunder. Relatively weak thunderstorms are sometimes called thundershowers. Thunderstorms occur in cumulonimbus clouds. They are usually accompanied by strong winds and often produce heavy rain and sometimes snow, sleet, or hail, but some thunderstorms can produce little or no precipitation at all. Thunderstorms may line up in a series or become a rainband, known as a squall line. Strong or severe thunderstorms include some of the most dangerous weather phenomena, including large hail, strong winds, and tornadoes. Some of the most persistent severe thunderstorms, known as supercells, rotate as do cyclones. While most thunderstorms move with the mean wind flow through the layer of the troposphere that they occupy, vertical wind shear sometimes causes a deviation in their course at a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thunderstorms
A thunderstorm, also known as an electrical storm or a lightning storm, is a storm characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere, known as thunder. Relatively weak thunderstorms are sometimes called thundershowers. Thunderstorms occur in cumulonimbus clouds. They are usually accompanied by strong winds and often produce heavy rain and sometimes snow, sleet, or hail, but some thunderstorms can produce little or no precipitation at all. Thunderstorms may line up in a series or become a rainband, known as a squall line. Strong or severe thunderstorms include some of the most dangerous weather phenomena, including large hail, strong winds, and tornadoes. Some of the most persistent severe thunderstorms, known as supercells, rotate as do cyclones. While most thunderstorms move with the mean wind flow through the layer of the troposphere that they occupy, vertical wind shear sometimes causes a deviation in their course ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tornado
A tornado is a violently rotating column of air that is in contact with the surface of 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 Hemisphere. Tornadoes come in many shapes and sizes, and they are often (but not always) visible in the form of a funnel cloud, 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 Tornado records#Highest winds observed in a tornado, most extreme tornadoes can attain wind speeds of mo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rear Flank Downdraft
The rear flank downdraft (RFD) is a region of dry air wrapping around the back of a mesocyclone in a supercell thunderstorm. These areas of descending air are thought to be essential in the production of many supercellular tornadoes. Large hail within the rear flank downdraft often shows up brightly as a hook on weather radar images, producing the characteristic ''hook echo'', which often indicates the presence of a tornado. Formation The rear flank downdraft can arise owing to negative buoyancy, which can be generated by cold anomalies produced at the rear of the supercell thunderstorm by evaporative cooling of precipitation or hail melting, or injection of dry and cooler air in the cloud, and by vertical perturbation pressure gradients that can arise from vertical gradients of vertical vorticity, ''stagnation'' of environmental flow at an updraft, and pressure perturbations due to vertical buoyancy variations (which are partially due to hydrostatic effects). Vertical pres ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lee Waves
In meteorology, lee waves are Earth's atmosphere, atmospheric stationary waves. The most common form is mountain waves, which are atmospheric internal gravity waves. These were discovered in 1933 by two German glider pilots, :de:Hans_Deutschmann, Hans Deutschmann and Wolf Hirth, above the Giant Mountains. They are Frequency, periodic changes of atmospheric pressure, temperature and orthometric height in a Air current, current of air caused by vertical displacement, for example orographic lift when the wind blows over a mountain or mountain range. They can also be caused by the surface wind blowing over an escarpment or plateau, or even by upper winds deflected over a thermal updraft or cloud street. The vertical motion forces periodic changes in speed and Boxing the compass, direction of the air within this air current. They always occur in groups on the Windward and leeward, lee side of the terrain that triggers them. Sometimes, mountain waves can help to enhance precipitation a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cloud
In meteorology, a cloud is an aerosol consisting of a visible mass of miniature liquid droplets, frozen crystals, or other particles, suspended in the atmosphere of a planetary body or similar space. Water or various other chemicals may compose the droplets and crystals. On Earth, clouds are formed as a result of saturation of the air when it is cooled to its dew point, or when it gains sufficient moisture (usually in the form of water vapor) from an adjacent source to raise the dew point to the ambient temperature. Clouds are seen in the Earth's homosphere, which includes the troposphere, stratosphere, and mesosphere. Nephology is the science of clouds, which is undertaken in the cloud physics branch of meteorology. The World Meteorological Organization uses two methods of naming clouds in their respective layers of the homosphere, Latin and common name. Genus types in the troposphere, the atmospheric layer closest to Earth's surface, have Latin names because of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Weather Radar
A weather radar, also called weather surveillance radar (WSR) and Doppler weather radar, is a type of radar used to locate precipitation (meteorology), precipitation, calculate its motion, and estimate its type (rain, snow, hail etc.). Modern weather radars are mostly pulse-Doppler radars, capable of detecting the motion of rain droplets in addition to the intensity of the precipitation. Both types of data can be analyzed to determine the structure of storms and their potential to cause severe weather. During Radar in World War II, World War II, radar operators discovered that weather was causing echoes on their screens, masking potential enemy targets. Techniques were developed to filter them, but scientists began to study the phenomenon. Soon after the war, military surplus, surplus radars were used to detect precipitation. Since then, weather radar has evolved and is used by national weather services, research departments in universities, and in television stations' weather d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gliding Meteorology
Gliding is a recreational activity and competitive air sport in which pilots fly unpowered aircraft known as gliders or sailplanes using naturally occurring currents of rising air in the atmosphere to remain airborne. The word ''soaring'' is also used for the sport. Gliding as a sport began in the 1920s. Initially the objective was to increase the duration of flights but soon pilots attempted cross-country flights away from the place of launch. Improvements in aerodynamics and in the understanding of weather phenomena have allowed greater distances at higher average speeds. Long distances are now flown using any of the main sources of rising air: ridge lift, thermals and lee waves. When conditions are favourable, experienced pilots can now fly hundreds of kilometres before returning to their home airfields; occasionally flights of more than are achieved. Some competitive pilots fly in races around pre-defined courses. These gliding competitions test pilots' abilities to mak ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Downburst
In meteorology, a downburst is a strong downward and outward gushing wind system that emanates from a point source above and blows radially, that is, in straight lines in all directions from the area of impact at surface level. It originates under deep, moist convective conditions like cumulus congestus or cumulonimbus. Capable of producing damaging winds, it may sometimes be confused with a tornado, where high-velocity winds circle a central area, and air moves inward and upward. These usually last for seconds to minutes. Downbursts are particularly strong downdrafts within thunderstorms (or deep, moist convection as sometimes downbursts emanate from cumulonimbus or even cumulus congestus clouds that are not producing lightning). Downbursts are most often created by an area of significantly precipitation-cooled air that, after reaching the surface ( subsiding), spreads out in all directions producing strong winds. Dry downbursts are associated with thunderstorms that ex ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Air Current
In meteorology, air currents are concentrated areas of winds. They are mainly due to differences in atmospheric pressure or temperature. They are divided into horizontal and vertical currents; both are present at Mesoscale meteorology, mesoscale while horizontal ones dominate at Synoptic scale meteorology, synoptic scale. Air currents are not only found in the troposphere, but extend to the stratosphere and mesosphere. Horizontal currents A difference in air pressure causes an air displacement and generates the wind. The Coriolis force deflects the air movement to the right in the northern hemisphere and the left in the southern one, which makes the winds parallel to the isobars on an elevation in pressure card. It is also referred as the geostrophic wind. Pressure differences depend, in turn, on the average temperature in the air column. As the sun does not heat the Earth evenly, there is a temperature difference between the poles and the equator, creating air masses with more ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Delta Air Lines Flight 191
Delta Air Lines Flight 191 was a regularly scheduled Delta Air Lines domestic flight from Fort Lauderdale, Florida, to Los Angeles, California, with an intermediate stop at Dallas/Fort Worth International Airport (DFW). On August 2, 1985, the Lockheed L-1011 TriStar operating Flight 191 encountered a microburst while on approach to land at DFW. The aircraft impacted ground just over short of the runway, struck a car near the airport, collided with two water tanks and disintegrated. Out of the 163 occupants on board, 136 people died and 25 others were injured in the accident. One person on the ground also died. The National Transportation Safety Board (NTSB) determined that the crash resulted from the flight crew's decision to fly through a thunderstorm, the lack of procedures or training to avoid or escape microbursts and the lack of hazard information on wind shear. Forecasts of microbursts improved in the following years, with USAir Flight 1016 being the only subsequ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
