what type of front has cold air moving into warm air
occluded front
5488591
usually rapid after frontal passage. If the warm air mass is unstable, thunderstorms may be embedded among the stratiform clouds ahead of the front, and after frontal passage thundershowers may continue. On weather maps, the surface location of a warm front is marked with a red line of semicircles pointing in the direction of travel. An occluded front is formed when a cold front overtakes a warm front, and usually forms around mature low-pressure areas. The cold and warm fronts curve naturally poleward into the point of occlusion, which is also known as the triple point. It lies within a
Weather front
815562
half circles pointing in the direction of travel. An occluded front is formed during the process of cyclogenesis when a cold front overtakes a warm front. The cold and warm fronts curve naturally poleward into the point of occlusion, which is also known as the triple point in meteorology. It lies within a sharp trough, but the air mass behind the boundary can be either warm or cold. In a cold occlusion, the air mass overtaking the warm front is cooler than the cool air ahead of the warm front, and plows under both air masses. In a warm occlusion,
Surface weather analysis
12696709
into an area of warmer air in the wake of a developing extratropical cyclone. The warmer air interacts with the cooler air mass along the boundary, and usually produces precipitation. Cold fronts often follow a warm front or squall line. Very commonly, cold fronts have a warm front ahead but with a perpendicular orientation. In areas where cold fronts catch up to the warm front, the occluded front develops. Occluded fronts have an area of warm air aloft. When such a feature forms poleward of an extratropical cyclone, it is known as a trowal, which is short for TRough Of
Cold front
5488592
sharp trough, but the air mass behind the boundary can be either warm or cold. In a cold occlusion, the air mass overtaking the warm front is cooler than the cool air ahead of the warm front and plows under both air masses. In a warm occlusion, the air mass overtaking the warm front is warmer than the cold air ahead of the warm front and rides over the colder air mass while lifting the warm air. A wide variety of weather can be found along an occluded front, with thunderstorms possible, but usually their passage is associated with a
Weather front
10131009
light rain and drizzle due to the fact that, after the warm air rises above the cooler air (which remains on the ground), it gradually cools due to the air's expansion while being lifted, which forms clouds and leads to precipitation. Cold fronts occur when a mass of cooler air dislodges a mass of warm air. This type of transition is sharper, since cold air is more dense than warm air. Precipitation duration is often shorter and generally more intense than that which occurs ahead of warm fronts. A wide variety of weather can be found along an occluded front,
Precipitation types
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Occluded front In meteorology, an occluded front is a weather front formed during the process of cyclogenesis when a cold front overtakes a warm front. When this occurs, the warm air is separated (occluded) from the cyclone center at the Earth's surface. The point where the warm front and the occluded front meet (and consequently the nearest location of warm air to the center of the cyclone) is called the "triple point". The trowal (short for TROugh of Warm air ALoft) is the projection on the Earth's surface of the trough of warm air aloft formed during the occlusion process
Occluded front
535482
cold front over takes the warm front, and reduces the length of the warm front. At this point an occluded front forms where the warm air mass is pushed upwards into a trough of warm air aloft, which is also known as a trowal. Tropical cyclogenesis is the development and strengthening of a tropical cyclone. The mechanisms by which tropical cyclogenesis occurs are distinctly different from those that produce mid-latitude cyclones. Tropical cyclogenesis, the development of a warm-core cyclone, begins with significant convection in a favorable atmospheric environment. There are six main requirements for tropical cyclogenesis: An average of 86
Cyclone
5488591
usually rapid after frontal passage. If the warm air mass is unstable, thunderstorms may be embedded among the stratiform clouds ahead of the front, and after frontal passage thundershowers may continue. On weather maps, the surface location of a warm front is marked with a red line of semicircles pointing in the direction of travel. An occluded front is formed when a cold front overtakes a warm front, and usually forms around mature low-pressure areas. The cold and warm fronts curve naturally poleward into the point of occlusion, which is also known as the triple point. It lies within a
Weather front
3209183
wisdom. Bull. Amer. Meteor. Soc., 92, 443–466, ES19–ES20. Occluded front In meteorology, an occluded front is a weather front formed during the process of cyclogenesis when a cold front overtakes a warm front. When this occurs, the warm air is separated (occluded) from the cyclone center at the Earth's surface. The point where the warm front and the occluded front meet (and consequently the nearest location of warm air to the center of the cyclone) is called the "triple point". The trowal (short for TROugh of Warm air ALoft) is the projection on the Earth's surface of the trough of
Occluded front
3209180
of the depression. Occluded fronts usually form around mature low pressure areas. There are two types of occlusion, warm and cold: The occluded front symbol should thus be plotted at the position where the cold air is intersecting the surface, as on the adjacent image. It thus varies between warm and a cold occlusions. The "trowal" on the other hand, being the projection of the warm air trough aloft, is at the same position in both cases. The position of the occluded front is often misplaced with the associated weather on a weather map but this is the position of
Occluded front
815563
the air mass overtaking the warm front is not as cool as the cold air ahead of the warm front, and rides over the colder air mass while lifting the warm air. A wide variety of weather can be found along an occluded front, with thunderstorms possible, but usually their passage is associated with a drying of the air mass. Occluded fronts are indicated on a weather map by a purple line with alternating half-circles and triangles pointing in direction of travel. Occluded fronts usually form around mature low pressure areas. The trowal is the projection on the Earth's surface
Surface weather analysis
12381873
jet. Bands of thunderstorms can form with sea breeze and land breeze boundaries, if enough moisture is present. If sea breeze rainbands become active enough just ahead of a cold front, they can mask the location of the cold front itself. Once a cyclone occludes, a trough of warm air aloft, or "trowal" for short, will be caused by strong southerly winds on its eastern periphery rotating aloft around its northeast, and ultimately northwestern, periphery (also known as the warm conveyor belt), forcing a surface trough to continue into the cold sector on a similar curve to the occluded front.
Rain
10213705
it couples with the upper level disturbance moving into the cyclone's cold sector. The cold front catches up to the westward portion of the warm front, forming an occluded front. Eventually, the cyclone stacks with the upper level disturbance, becoming isolated within the cold sector, and begins to weaken as it becomes far removed from the original temperature discontinuity along the cold and warm fronts. At this point, it becomes a cold-core low. The frontal boundary becomes weaker and surrounds the equatorward portion of the cyclone, waiting for the next upper level disturbance to form a new low pressure area.
Norwegian cyclone model
3209176
air mass, significant amounts of rain or freezing rain can occur. Stationary fronts will either dissipate after several days or devolve into shear lines, but can change into a cold or warm front if conditions aloft change. Additionally, if one air mass enters the other, then it will change into a cold or warm front, and the stationary front will be reclassified as moving. For instance, if a warm air mass enters a cold air mass, since the advancing air mass is warm, the stationary front will change into a warm front. A stationary front becomes a shear line when
Stationary front
3209178
the front may not move. The two different air masses are then said to be separated by a stationary front. Although the two air masses are not moving, warm air may still rise over the cold air. The slope of a stationary front is as gentle as the slope of a warm front. Weather conditions, too, are similar to those of a warm front. Stationary front A stationary front is a pair of air masses, neither of which is strong enough to replace the other. On a weather map, this is shown by an inter-playing series of white spikes pointing
Stationary front
10213706
A conveyor belt, also referred to as the warm conveyor belt, describes the flow of a stream of warm moist air originating within the warm sector of an extratropical cyclone ahead of the cold front which slopes up above and north of the surface warm front. The idea of the conveyor belt originated in 1969. The left edge of the conveyor belt is sharp due to the higher density air moving in from the west forcing a sharp slope to the cold front. An area of stratiform precipitation develops north of the warm front along the conveyor belt. Active precipitation
Norwegian cyclone model
3209177
the density contrast across the frontal boundary vanishes, usually as a result of temperature equalization, while the narrow zone of wind-shift persists for a time. This is most common over the open ocean as the temperature of the ocean surface is usually the same on both sides of the frontal boundary and modifies the air masses on either side of it to correspond to its own temperature. Stationary fronts always stay still. When a warm or cold front stops moving, it becomes a stationary front. Occasionally cold air and warm air may flow parallel to the front. The position of
Stationary front
815557
wind speed and direction, atmospheric pressure, and often a change in the precipitation pattern. The change is called a front, whether it be warm or cold. Cold fronts develop when cold air masses, usually moving equatorward from the polar region high pressure zones, interact with warm moist air of low pressure systems. The fronts develop at the leading edge of that cold air mass and wrap around (counter-clockwise in the northern hemisphere) about the low pressure zone. A polar front may form approximately along the equatorward edge of the high-level polar jet. Fronts are guided by winds aloft, but they
Surface weather analysis
54649
and Midwest. A blizzard also may be formed when a cold front and warm front mix together and a blizzard forms at the border line. Another storm system occurs when a cold core low over the Hudson Bay area in Canada is displaced southward over southeastern Canada, the Great Lakes, and New England. When the rapidly moving cold front collides with warmer air coming north from the Gulf of Mexico, strong surface winds, significant cold air advection, and extensive wintry precipitation occur. Low pressure systems moving out of the Rocky Mountains onto the Great Plains, a broad expanse of flat
Blizzard
6171526
Polar front In meteorology, the polar front is the boundary between the polar cell and the Ferrel cell around the 60° latitude in each hemisphere. At this boundary a sharp gradient in temperature occurs between these two air masses, each at very different temperatures. The polar front arises as a result of cold polar air meeting warm tropical air. It is a stationary front as the air masses are not moving against each other. Off the coast of eastern North America, especially in winter, there is a sharp temperature gradient between the snow-covered land and the warm offshore currents. The
Polar front
12696708
°C). When cold fronts come through, there is usually a quick, yet strong gust of wind, that shows that the cold front is passing. In surface weather observations, a remark known as FROPA is coded when this occurs. The effects from a cold front can last from hours to days. The air behind the front is cooler than the air it is replacing and the warm air is forced to rise, so it cools. As the cooler air cannot hold as much moisture as warm air, clouds form and rain occurs. Cold fronts form when a cooler air mass moves
Cold front
535481
becomes cyclonic. This rotational flow moves polar air towards the equator on the west side of the low, while warm air move towards the pole on the east side. A cold front appears on the west side, while a warm front forms on the east side. Usually, the cold front moves at a quicker pace than the warm front and "catches up" with it due to the slow erosion of higher density air mass out ahead of the cyclone. In addition, the higher density air mass sweeping in behind the cyclone strengthens the higher pressure, denser cold air mass. The
Cyclone
1902656
east, while warm fronts move poleward. Because of the greater density of air in their wake, cold fronts and cold occlusions move faster than warm fronts and warm occlusions. Mountains and warm bodies of water can slow the movement of fronts. When a front becomes stationary, and the density contrast across the frontal boundary vanishes, the front can degenerate into a line which separates regions of differing wind velocity, known as a shearline. This is most common over the open ocean. Air masses can be modified in a variety of ways. Surface flux from underlying vegetation, such as forest, acts
Air mass
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Warm Air aLoft. A cold front is considered a warm front if it begins to retreat ahead of the next extratropical cyclone along the frontal boundary, and called a stationary front if it stalls. Cold front A cold front is the leading edge of a cooler mass of air, replacing at ground level a warmer mass of air, which lies within a fairly sharp surface trough of low pressure. It forms in the wake of an extratropical cyclone, at the leading edge of its cold air advection pattern, which is also known as the cyclone's dry conveyor belt circulation. Temperature
Cold front
20789447
968 mbar by 12:00 GMT on 23 November. At the same time, a high-pressure anticyclone was pushing into southern England from mainland Europe. There was an unusually strong upper-level temperature gradient between the low- and high-pressure systems, with the low-pressure system funnelling in cold, arctic air from the north, clashing with humid, subtropical air moving up from southern Europe in the anticyclone. During the morning of 23 November, a cold front attached to the southern edge of the low-pressure area began to cross the United Kingdom from west to east. Fuelled by this temperature gradient and warm subtropical air to
1981 United Kingdom tornado outbreak
712082
then begin saltating. This process has been found to double the number of particles predicted by previous theories. Particles become loosely held mainly due to a prolonged drought or arid conditions, and high wind speeds. Gust fronts may be produced by the outflow of rain-cooled air from an intense thunderstorm. Or, the wind gusts may be produced by a dry cold front, that is, a cold front that is moving into a dry air mass and is producing no precipitation—the type of dust storm which was common during the Dust Bowl years in the U.S. Following the passage of a
Dust storm
3209160
Warm front A warm front is a density discontinuity located at the leading edge of a homogeneous warm air mass, and is typically located on the equator-facing edge of an isotherm gradient. Warm fronts lie within broader troughs of low pressure than cold fronts, and move more slowly than the cold fronts which usually follow because cold air is denser and less easy to remove from the Earth's surface. This also forces temperature differences across warm fronts to be broader in scale. Clouds ahead of the warm front are mostly stratiform, and rainfall gradually increases as the front approaches. Fog
Warm front
5488601
shear and the presence of a strong jet stream, "roll clouds" and tornadoes may occur. In the warm season, lee troughs, breezes, outflow boundaries and occlusions can lead to convection if enough moisture is available. "Orographic precipitation" is precipitation created through the lifting action of air moving over terrain such as mountains and hills, which is most common behind cold fronts that move into mountainous areas. It may sometimes occur in advance of warm fronts moving northward to the east of mountainous terrain. However, precipitation along warm fronts is relatively steady, as in rain or drizzle. Fog, sometimes extensive and
Weather front
19723573
or health effects caused by air pollution. In November 1966, New York City was experiencing an unseasonably warm "Indian summer". A cold front from Canada brought clean air to the city on November19, but the cold front was held in place by pressure from the higher atmosphere. An anticyclonic temperature inversion—in other words, a warm, mostly stationary air mass located atop a cooler air mass—formed over the East Coast on November 20. Unlike atmospheric convection—the ordinary process of lower, warm air rising—inversions leave cooler air suspended below warm air, preventing the lower air from rising and trapping airborne pollutants that
1966 New York City smog
5488588
trough. Cold fronts often bring heavy thunderstorms, rain, and hail. Cold fronts can produce sharper changes in weather and move up to twice as quickly as warm fronts, since cold air is denser than warm air and rapidly replaces the warm air preceding the boundary. On weather maps, the surface position of the cold front is marked with the symbol of a blue line of triangle-shaped pips pointing in the direction of travel, and it is placed at the leading edge of the cooler air mass. Cold fronts come in association with a low-pressure area. The concept of colder, dense
Weather front
5488594
lines. A stationary front is a non-moving (or stalled) boundary between two air masses, neither of which is strong enough to replace the other. They tend to remain essentially in the same area for extended periods of time, usually moving in waves. There is normally a broad temperature gradient behind the boundary with more widely spaced isotherm packing. A wide variety of weather can be found along a stationary front, but usually clouds and prolonged precipitation are found there. Stationary fronts either dissipate after several days or devolve into shear lines, but they can transform into a cold or warm
Weather front
8789900
mid-tropospheric trough persisted over the western Caribbean Sea in late May. Around that time, a short-wave trough moving eastward through the Caribbean Sea forced a cold front to move southward into the Straits of Florida. Satellite imagery indicated that the cold front and mid-tropospheric trough began merging as the low-level convergence field increased. Thereafter, barometric pressures in the western Caribbean were decreasing as deep southwesterly flow caused very warm and moist air to enter the area. At 0600 UTC on June 1, the system developed into Tropical Depression One, while situated about northeast of Guanaja, Honduras. When a weak cold
Hurricane Abby (1968)
5488590
leading edge of a homogeneous warm air mass, which is located on the equatorward edge of the gradient in isotherms, and lie within broader troughs of low pressure than cold fronts. A warm front moves more slowly than the cold front which usually follows because cold air is denser and harder to remove from the Earth's surface. This also forces temperature differences across warm fronts to be broader in scale. Clouds ahead of the warm front are mostly stratiform, and rainfall gradually increases as the front approaches. Fog can also occur preceding a warm frontal passage. Clearing and warming is
Weather front
20774358
an existing rack. These heat exchangers leverage the front-to-back air dissipation of most of the IT equipments: the servers dissipate warm air, which passes the heat exchanger coil and is returned to the room at an agreeable temperature. The cooling units of this category do not occupy additional space, so they are particularly indicated either to cool all the spaces originally designed as data centers, or to integrate an already existing cooling system. Generally, a heat exchanger of this type discharges air from the ceiling into the cold aisle whereas the exhaust air rises into the vents in the ceiling;
Close Coupled Cooling
6171527
polar front theory says that mid-latitude cyclones form on boundaries between warm and cold air. In winter, the polar front shifts towards the Equator, whereas high pressure systems dominate more in the summer. Polar front In meteorology, the polar front is the boundary between the polar cell and the Ferrel cell around the 60° latitude in each hemisphere. At this boundary a sharp gradient in temperature occurs between these two air masses, each at very different temperatures. The polar front arises as a result of cold polar air meeting warm tropical air. It is a stationary front as the air
Polar front
3209185
across the High Plains states in the warm sector of an extratropical cyclone and stretches into the Canadian Prairies during the spring and early summer. The dry line is also important for severe convective storms in other regions of the world, such as northern India. Near the surface, warm dry air is more dense than warm moist air of lesser or similar temperature, and thus the warm dry air wedges under the moist air like a cold front. At higher altitudes, the warm moist air is less dense than the cooler, drier air and the boundary slope reverses. In the
Dry line
12696701
blue line of triangles/spikes (pips) pointing in the direction of travel. A cold front's location is at the leading edge of the temperature drop off, which in an isotherm analysis would show up as the leading edge of the isotherm gradient, and it normally lies within a sharp surface trough. Cold fronts move faster than warm fronts and can produce sharper changes in weather. Since cold air is denser than warm air, it rapidly replaces the warm air preceding the boundary. In the northern hemisphere, a cold front usually causes a shift of wind from southwest to northwest clockwise, also
Cold front
4154682
into a tornado outbreak at around 11 am on May 31. Overall, the derecho traveled from southern Minnesota to central New York in 15 hours at an average speed of . It became one of the most damaging derecho events in North America's history, causing $300 million in damage. On Sunday, May 31, Friday's cold front, which stalled over southern Pennsylvania, started moving quickly back northward as a warm front as strong low pressure approached the Great Lakes. North of the warm front, most of the Hudson Valley and Western New England were under a cool and stable marine air
Late-May 1998 tornado outbreak and derecho
3793960
cold front with warm moisture-laden air from the Gulf of Mexico. Within a few hours, the advancing cold front caused a temperature drop from a few degrees above freezing to −20 degrees Fahrenheit (-29 degrees Celsius) [ in some places]. This wave of cold was accompanied by high winds and heavy snow. The fast-moving storm first struck Montana in the early hours of January 12, swept through Dakota Territory from midmorning to early afternoon, and reached Lincoln, Nebraska at 3 p.m. Many who were caught unaware misjudged the weather due to a warm spell. Carl Saltee, a teenage Norwegian immigrant
Schoolhouse Blizzard
7517537
chimneys leading. This tighter envelope means the air temperature in buildings has risen, the warmer the air in the building is, the more water vapour the air can carry. As the occupied part of building has become warner, the roof space has become colder, with high performance insulation and roofing membranes leading to a cold roof space. When the warm, moist air from below rises into the cold roof space; condensation begins as the air temperature drops to the ‘dew point’ or as the warm air comes into contact with any of the cold surfaces in the roof. Most building
Domestic roof construction
582515
stratiform clouds over a wide area unless the approaching warm airmass is unstable, in which case cumulus congestus or cumulonimbus clouds will usually be embedded in the main precipitating cloud layer. Cold fronts are usually faster moving and generate a narrower line of clouds which are mostly stratocumuliform, cumuliform, or cumulonimbiform depending on the stability of the warm air mass just ahead of the front. Another agent is the convective upward motion of air caused by daytime solar heating at surface level. Airmass instability allows for the formation of cumuliform clouds that can produce showers if the air is sufficiently
Cloud
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variety of causes for forming. Topography can force a surface low when dense low-level high pressure system ridges in east of a north-south mountain barrier. Mesoscale convective systems can spawn surface lows which are initially warm core. The disturbance can grow into a wave-like formation along the front and the low will be positioned at the crest. Around the low, flow will become cyclonic, by definition. This rotational flow will push polar air equatorward west of the low via its trailing cold front, and warmer air will push poleward low via the warm front. Usually the cold front will move
Cyclogenesis
14019130
of the surface warm front. The concept of the conveyor belt originated in 1969. The left edge of the conveyor belt is sharp due to higher density air moving in from the west forcing a sharp slope to the cold front. An area of stratiform precipitation develops poleward of the warm front along the conveyor belt. Active precipitation poleward of the warm front implies potential for greater development of the cyclone. A portion of this conveyor belt turns to the right (left in the Southern Hemisphere), aligning with the upper level westerly flow. However, the western portion of this belt
Inflow (meteorology)
815559
as the leading edge of the isotherm gradient, and it normally lies within a sharp surface trough. Cold fronts can move up to twice as fast as warm fronts and produce sharper changes in weather, since cold air is denser than warm air and rapidly lifts the warm air as the cold air moves in. Cold fronts are typically accompanied by a narrow band of showers and thunderstorms. On a weather map, the surface position of the cold front is marked with the symbol of a blue line of triangles/spikes (pips) pointing in the direction of travel, at the leading
Surface weather analysis
16057061
Interstitial condensation Interstitial condensation is a form of structural damping that occurs when warm, moist air penetrates inside a wall, roof or floor structure, reaches the dew point and condenses into liquid water. Interstitial condensation is differentiated from surface condensation in buildings sometimes called "cold-bridge condensation" or "warm front condensation" where the condensation forms on the interior or exterior surfaces of a building rather than inside the wall or roof cavities. The warm, damp air may penetrate a wall from the inside of a heated building in a cold climate or from the exterior of an air-conditioned building in a
Interstitial condensation
5488583
passage. Some fronts produce no precipitation and little cloudiness, although there is invariably a wind shift. Cold fronts and occluded fronts generally move from west to east, while warm fronts move poleward. Because of the greater density of air in their wake, cold fronts and cold occlusions move faster than warm fronts and warm occlusions. Mountains and warm bodies of water can slow the movement of fronts. When a front becomes stationary—and the density contrast across the frontal boundary vanishes—the front can degenerate into a line which separates regions of differing wind velocity, known as a shearline. This is most
Weather front
1902655
phenomena. In surface weather analyses, fronts are depicted using various colored lines and symbols, depending on the type of front. The air masses separated by a front usually differ in temperature and humidity. Cold fronts may feature narrow bands of thunderstorms and severe weather, and may on occasion be preceded by squall lines or dry lines. Warm fronts are usually preceded by stratiform precipitation and fog. The weather usually clears quickly after a front's passage. Some fronts produce no precipitation and little cloudiness, although there is invariably a wind shift. Cold fronts and occluded fronts generally move from west to
Air mass
1737657
Capping inversion A capping inversion is an elevated inversion layer that caps a convective boundary layer. The boundary layer is the part of the atmosphere which is closest to the ground. Normally, the sun heats the ground, which in turn heats the air just above it. Thermals form when this warm air rises into the cold air (warm air is less dense than cold air), a process described by convection. A convective layer such as this has the potential for cloud formation, since condensation occurs as the warm air rises and cools. An inversion occurs when the normal temperature (warm
Capping inversion
11939269
the passage of a front) that is responsible for bringing cold air from the south. Thus, invasions of cold air from the south are more common during La Niña events. In contrast, warm spells in the Pampas and northern parts of the country are more intense and frequent during El Niño events. This is due to stronger westerly winds south of 40S, leading to less frequent incursions of cold air from the south while enhancing winds from the north that bring in warm air. Although La Niña events lead to colder winters with more frequent incursions of cold air in
Climate of Argentina
2786372
produce no precipitation and little cloudiness, although there is invariably a wind shift. Cold fronts and occluded fronts generally move from west to east, while warm fronts move poleward. Because of the greater density of air in their wake, cold fronts and cold occlusions move faster than warm fronts and warm occlusions. Mountains and warm bodies of water can slow the movement of fronts. When a front becomes stationary, and the density contrast across the frontal boundary vanishes, the front can degenerate into a line which separates regions of differing wind velocity, known as a shearline. This is most common
Synoptic scale meteorology
815567
a manner similar to that of a cold front wedging under warmer air. When the warm moist air wedged under the drier mass heats up, it becomes less dense and rises and sometimes forms thunderstorms. At higher altitudes, the warm moist air is less dense than the cooler, drier air and the boundary slope reverses. In the vicinity of the reversal aloft, severe weather is possible, especially when a triple point is formed with a cold front. During daylight hours, drier air from aloft drifts down to the surface, causing an apparent movement of the dryline eastward. At night, the
Surface weather analysis
1737658
air below, cold air above) profile is reversed, creating a stable configuration of dense, cold air sitting below lighter, warm air. An elevated inversion layer is thus a region of warm air above a region of cold air, but higher in the atmosphere (generally not touching the surface). A capping inversion occurs when there is a boundary layer with a normal temperature profile (warm air rising into cooler air) and the layer above that is an inversion layer (cooler air below warm air). Cloud formation from the lower layer is "capped" by the inversion layer. If the capping inversion layer
Capping inversion
2529672
Some intakes use heat shields to isolate the air filter from the rest of the engine compartment, providing cooler air from the front or side of the engine bay. This can make a big difference to intake temperatures, especially when the car is moving slowly. Some systems, called "fender mount," move the filter into the fender wall instead. This system draws air up through the fender wall which provides even more isolation and still cooler air. Cold air intake A cold air intake (CAI) is usually an aftermarket assembly of parts used to bring relatively cool air into a car's
Cold air intake
14739678
meandered northeastward. Following the entry of cool sea air, however, it recurved to the southeast before transitioning into a Saharan depression associated with a distinct cold front by 22 September. Along the front's path, desert air moved northward while cold air drifted in the opposite direction, and in northern Libya, warm arid air clashed with the cooler levant of the Mediterranean. The organization of the disturbance improved slightly further before emerging into the Mediterranean Sea on 23 September, upon which the system experienced immediate cyclogenesis, rapidly intensifying while southeast of Malta as a cold-core cut-off low, and acquiring tropical characteristics.
Mediterranean tropical-like cyclone
5488582
Weather front A weather front is a boundary separating two masses of air of different densities, and is the principal cause of meteorological phenomena outside the tropics. In surface weather analyses, fronts are depicted using various colored triangles and half-circles, depending on the type of front. The air masses separated by a front usually differ in temperature and humidity. Cold fronts may feature narrow bands of thunderstorms and severe weather, and may on occasion be preceded by squall lines or dry lines. Warm fronts are usually preceded by stratiform precipitation and fog. The weather usually clears quickly after a front's
Weather front
3209167
and speed remains steady. On weather maps, the surface location of a warm front is marked with a red line of half circles pointing in the direction of the front. On colored weather maps, warm fronts are illustrated with a solid red line. Warm front A warm front is a density discontinuity located at the leading edge of a homogeneous warm air mass, and is typically located on the equator-facing edge of an isotherm gradient. Warm fronts lie within broader troughs of low pressure than cold fronts, and move more slowly than the cold fronts which usually follow because cold
Warm front
54648
1880–81. In the United States, storm systems powerful enough to cause blizzards usually form when the jet stream dips far to the south, allowing cold, dry polar air from the north to clash with warm, humid air moving up from the south. When cold, moist air from the Pacific Ocean moves eastward to the Rocky Mountains and the Great Plains, and warmer, moist air moves north from the Gulf of Mexico, all that is needed is a movement of cold polar air moving south to form potential blizzard conditions that may extend from the Texas Panhandle to the Great Lakes
Blizzard
5488596
differences. When the westerlies increase on the north side of surface highs, areas of lowered pressure will form downwind of north–south oriented mountain chains, leading to the formation of a lee trough. Near the surface during daylight hours, warm moist air is denser than dry air of greater temperature, and thus the warm moist air wedges under the drier air like a cold front. At higher altitudes, the warm moist air is less dense than the dry air and the boundary slope reverses. In the vicinity of the reversal aloft, severe weather is possible, especially when a triple point is
Weather front
815560
edge of the cooler air mass. Warm fronts mark the position on the Earth's surface where a relatively warm body of air has displaced colder air. The temperature increase is located on the equatorward edge of the gradient in isotherms, and lies within broader low pressure troughs than is the case with cold fronts. Warm fronts move more slowly than do the cold fronts because cold air is denser, and harder to displace from the Earth's surface. This causes temperature differences across warm fronts to be broader in scale. The warm air mass overrides the cold air mass and temperature
Surface weather analysis
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air "wedging" under the less dense warmer air is often used to depict how air is lifted along a frontal boundary. The cold air wedging underneath warmer air creates the strongest winds just above the ground surface, a phenomenon often associated with property-damaging wind gusts. This lift would then form a narrow line of showers and thunderstorms if enough moisture were present. However, this concept isn't an accurate description of the physical processes; upward motion is not produced because of warm air "ramping up" cold, dense air, rather, frontogenetical circulation is behind the upward forcing. Warm fronts are at the
Weather front
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line contour. A weather front is a boundary separating two masses of air of different densities, and is the principal cause of meteorological phenomena. In surface weather analyses, fronts are depicted using various colored lines and symbols, depending on the type of front. The air masses separated by a front usually differ in temperature and humidity. Cold fronts may feature narrow bands of thunderstorms and severe weather, and may on occasion be preceded by squall lines or dry lines. Warm fronts are usually preceded by stratiform precipitation and fog. The weather usually clears quickly after a front's passage. Some fronts
Synoptic scale meteorology
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of the damage. The term downdraft can also refer to a type of backdraft which occurs through chimneys which have fireplaces on the lowermost levels (such as basements) of multi-level buildings. It involves cold air coming down the chimney due to low air pressure, and makes it hard to light fires, and can push soot and carbon monoxide into domiciles. Vertical draft An updraft is a small‐scale current of rising air, often within a cloud. Localized regions of warm or cool air will exhibit vertical movement. A mass of warm air will typically be less dense than the surrounding region,
Vertical draft
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they make contact with the ground, due to their differing mechanics from true mesoform tornadoes. Though usually weaker than classic tornadoes, they can produce strong winds which could cause serious damage. A "gustnado", or "gust front tornado", is a small, vertical swirl associated with a gust front or downburst. Because they are not connected with a cloud base, there is some debate as to whether or not gustnadoes are tornadoes. They are formed when fast moving cold, dry outflow air from a thunderstorm is blown through a mass of stationary, warm, moist air near the outflow boundary, resulting in a
Tornado
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Cold air intake A cold air intake (CAI) is usually an aftermarket assembly of parts used to bring relatively cool air into a car's internal-combustion engine. Most vehicles manufactured from the mid-1970s until the mid-1990s have thermostatic air intake systems that regulate the temperature of the air entering the engine's intake tract, providing warm air when the engine is cold and cold air when the engine is warm to maximize performance, efficiency, and fuel economy. With the advent of advanced emission controls and more advanced fuel injection methods modern vehicles do not have a thermostatic air intake system and the
Cold air intake
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drying of the air mass. Within the occlusion of the front, a circulation of air brings warm air upward and sends drafts of cold air downward, or vice versa depending on the occlusion the front is experiencing. Precipitations and clouds are associated with the "trowal", the projection on the Earth's surface of the tongue of warm air aloft formed during the occlusion process of the depression. Occluded fronts are indicated on a weather map by a purple line with alternating half-circles and triangles pointing in direction of travel. The trowal is indicated by a series of blue and red junction
Weather front
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the U.S. Tornadoes often form when cool, polar air traveling southeastward from the Rockies overrides warm, moist, unstable Gulf of Mexico air in the eastern states. Tornadoes therefore tend to be commonly found in front of a cold front, along with heavy rains, hail, and damaging winds. Since both warm and cold weather are common during the springtime, the conflict between these two air masses tends to be most common in the spring. As the weather warms across the country, the occurrence of tornadoes spreads northward. Tornadoes are also common in the summer and early fall because they can also
Tornado climatology
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of Mexico. This is due to cold air moving southward reaching its southern limit of expansion, and stopping over the Gulf Coast. As spring comes, hot air progressively moves back into the Gulf Coast. This pushes the mass of colder air forward out of the Gulf States and into the Southeastern states, where tornado frequency is highest in April. As spring passes and summer begins, the mass of warm moist air moves northwest into the Great Plains and Midwestern states. During the months of May and June, tornado activity is as its peak in the southern Great Plains. The air
Tornadoes in the United States
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Inflow (meteorology) Inflow is the flow of a fluid into a large collection of that fluid. Within meteorology, inflow normally refers to the influx of warmth and moisture from air within the Earth's atmosphere into storm systems. Extratropical cyclones are fed by inflow focused along their cold front and warm fronts. Tropical cyclones require a large inflow of warmth and moisture from warm oceans in order to develop significantly, mainly within the lowest of the atmosphere. Once the flow of warm and moist air is cut off from thunderstorms and their associated tornadoes, normally by the thunderstorm's own rain-cooled outflow
Inflow (meteorology)
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or Hurricane Katrina. The American Red Cross, The Salvation Army, Save the Children, the United Way, the Air Land Emergency Resource Team, Boulder Flood Relief, and Helping Pets are among the organizations accepting donations on behalf of flood victims. 2013 Colorado floods The 2013 Colorado floods were a series of natural disasters occurring in the U.S. state of Colorado. Starting on September 9, 2013, a slow-moving cold front stalled over Colorado, clashing with warm humid monsoonal air from the south. This resulted in heavy rain and catastrophic flooding along Colorado's Front Range from Colorado Springs north to Fort Collins. The
2013 Colorado floods
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and in the southern hemisphere a shift from winds blowing from northeast to northwest. Common characteristics associated with warm fronts include: The warm sector is the area of warmer air behind a warm front, usually between the warm and cold fronts in a depression. Temperatures are often warmer than they are before the warm front or after the cold front. Cloud types can be mixed, but usually consist of stratocumulus, which can range to being broken to covering the entire sky depending on distance from the centre of low pressure. Temperature rises and the dew point remains steady. Wind direction
Warm front
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the airfoil and flight control surfaces. (See atmospheric icing.) Freezing rain is often associated with the approach of a warm front, when subfreezing air (temperatures at or below freezing) is trapped in the lowest levels of the atmosphere while warm air advects in aloft. This happens, for instance, when a low pressure system moves from the Mississippi River Valley toward the Appalachian Mountains and the Saint Lawrence River Valley of North America during the cold season, with a strong high pressure system sitting further east. This setup is known as cold-air damming, and is characterized by very cold and dry
Freezing rain
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storms and tornado threat, but usually fewer and less severe than in spring. Each spring, cold fronts moving south from the North will collide with warm, humid air streaming in from the Gulf Coast, leading to severe thunderstorms with lightning, torrents of rain, hail, and occasionally, tornadoes. Over time, tornadoes have probably been the most significant natural threat to the city, as it is near the heart of Tornado Alley. A few times each winter in Dallas, warm and humid air from the south will override cold, dry air, resulting in freezing rain or ice and causing disruptions in the
Dallas
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with seasons, building strength when moving southward during the winter and spring, and weakening when moving northward during the summer. The North Pacific subtropical fronts are occupied by wind driven submesoscale subduction. Due to the constant thermohaline circulation fronts, cold air flows near the surface and bottom of the ocean. There are alternating fluxes throughout the year, that is influenced by jet streams which causes temperatures in these areas to differ. The Southern subtropical front is caused by warm, salty subtropical waters and Antarctic waters, found in all three ocean basins. A commonly used criterion found is that the salinity
Subtropical front
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with many possible factors affecting the development of thundersnow. The best location in a storm to find thundersnow is typically in its NorthWest quadrant (in the Northern Hemisphere, based on observations in the Midwestern United States), within what is known as the "comma head" of a mature extratropical cyclone. Thundersnow can also be located underneath the TROWAL, a trough of warm air aloft which shows up in a surface weather analysis as an inverted trough extending backward into the cold sector from the main cyclone. In extreme cases, thunderstorms along the cold front are transported towards the center of the
Thundersnow
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that the identities of the fluids are reversed. The Boussinesq approximation is "inaccurate" when the dimensionless density difference is of order unity. For example, consider an open window in a warm room. The warm air inside is less dense than the cold air outside, which flows into the room and down towards the floor. Now imagine the opposite: a cold room exposed to warm outside air. Here the air flowing in moves up toward the ceiling. If the flow is Boussinesq (and the room is otherwise symmetrical), then viewing the cold room upside down is exactly the same as viewing
Boussinesq approximation (buoyancy)
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is attached to the base of the parent cloud, which is usually a thunderstorm cumulonimbus, but could form on any type of convective clouds. Rising cloud motion often can be seen in the leading (outer) part of the shelf cloud, while the underside often appears turbulent and wind-torn. Cool, sinking air from a storm cloud's downdraft spreads out across the land surface, with the leading edge called a gust front. This outflow cuts under warm air being drawn into the storm's updraft. As the lower cooler air lifts the warm moist air, its water condenses, creating a cloud which often
Arcus cloud
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of the low became known as either the steering line or the warm front. The trailing convergence zone was referred to as the squall line or cold front. Areas of clouds and rainfall appeared to be focused along these convergence zones. A conveyor belt, also referred to as the warm conveyor belt, is a term describing the flow of a stream of warm moist air originating within the warm sector (or generally equatorward) of an extratropical cyclone in advance of the cold front which slopes up above and poleward (north in the Northern Hemisphere and south in the Southern Hemisphere)
Inflow (meteorology)
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dense, often occurs in pre-warm-frontal areas. Although, not all fronts produce precipitation or even clouds because moisture must be present in the air mass which is being lifted. Fronts are generally guided by winds aloft, but do not move as quickly. Cold fronts and occluded fronts in the Northern Hemisphere usually travel from the northwest to southeast, while warm fronts move more poleward with time. In the Northern Hemisphere a warm front moves from southwest to northeast. In the Southern Hemisphere, the reverse is true; a cold front usually moves from southwest to northeast, and a warm front moves from
Weather front
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result. Sleet, or Ice pellets, form when a layer of above-freezing air exists with sub-freezing air both above and below it. This causes the partial or complete melting of any snowflakes falling through the warm layer. As they fall back into the sub-freezing layer closer to the surface, they re-freeze into ice pellets. However, if the sub-freezing layer beneath the warm layer is too small, the precipitation will not have time to re-freeze, and freezing rain will be the result at the surface. A thicker or stronger cold layer, where the warm layer aloft does not significantly warm above the
Cold-air damming
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rainfall on the southern side of the Alps (northern side of the Alps when there is a north föhn). The föhn-like high altitude winds are mostly large-scale, central Atlantic or African air masses from the southwest to south, which cause unusually warm conditions north of the Alps even at low wind speeds. Triggers are usually slow-moving or blocked Atlantic depressions in the area of the British Isles and North Sea, which move air radially at their outside edge, i.e. the cold front. In particularly extreme conditions, however, this also results in a valley föhn. They are föhn-like inasmuch as the
Alpine föhn
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1996 Southern Ontario tornadoes Southern Ontario's worst tornado outbreak of the decade came on Saturday, April 20, 1996. Severe weather had raked parts of the U.S. Midwest the day before, where seventeen F2 or greater tornadoes touched down (ten in Illinois alone). A cold front was being dragged eastward into unusually warm and unstable air associated with a strong storm system moving through the northern tier of the U.S. Out of the two significant tornadoes that day, both rated F3, it was remarkable that no lives were lost. Nine people escaped with minor injuries. Many homes were severely damaged in
1996 Southern Ontario tornadoes
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the Custer expedition in nearby French Creek and the subsequent founding of the town. According to the United States Census Bureau, the city has a total area of , of which, is land and is water. Custer has been assigned the ZIP code 57730 and the FIPS place code 15140. Its primary telephone prefix is 673 in area code 605. Custer has a humid continental climate (Köppen "Dfb") with summers featuring very warm afternoons and cool mornings, and cold, extremely variable winters. Winter weather is dominated by the conflict between cold Arctic air moving south from Canada, and very warm
Custer, South Dakota
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(but not always) also higher in humidity than the colder air preceding it. Because of a warm air mass’s higher temperature and thus lesser density, mixing between the two air masses is unlikely. Being light, the warm air mass is unable to displace the cooler air mass and instead is forced upward along the upper boundary of the colder air in a process known as overrunning. The boundary between the two air masses has a gradual slope of 1:200 and lifting is slow but persistent. As the air mass rises into regions of lower pressure, it expands and cools. As
Warm front
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Missouri traveled for , but did not cause any significant damage. On April 24, an energetic upper level storm system strengthened as it moved from Texas to the southern Great Lakes Region. A cold front moved eastward across the middle and lower Mississippi River Valley before heading into the Ohio River Valley and stretched into the Mid-South portion of the United States. In front of the cold front, a warm, moist and unstable air mass spread northward from the lower Mississippi River Valley and northern Gulf Coast States into the middle Mississippi and Ohio River Valleys. There were already thunderstorms
Tornado outbreak of April 22–25, 2010
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the boundary of the cold air – often indicated as a coastal or warm front – will move inland, diminishing the width of the cold dome. An objective scheme has been developed to classify certain types of CAD events in the Southeastern United States. Each scheme is based on the strength and location of the parent high-pressure system. Classical CAD events are characterized by dry synoptic forcing, partial diabatic contribution, and a strong parent anticyclone (high-pressure system) located to the north of the Appalachian damming region. A strong high-pressure system usually is defined as having a central pressure over .
Cold-air damming
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to Edmonton's southern boundary. In the week preceding July 31, a low pressure system sitting over southwestern British Columbia fed warm, humid air into central Alberta. Daytime heating along with near-record dewpoints over Alberta triggered a series of strong thunderstorms that persisted throughout the week. On July 31, a cold front developed over western Alberta, colliding with the warm moist air that persisted over the region. Forecasters recognized the elevated risk for severe weather early in the day. Weatheradio broadcasts and interviews with the media stressed "vicious thunderstorms" and "extremely strong and violent thunderstorms". Severe thunderstorms developed rapidly over the
Edmonton tornado
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three linear squall bands pass in rapid succession only separated by 25 miles (40 kilometers) with each passing the same point in roughly 30 minutes apart. In cases where there is a large amount of vertical growth and mixing the squall may develop embedded cumulonimbus clouds resulting in lightning and thunder which is dubbed thundersnow. A warm front can produce snow for a period, as warm, moist air overrides below-freezing air and creates precipitation at the boundary. Often, snow transitions to rain in the warm sector behind the front. Lake-effect snow is produced during cooler atmospheric conditions when a cold
Snow
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Ontario, Canada, by 2:00 pm on December 20, when a freezing rain warning was in place. The associated warm front, which ran from Texas, met a cold air mass in eastern Canada, where large amounts of snow fell. Near the front, precipitation was in the form of freezing rain and ice pellets. The front gradually extended toward Atlantic Canada during the night of December 20–21, affecting extreme Southern Quebec and later the Maritimes. By mid-day on December 21, an upper-level low had developed in central Texas, and this began to draw moisture from the Gulf of Mexico. While moving to
December 2013 North American storm complex
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and western Arkansas, with warm air moving north from the Gulf of Mexico to the Mississippi Valley. Conditions in Alabama and Mississippi were mostly cloudy with early thunderstorm activity, yet temperatures were already in the low 70s and upper 60s°F in Mississippi and western Tennessee. By afternoon, temperatures rose to the middle to upper 70s°F across most of the area. As a cold front approached Alabama, forecasters predicted afternoon thunderstorms and an end to the warm temperatures but did not anticipate the magnitude of the severe weather that later hit most of the state from north of Montgomery to the
1932 Deep South tornado outbreak
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City was able to reopen North Dubuque Street on Sunday, June 16. During the week starting September 9, a slow moving cold front stalled over Colorado, clashing with warm humid monsoonal air from the south. This resulted in rain and flooding along Colorado's Front Range from Colorado Springs north to Fort Collins. The situation intensified on September 11 and 12. Worst hit was Boulder County, with up to 21 inches of rain recorded. At least 6 deaths along the Front Range have been attributed to the flooding, and evacuations took place in many low-lying areas. The town of Lyons in
Floods in the United States: 2001–present
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absorbent open water (i.e., the albedo of this region has decreased). As a result, the region has heated up faster than other parts of the globe. With the lack of a sufficient temperature difference between Arctic and southern regions to drive jet stream winds, the jet stream may have become weaker and more variable in its course, allowing cold air usually confined to the poles to reach further into the mid latitudes. This jet stream instability brings warm air north as well as cold air south. The patch of unusual cold over the eastern United States was matched by anomalies
Early 2014 North American cold wave
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wraps around the northwest (southwest in the Southern Hemisphere) side of the cyclone, which can contain moderate to heavy precipitation. If the air mass is cold enough, the precipitation falls in the form of heavy snow. Theory from the 1980s talked about the presence of a cold conveyor belt originating north of the warm front and flowing along a clockwise path (in the northern hemisphere) into the main belt of the westerlies aloft, but there has been conflicting evidence as to whether or not this phenomenon actually exists. Inflow (meteorology) Inflow is the flow of a fluid into a large
Inflow (meteorology)
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precipitation and extremes of hot and cold. Summers can be very humid, with moist air riding up from the Gulf of Mexico, and during July and August daytime highs can reach into the triple digits. Winters vary from mild days to bitterly cold, with lows reaching into the teens below zero a few times a year. Neosho is situated in "Tornado Alley", a broad region where cold air from the Rocky Mountains and Canada collides with warm air from the Gulf of Mexico, leading to the formation of powerful storms. Neosho has had many severe outbreaks of tornadoes, including an
Neosho, Missouri
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people. Twenty-six of those deaths were caused by a single supercell thunderstorm which produced damaging and long lived tornadoes from north central Arkansas into northwest Tennessee. The outbreak was caused by a cold front that tracked across the central United States, triggered by a deep low pressure area in the Upper Midwest. The warm humid air mass ahead of the cold front, along with high upper-level wind shear, produced supercells across the region. The outbreak was expected to have started the previous day in the High Plains as the cold front tracked across that region. The supercells didn't really fire
Tornado outbreak of April 2, 2006
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Within a mid-latitude cyclone, these two key features play an essential role in frontogenesis. On the west side of a typical mid-latitude cyclone, there are northerly winds (associated with cold air) and east of the cyclone, southerly winds (associated with warm air); resulting in horizontal shear deformation. In the end, this results to concentrate a cyclonic shear along a line of maximum shear (which in this case is the birth of a cold front). On the eastern side of a cyclone, horizontal deformation is seen which turns into confluence (a result of translation + deformation). Horizontal deformation at low levels
Frontogenesis
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vortex, jet stream, and polar front equatorward. The jet stream is seen to "buckle" and deviate south. This rapidly brings cold dry air into contact with the warm, moist air of the mid latitudes, resulting in a rapid and dramatic change of weather known as a "cold snap". Ozone depletion occurs within the polar vortices – particularly over the Southern Hemisphere – reaching a maximum depletion in the spring. The polar vortex was first described as early as 1853. The phenomenon's sudden stratospheric warming (SSW) develops during the winter in the Northern Hemisphere and was discovered in 1952 with radiosonde
Polar vortex
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conditions commonly occur at the leading edge of a warm front. Because humidity is low at such high altitudes, this genus-type tends to be very thin. Cirrus clouds are composed of ice crystals that originate from the freezing of super cooled water droplets in regions where air temperature is lower than -20 °C or -30 °C.Cirrus usually occur in fair weather. They are formed when it is high enough to be cold and freeze the water drops into ice. They sometimes may be caused by turbulence and wind shear, or by upper-tropospheric convection. Sometimes they are like blown out ice-crystals
Cirrus cloud
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Warning from the NWS Cleveland Field Office for snow and freezing rain. On Monday night 3-6 inches of snow fell during the pre-frontal warm front. During the overnight hours of February 1–2, as the center of low pressure moved from Missouri to lower Indiana, it carried a warm front, with warm air advection and a shallow cold air pool at the bottom. This led to freezing rain in parts of Northeast Ohio. In Canton ice accretion ranged from 0.5 to 0.75 inch, which led to power lines and trees crashing, leaving almost 40,000 people without power. In the Greater Cleveland
January 31 – February 2, 2011 North American blizzard
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slows the wave front a little more than does the rare upper air, imparting a downward curve to the wave travel. Ducting can occur on a very large scale when a large mass of cold air is overrun by warm air. This is termed a temperature inversion, and the boundary between the two air masses may extend for or more along a stationary weather front. Temperature inversions occur most frequently along coastal areas bordering large bodies of water. This is the result of natural onshore movement of cool, humid air shortly after sunset when the ground air cools more quickly
Tropospheric propagation
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There were also hundreds of vehicle accidents related to the storm. After affecting Florida, the depression continued to the northeast, and although it had a warm core, it was not able to develop significantly due to lack of temperature instability, as well as another low developing southwest of the circulation. The depression was briefly forecast to strike North Carolina, but instead an eastward moving ridge kept it offshore. In Hatteras, North Carolina, the depression dropped of rainfall. The influx of cold air transitioned the depression to an extratropical cyclone on May 28. An approaching cold front absorbed the depression and
1958 Atlantic hurricane season
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for Florida, with damages of $218 million. In east central Florida, a warm sector, a region of warm surface air between a cold front and a warm front, was positioned ahead of a progressing cold front. Large scale lift was supported by a very strong jet stream aloft, with strong vertical shear evident, conducive for rotating thunderstorms and tornadoes. Instability increased overnight with temperatures and dew points increasing through the pre-dawn hours. For example, northwest of Orlando, temperatures were still at , which was about 3 degrees warmer than the average high for the day and 14 degrees warmer than
2007 Groundhog Day tornado outbreak