where can thunderstorm associated wind shear be found
Atmospheric convection


the instability and relative wind conditions at different layers of the atmosphere ("wind shear"). Single-cell thunderstorms form in environments of low vertical wind shear and last only 20–30 minutes. Organized thunderstorms and thunderstorm clusters/lines can have longer life cycles as they form in environments of significant vertical wind shear, which aids the development of stronger updrafts as well as various forms of severe weather. The supercell is the strongest of the thunderstorms, most commonly associated with large hail, high winds, and tornado formation. The
14916958
Mesoscale convective system


wind conditions at different layers of the atmosphere ("wind shear"). Single-cell thunderstorms form in environments of low vertical wind shear and last only 20–30 minutes. Organized thunderstorms and thunderstorm clusters/lines can have longer life cycles as they form in environments of sufficient moisture, significant vertical wind shear (normally greater than in the lowest of the troposphere)), which aids the development of stronger updrafts as well as various forms of severe weather. The supercell is the strongest of the thunderstorms, most commonly associated with
7963577
Thunderstorm


shear and last only 20–30 minutes. Organized thunderstorms and thunderstorm clusters/lines can have longer life cycles as they form in environments of significant vertical wind shear, normally greater than in the lowest of the troposphere, which aids the development of stronger updrafts as well as various forms of severe weather. The supercell is the strongest of the thunderstorms, most commonly associated with large hail, high winds, and tornado formation. Precipitable water values of greater than favor the development of organized thunderstorm complexes. Those with heavy rainfall normally have precipitable
20817319
Wind shear


microburst wind shear (headwind loss in excess of ). The rationale for this additional caution includes: Wind shear is also a key factor in the creation of severe thunderstorms. The additional hazard of turbulence is often associated with wind shear. Weather situations where shear is observed include: Weather fronts are boundaries between two masses of air of different densities, or different temperature and moisture properties, which normally are convergence zones in the wind field and are the principal cause of significant weather. Within surface weather analyses, they are depicted using
5641294
Multicellular thunderstorm


the thunderstorm sometimes not following the path of the cells that compose it. The typical hodograph, plot of the wind versus altitude, associated with it shows a linear wind shear with altitude The moderate vertical wind shear leads to the development of a non-symmetric surface convergence associated with the thunderstorm outflow, with the strongest convergence taking place on the downwind side from the storm's motion. So individual while cells moves along the windshear while the line moves at 30° of it, and 70% of the mean wind speed in
16112807
Wind shear


is stronger wind shear, this means that the storms become more slanted and the latent heat release is dispersed over a much larger area. Severe thunderstorms, which can spawn tornadoes and hailstorms, require wind shear to organize the storm in such a way as to maintain the thunderstorm for a longer period of time. This occurs as the storm's inflow becomes separated from its rain-cooled outflow. An increasing nocturnal, or overnight, low level jet can increase the severe weather potential by increasing the vertical wind shear through the troposphere
5641301
Hook echo


. J.R. Fulks developed the first hypothesis on the formation of hook echoes in 1962. Fulks analyzed wind velocity data from Doppler weather radar units which were installed in Central Oklahoma in 1960. Doppler data on wind velocity during thunderstorms demonstrated an association between strong horizontal wind shear and mesocyclones -strong thunderstorms with the potential to produce tornadoes; found in supercell thunderstorms - . Hook echoes are a reflection of the movement of air inside and around a supercell thunderstorm. Ahead of the base of the storm, the inflow from the environment is sucked in
12490904
Wind shear


level when walking across a plaza towards a tower block and suddenly encountering a strong wind stream that is flowing around the base of the tower. Sound movement through the atmosphere is affected by wind shear, which can bend the wave front, causing sounds to be heard where they normally would not, or vice versa. Strong vertical wind shear within the troposphere also inhibits tropical cyclone development, but helps to organize individual thunderstorms into longer life cycles which can then produce severe weather. The thermal wind concept explains how differences in wind speed
5641292
Outflow boundary


or less, distinguishing them as a type of downburst and apart from common wind shear which can encompass greater areas. They are normally associated with individual thunderstorms. Microburst soundings show the presence of mid-level dry air, which enhances evaporative cooling. Organized areas of thunderstorm activity reinforce pre-existing frontal zones, and can outrun cold fronts. This outrunning occurs within the westerlies in a pattern where the upper level jet splits into two streams. The resultant mesoscale convective system (MCS) forms at the point of the upper level
3028061
Air-mass thunderstorm


thunderstorm. Vertical wind shear is also a hazard near the base of thunderstorms which have generated outflow boundaries. The trigger for the lift of the initial cumulus cloud can be insolation heating the ground producing thermals, areas where two winds converge forcing air upwards, or where winds blow over terrain of increasing elevation. The moisture rapidly cools into liquid drops of water due to the cooler temperatures at high altitude, which appears as "cumulus" clouds. As the water vapor condenses into liquid, latent heat is released which warms the air
11928396
Wind


, and was a significant cause of aircraft accidents involving large loss of life within the United States. Sound movement through the atmosphere is affected by wind shear, which can bend the wave front, causing sounds to be heard where they normally would not, or vice versa. Strong vertical wind shear within the troposphere also inhibits tropical cyclone development, but helps to organize individual thunderstorms into living longer life cycles that can then produce severe weather. The thermal wind concept explains how differences in wind speed with height are dependent on horizontal temperature
14753315
Air-mass thunderstorm


An air-mass thunderstorm, also called an "ordinary", "single cell", or "garden variety" thunderstorm, is a thunderstorm that is generally weak and usually not severe. These storms form in environments where at least some amount of Convective Available Potential Energy (CAPE) is present, but very low levels of wind shear and helicity. The lifting source, which is a crucial factor in thunderstorm development, is usually the result of uneven heating of the surface, though they can be induced by weather fronts
11928393
Delta Air Lines Flight 191


to pilot error (for their decision to fly through a thunderstorm), combined with extreme weather phenomena associated with microburst-induced wind shear. The NTSB also determined that a lack of specific training, policies, and procedures for avoiding and escaping low-altitude wind shear was a contributing factor. The NTSB attributed the accident to lack of the ability to detect microbursts aboard aircraft – the radar equipment aboard aircraft at the time was unable to detect wind changes, only thunderstorms. After the investigation, NASA researchers at Langley Research Center
10707281
Thunderstorm


wind shear"), and they have separate downdrafts and updrafts (i.e., where its associated precipitation is not falling through the updraft) with a strong, rotating updraft (a "mesocyclone"). These storms normally have such powerful updrafts that the top of the supercell storm cloud (or anvil) can break through the troposphere and reach into the lower levels of the stratosphere. Supercell storms can be wide. Research has shown that at least 90 percent of supercells cause severe weather. These storms can produce destructive tornadoes,
20817326
Air-mass thunderstorm


can develop an outflow boundary which sets up new thunderstorm development. Such storms are rarely severe and are a result of local atmospheric instability; hence the term "air mass thunderstorm". When such storms have a brief period of severe weather associated with them, it is known as a pulse severe storm. Pulse severe storms are poorly organized due to the minimal vertical wind shear in the storm's environment and occur randomly in time and space, making them difficult to forecast. Between formation and dissipation, single cell thunderstorms normally last
11928399
Wind shear


. Thunderstorms in an atmosphere with virtually no vertical wind shear weaken as soon as they send out an outflow boundary in all directions, which then quickly cuts off its inflow of relatively warm, moist air and kills the thunderstorm. The atmospheric effect of surface friction with winds aloft force surface winds to slow and back counterclockwise near the surface of the Earth blowing inward across isobars (lines of equal pressure), when compared to the winds in frictionless flow well above the Earth's surface. This layer where friction slows and changes the
5641302
Thunderstorm


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 right angle to the wind shear direction. Thunderstorms result from the rapid upward movement of warm, moist air
20817305
Wind shear


glider pilots on rare occasions. Wind shear can also create wave. This occurs when an atmospheric inversion separates two layers with a marked difference in wind direction. If the wind encounters distortions in the inversion layer caused by thermals coming up from below, it will create significant shear waves that can be used for soaring. Strong outflow from thunderstorms causes rapid changes in the three-dimensional wind velocity just above ground level. Initially, this outflow causes a headwind that increases airspeed, which normally causes a pilot to reduce engine power if
5641308
Wind shear


various colored lines and symbols. The air masses usually differ in temperature and may also differ in humidity. Wind shear in the horizontal occurs near these boundaries. Cold fronts feature narrow bands of thunderstorms and severe weather, and may be preceded by squall lines and dry lines. Cold fronts are sharper surface boundaries with more significant horizontal wind shear than warm fronts. When a front becomes stationary, it can degenerate into a line which separates regions of differing wind speed, known as a shear line, though the wind direction across the
5641295
Thunderstorm


the ground by the downdraft cuts off the inflow of the thunderstorm, the updraft disappears and the thunderstorm will dissipate. Thunderstorms in an atmosphere with virtually no vertical wind shear weaken as soon as they send out an outflow boundary in all directions, which then quickly cuts off its inflow of relatively warm, moist air, and kills the thunderstorm's further growth. The downdraft hitting the ground creates an outflow boundary. This can cause downbursts, a potential hazardous condition for aircraft to fly through, as a substantial change in wind speed
20817317
Mesocyclone


within strong thunderstorms. Thunderstorms containing persistent mesocyclones are supercell thunderstorms. Mesocyclones occur on the "mesoscale" from a few kilometers to hundreds of kilometers. Doppler radar is used to identify mesocyclones. A mesovortex is a similar but typically smaller and weaker rotational feature associated with squall lines. Mesocyclones form when strong changes of wind speed and/or direction with height ("wind shear") sets parts of the lower part of the atmosphere spinning in invisible tube-like rolls. The convective updraft of a thunderstorm then draw up this spinning air
11858701
Wind


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, weather fronts, areas of locally higher low level winds referred to as low level jets, near mountains, radiation inversions that occur because of clear skies and calm winds, buildings, wind turbines, and sailboats. Wind shear has a significant effect on the control of aircraft during take-off and landing
14753314
Thunderstorm


and direction occurs, resulting in a decrease of airspeed and the subsequent reduction in lift for the aircraft. The stronger the outflow boundary is, the stronger the resultant vertical wind shear becomes. There are four main types of thunderstorms: single-cell, multi-cell, squall line (also called multi-cell line) and supercell. Which type forms depends on the instability and relative wind conditions at different layers of the atmosphere ("wind shear"). Single-cell thunderstorms form in environments of low vertical wind
20817318
Thunderstorm


large hailstones, and flash flooding caused by heavy precipitation. Stronger thunderstorm cells are capable of producing tornadoes and waterspouts. There are four types of thunderstorms: single-cell, multi-cell cluster, multi-cell lines and supercells. Supercell thunderstorms are the strongest and most severe. Mesoscale convective systems formed by favorable vertical wind shear within the tropics and subtropics can be responsible for the development of hurricanes. Dry thunderstorms, with no precipitation, can cause the outbreak of wildfires from the heat generated from the cloud-to-
20817308
Gustnado


more correctly describes the rare tornadic gustnado that connects the surface to the ambient clouded base, or more commonly to the relatively brief but true tornadoes that are associated with a mesovortex. The most common setting for a gustnado is along the gust front of a severe thunderstorm (by many definitions, containing wind speeds of at least ), along which horizontal shear of the wind may be large. A particularly common location is along the rear-flank gust front of supercell storms. Gustnadoes probably form owing to shear instability associated with the
17526138
Hurricane Noel


northeast of the northern Lesser Antilles. The system continued westward with disorganized convection, and was unable to develop further due to strong wind shear. Despite the shear, convection increased as barometric pressures dropped in association with the organizing system. Turning west-southwestward, the low passed over the United States Virgin Islands on October 25 and just southeast of Puerto Rico the next day. Decreasing wind shear on October 27 allowed the thunderstorms to increase over the center late on October 27. After further organization, the system developed into Tropical Depression
1684951
Outflow boundary


the boundary can cause thunderstorms to exhibit rotation at the base of the storm, at times causing tornadic activity. Strong versions of these features known as downbursts can be generated in environments of vertical wind shear and mid-level dry air. Microbursts have a diameter of influence less than , while macrobursts occur over a diameter greater than . Wet microbursts occur in atmospheres where the low levels are saturated, while dry microbursts occur in drier atmospheres from high-based thunderstorms. When an outflow boundary moves into a more stable low level environment
3028058
Cyclogenesis


-laden environments with little vertical wind shear along lines of convergence, such as land breezes, lines of frictional convergence from nearby landmasses, or surface troughs. Their parent cloud can be as innocuous as a moderate cumulus, or as significant as a thunderstorm. Waterspouts normally develop as their parent clouds are in the process of development, and it is theorized that they spin up as they move up the surface boundary from the horizontal wind shear near the surface, and then stretch upwards to the cloud once the low level shear vortex
14998909
Cyclogenesis


of the troposphere, enough Coriolis force to develop a low pressure center, a pre-existing low level focus or disturbance, and low vertical wind shear. These warm core cyclones tend to form over the oceans between 10 and 30 degrees of the equator. Mesocyclones range in size from mesoscale beta to microscale. The term mesocyclone is usually reserved for mid-level rotations within severe thunderstorms, and are warm core cyclones driven by latent heat of its associated thunderstorm activity. Tornadoes form in the warm sector of extratropical cyclones where a
14998904
Thunderstorm


it, and this cold air spreads out at the Earth's surface, occasionally causing strong winds that are commonly associated with thunderstorms. Thunderstorms can form and develop in any geographic location but most frequently within the mid-latitude, where warm, moist air from tropical latitudes collides with cooler air from polar latitudes. Thunderstorms are responsible for the development and formation of many severe weather phenomena. Thunderstorms, and the phenomena that occur along with them, pose great hazards. Damage that results from thunderstorms is mainly inflicted by downburst winds,
20817307
Derecho


and August in the Northern Hemisphere, within areas of moderately strong instability and moderately strong vertical wind shear. However, derechos may occur at any time of the year, and can occur as frequently at night as during the day. Various studies since the 1980s have shed light on the physical processes responsible for the production of widespread damaging winds by thunderstorms. In addition, it has become apparent that the most damaging derechos are associated with particular types of mesoscale convective systems that are self-perpetuating (meaning that the convective systems are
16581983
2002–03 South Pacific cyclone season


November 29 from a broad area of thunderstorms embedded within a monsoonal trough, originating from a westerly wind burst associated with El Niño conditions; the same area of disturbed weather would later generate Typhoon Pongsona on December 2. At the time, the tropical depression was moving towards the southeast, but strong wind shear displaced the cyclone's strongest winds and convection northeast of its circulation center. Convective activity fluctuated under strong diurnal temperature variation. After moving into an area of less wind shear, the system was able to organize and develop good
15063939
Outflow boundary


of intersection with another boundary (cold front, dry line, another outflow boundary, etc.). Outflow boundaries can be seen either as fine lines on weather radar imagery or else as arcs of low clouds on weather satellite imagery. From the ground, outflow boundaries can be co-located with the appearance of roll clouds and shelf clouds. Outflow boundaries create low-level wind shear which can be hazardous during aircraft takeoffs and landings. If a thunderstorm runs into an outflow boundary, the low-level wind shear from
3028057
Squall line


shear is an important aspect of a squall line. In low to medium shear environments, mature thunderstorms will contribute modest amounts of downdrafts, enough to help create a leading edge lifting mechanism – the gust front. In high shear environments created by opposing low level jet winds and synoptic winds, updrafts and consequential downdrafts can be much more intense (common in supercell mesocyclones). The cold air outflow leaves the trailing area of the squall line to the mid-level jet, which aids in downdraft processes. Severe squall lines typically
7065422
Hurricane Rafael


upper-level trough and the cyclone itself. Moderate to strong wind shear dislocated the center of Rafael and the deepest shower and thunderstorm activity. Over the course of the next few days, however, the upper-level trough gradually weakened and backed westward, allowing for the development of an anticyclone atop the tropical storm. Wind shear lessened, allowing the center to become obscured from view and outflow to develop in association with the system. As it began to execute a turn towards the north under the influence of an upper-
5581225
Thunderstorm


Earth's troposphere, the lowest of the Earth's atmosphere. Weaker thunderstorms are steered by winds closer to the Earth's surface than stronger thunderstorms, as the weaker thunderstorms are not as tall. Organized, long-lived thunderstorm cells and complexes move at a right angle to the direction of the vertical wind shear vector. If the gust front, or leading edge of the outflow boundary, races ahead of the thunderstorm, its motion will accelerate in tandem. This is more of a factor with thunderstorms with heavy precipitation (HP
20817332
Squall


within the leading space of an advancing cold front. Pressure perturbations within an extent of a thunderstorm are noteworthy. With buoyancy rapid within the lower and mid-levels of a mature thunderstorm, one might believe that low pressure dominates in the mesoscale environment. However, this is not the case. With downdrafts ushering colder air from mid-levels, hitting ground and propagating away in all directions, high pressure is to be found widely at surface levels, usually indicative of strong (potentially damaging) winds. Wind shear is an
11858782
Upper tropospheric cyclonic vortex


a rapid development of active thunderstorm activity. Cloud bands associated with upper tropospheric cyclonic vortices are aligned with the vertical wind shear. Animated satellite cloud imagery is a better tool for their early detection and tracking. The low-level convergence caused by the cut-off low can trigger squall lines and rough seas, and the low-level spiral cloud bands caused by the upper level circulation are parallel to the low-level wind direction. This has also been witnessed with upper level lows which occur at higher latitudes. For example
15535082
Wind shear


Wind shear (or windshear), sometimes referred to as wind gradient, is a difference in wind speed 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 change in altitude. Horizontal wind shear is a change in wind speed with 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
5641290
Tropical Depression Two-E (2006)


area not favorable for significant strengthening, due to land interaction and wind shear. It was tracking steadily northeastward, and as it moved closer to the coastline, the center of the depression was difficult to locate. However, the overall organization briefly improved, and in one forecast the depression was predicted to attain tropical storm status. Early on June 4, convection weakened significantly, leaving the center partially exposed. Continued wind shear brought most of the associated thunderstorm activity onshore southwestern Mexico while the center of the depression remained just offshore.
11833683
1981 Pacific typhoon season


center has formed in association with the thunderstorm complex, which was moving northwest. Ship reports indicated the system had become a tropical storm by the morning of July 18. Southwesterly vertical wind shear impacted Maury, which led to its tilting to the northeast with height. By early on July 19 the wind shear lessened, and the cyclone's structure improved. While approaching China, a strong ridge to its northwest deflected the storm on a more westerly heading, sending the center toward Taiwan. This ridge also led to weak east-
3390915
Typhoon June (1984)


the monsoon trough. A large area of convection was first detected on satellite imagery, and at midday, the Joint Typhoon Warning Center determined that a closed area of low pressure developed between the 135th meridian east and the 140th meridian east. The associated thunderstorm activity initially failed to consolidate due to strong wind shear caused by a displaced anticyclone. The Japan Meteorological Agency (JMA) started to track the system 06:00 UTC on August 26. The next day, the wind shear began to relent, as an upper-level anticyclone became
6443013
Intertropical Convergence Zone


the formation of tropical cyclones within this zone more possible. Surges of higher pressure from high latitudes can enhance tropical disturbances along its axis. In the north Atlantic and the northeastern Pacific oceans, tropical waves move along the axis of the ITCZ causing an increase in thunderstorm activity, and clusters of thunderstorms can develop under weak vertical wind shear. Thunderstorms along the Intertropical Convergence Zone played a role in the loss of Air France Flight 447, which left Rio de Janeiro–Galeão International Airport on Sunday, May 31, 2009, at
3362194
Hurricane Beryl


trough, thunderstorms developed and persisted near the storm's center, with gale-force winds detected east of the center; after continued reorganization, Beryl was re-designated as a subtropical storm at 17:00 UTC that day, while located well off the East Coast of the United States. However, the rejuvenated storm soon began to weaken as nearby dry air intruded and weakened showers and thunderstorms associated with the storm, and impinging northwesterly shear further served to remove thunderstorm activity. By July 15, Beryl consisted mostly of a low to
20491486
2009 Minnesota tornadoes


, leading to two tornadoes near Carlisle and Dent. During the late afternoon a very warm and humid air mass lifted northward across northern Iowa and into far southern Minnesota. Several weak storms formed in northwest and north central Iowa and moved into south central Minnesota where a warm front laid. Winds shifted from the south to the east and southeast across Freeborn and Faribault counties of far south central Minnesota. The combination of increasing wind shear near the boundary layer and enough lift from thunderstorms allowed brief tornadoes to develop. Thunderstorms produced damaging winds
8501230
Wind shear


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 control of an aircraft, and it has been a sole or contributing cause of many aircraft accidents. Wind shear is sometimes experienced by pedestrians at ground
5641291
Squall


important aspect to measuring the potential of squall line severity and duration. In low to medium shear environments, mature thunderstorms will contribute modest amounts of downdrafts, enough to turn will aid in create a leading edge lifting mechanism – the gust front. In high shear environments created by opposing low level jet winds and synoptic winds, updrafts and consequential downdrafts can be much more intense (common in supercell mesocyclones). The cold air outflow leaves the trailing area of the squall line to the mid-level jet, which aids in downdraft
11858783
2010–11 South-West Indian Ocean cyclone season


in wind shear and an increase in convection over the center. Persistent wind shear prevented the system from organizing, causing the thunderstorms to be removed from the center. The JTWC discontinued advisories on the cyclone on 27 October, and on the same day the MFR downgraded it to a tropical disturbance. On 29 October, the MFR issued their final advisory on the system. The remnants continued to the west-southwest, occasionally producing thunderstorms through early November. On 23 November, an area of convection persisted southwest of Sumatra within the
4557852
Subtropical Storm Andrea (2007)


the east of the cyclone within a band of moderate convection due to a brief spell of westerly vertical wind shear. The center of circulation had become disorganized, with several small cloud swirls within the larger circulation. This disorganization of the center, combined with increasing wind shear and dry air suppressing convective activity, caused it to begin weakening later that morning. By 1500 UTC on May 10, only a few thunderstorms remained near the center, and thus the NHC downgraded Andrea to subtropical depression status. Though a few intermittent thunderstorms persisted
10591791
Wind shear


sail design, but this can be difficult to predict since wind shear may vary widely in different weather conditions. Sailors may also adjust the trim of the sail to account for low level wind shear, for example using a boom vang. Wind shear can have a pronounced effect upon sound propagation in the lower atmosphere, where waves can be "bent" by refraction phenomenon. The audibility of sounds from distant sources, such as thunder or gunshots, is very dependent on the amount of shear. The result of these differing sound
5641312
Anticyclonic tornado


cyclonically. Rotation in these synoptic scale systems stems partly from the Coriolis effect, but thunderstorms and tornadoes are too small to be significantly affected. The common property here is an area of lower pressure, thus surrounding air flows into the area of less dense air forming cyclonic rotation. The rotation of the thunderstorm itself is induced mostly by vertical wind shear, specifically clockwise turning as altitude increases (called a veered vertical profile, although backed profiles can occur with anticyclonic supercells]]. Various processes can produce an anticyclonic tornado. Most
15871576
Cold front


spread a considerable distance downwind from the thunderstorms. The other cloud types associated with a cold front depend on atmospheric conditions such as air mass stability and wind shear. As the front approaches, middle-étage gives way to altostratus and low-level stratocumulus with intermittent light precipitation if the warm airmass being displaced by the cold front is mostly stable. With significant airmass instability, vertically developed cumulus or cumulonimbus with showers and thunderstorms will form along the front. After the passage of the cold front, the sky usually clears as high
7604777
Bow echo


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. 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 life span of 3 to 6 hours. Bow echoes tend to develop when moderate to strong wind shear exists in the lower 2 to 3 km of the atmosphere
7452613
2009 Pacific hurricane season


and thunderstorm activity associated with the system gradually increased over the next several days as it tracked west-northwestward. By July 15, the low became sufficiently organized and was declared a tropical depression roughly of Manzanillo, Colima. Turning towards the northwest in response to a ridge over Mexico, the depression intensified into Tropical Storm Dolores later that day. Despite southwesterly wind shear displacing the center of Dolores from the deepest convection, the system continued to strengthen, attaining peak winds of on July 16. Shortly thereafter, convection associated with the
9723064
Thunderstorm


. Severe weather in the form of strong straight-line winds can be expected in areas where the squall line itself is in the shape of a bow echo, within the portion of the line that bows out the most. Tornadoes can be found along waves within a line echo wave pattern, or LEWP, where mesoscale low pressure areas are present. Some bow echoes in the summer are called derechos, and move quite fast through large sections of territory. On the back edge of the rain shield associated with mature squall lines
20817324
Surface weather analysis


half-circles and blue spikes pointing in opposite directions, indicating no significant movement. When stationary fronts become smaller in scale, degenerating to a narrow zone where wind direction changes over a short distance, they become known as shear lines. If the shear line becomes active with thunderstorms, it may support formation of a tropical storm or a regeneration of the feature back into a stationary front. A shear line is depicted as a line of red dots and dashes. Mesoscale features are smaller than synoptic scale systems like fronts, but
21616176
Tornado outbreak of February 10–11, 2009


throughout the afternoon across Oklahoma and Texas as cloud cover shifted eastward. Cooling aloft, in conjunction with the approaching storm system, led to atmospheric instability, resulting in thunderstorms. A very strong wind field increased with height through the lower troposphere, resulting in a wind shear favorable for rotation in the thunderstorms. Meteorologists expected large hail stones and damaging winds, and recognized the potential for strong tornadoes as thunderstorms developed from central Oklahoma southward into north-central Texas in the afternoon. During the night, a cold front moved eastward toward
11953824
Thunderstorm


are still present, the falling rain drags the surrounding air with it, creating "downdrafts" as well. The simultaneous presence of both an updraft and a downdraft marks the mature stage of the storm and produces cumulonimbus clouds. During this stage, considerable internal turbulence can occur, which manifests as strong winds, severe lightning, and even tornadoes. Typically, if there is little wind shear, the storm will rapidly enter the dissipating stage and 'rain itself out', but, if there is sufficient change in wind speed
20817315
Hurricane Odile


"Odile". Further intensification was slowed because of strong wind shear, which caused the storm's center of circulation to be displaced from the bulk of convection. Due to the lack of atmospheric steering currents at the time, Odile assumed a slow, meandering course towards the west. Continued wind shear caused the tropical storm to become disorganized on September 11 before abating on September 12, allowing for thunderstorms to rebuild over Odile's circulation center. The relaxed wind shear enabled the growth of intense rainbands encircling the tropical cyclone as well
16652103
Tornado outbreak sequence of May 2003


it to rise; high CAPE values are usually associated with severe weather. CAPE values during the period of April 30–May 11 were extremely high in the affected areas. A strong, persistent southeast to northwest upper level flow contributed to wind shear, and induced strong rotation in many of the thunderstorms that developed. These rotating thunderstorms, or supercells, are capable of spawning tornadoes. The meteorological ingredients that made conditions favorable for devastating severe weather came together early in the day on May 4. One of the 500 mb shortwaves that had
15698367
Vertical draft


, and is the central source of thunderstorms. Drafts can also be conceived 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 a downdraft. Updrafts and downdrafts, along with wind shear in general, are a major contributor to airplane crashes during takeoff and landing in a thunderstorm. Extreme cases
20698001
Severe weather


into severe weather. For example, a pool of cold air aloft may aid in the development of large hail from an otherwise innocuous appearing thunderstorm. However, the most severe hail and tornadoes are produced by supercell thunderstorms, and the worst downbursts and derechos (straight-line winds) are produced by bow echoes. Both of these types of storms tend to form in environments high in wind shear. Floods, hurricanes, tornadoes, and thunderstorms are considered to be the most destructive weather-related [develop models to predict the
6097957
Severe weather


rain-cooled air in their formation. Derechos are longer, usually stronger, forms of downburst winds characterized by straight-lined windstorms. Downbursts create vertical wind shear or microbursts, which are dangerous to aviation. These convective downbursts can produce damaging winds, lasting 5 to 30 minutes, with wind speeds as high as , and cause tornado-like damage on the ground. Downbursts also occur much more frequently than tornadoes, with ten downburst damage reports for every one tornado. A squall line is an elongated line of severe thunderstorms
6097967
Aviation safety


giving false readings. A wind shear is a change in wind speed and/or direction over a relatively short distance in the atmosphere. A microburst is a localized column of sinking air that drops down in a thunderstorm. Both of these are potential weather threats that may cause an aviation accident. Strong outflow from thunderstorms causes rapid changes in the three-dimensional wind velocity just above ground level. Initially, this outflow causes a headwind that increases airspeed, which normally causes a pilot to reduce engine power if they are unaware of the wind
11312794
Monsoon trough


normally as shear lines when their temperature gradient becomes minimal, wind surges can cross the equator in oceanic regions and enhance a monsoon trough in the other hemisphere's summer. A key way of detecting whether a wind surge has reached a monsoon trough is the formation of a burst of thunderstorms within the monsoon trough. If a circulation forms within the monsoon trough, it is able to compete with the neighboring thermal low over the continent, and a wind surge will occur at its periphery. Such a circulation which is broad in nature
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Tornado


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 "rolling" effect (often exemplified through a roll cloud). If low level wind shear is strong enough, the rotation can be turned vertically or diagonally and make contact with the ground. The result is a gustnado. They usually cause small areas of heavier rotational wind damage among areas of straight-line wind damage
16803856
2000–01 South-West Indian Ocean cyclone season


. Associated convection, or thunderstorms, gradually organized into a central dense overcast, and the system became Tropical Disturbance 3 at 06:00 UTC on December 31. The upper-level environment generally favored further development, but the system failed to develop more initially due to some easterly wind shear. A large ridge to the south steered the nascent disturbance to the west-southwest. After the shear subsided, the system intensified into a moderate tropical storm on January 2, given the name "Ando" by the Mauritius Meteorological Service. Also
15567067
2010 Bronx tornado


prompted the SPC to issue a severe thunderstorm watch for all of southern Pennsylvania, the entire state of New Jersey and parts of northern West Virginia, Maryland, Delaware and Virginia. Around the time the watch was issued, wind shear values began to decrease over the region; however, moderately strong winds persisted over a large area, fueling further development of thunderstorms. Ahead of these storms, surface heating from days of above-average temperatures (exceeding ) and a moist air mass provided significant instability, another factor favoring thunderstorm formation
5906570
2004 Myanmar cyclone


developing good outflow despite the presence of wind shear. As the shear decreased, the thunderstorms increased and organized, with the eastward-moving circulation partially exposed. At 09:00 UTC on May 16, the India Meteorological Department classified the system as a depression, and nine hours later the agency upgraded it to a deep depression as the system turned northwestward. The nascent system quickly organized, aided by the decreasing wind shear, as well as a surge in the monsoon. The IMD upgraded the depression to a cyclonic storm at 03:00 UTC
19116370
Extratropical cyclone


path at a moderate rate of progress. During fall, winter, and spring, the atmosphere over continents can be cold enough through the depth of the troposphere to cause snowfall. Squall lines, or solid bands of strong thunderstorms, can form ahead of cold fronts and lee troughs due to the presence of significant atmospheric moisture and strong upper level divergence, leading to hail and high winds. When significant directional wind shear exists in the atmosphere ahead of a cold front in the presence of a strong upper level jet stream, tornado
4137825
Tropical Depression Ten (2005)


Upon its designation, the depression consisted of a large area of thunderstorm activity, with curved banding features and expanding outflow. The environmental conditions were predicted to quickly become unfavorable, however. The depression moved erratically and slowly towards the west, and wind shear inhibited any significant intensification. Late on August 13, it was "beginning to look like Irene-junior as it undergoes southwesterly mid-level shear beneath the otherwise favorable upper-level outflow pattern". The wind shear was expected to relent within 48 hours, prompting some
5099847
1999–2000 South-West Indian Ocean cyclone season


, displaced due to wind shear, but organized enough for the MFR to track it as Tropical Disturbance 8. The shear gradually decreased, allowing the thunderstorms to organize as it moved westward. On February 28, the JTWC classified the system as Tropical Cyclone 15S, and on February 29 the MFR upgraded it to tropical depression status. The depression turned west-northwestward before rounding a ridge and turning to the southwest. The thunderstorms organized into a central dense overcast on March 1, prompting the MFR to upgrade it to Moderate Tropical
239569
Tri-State Tornado


also in place just above the surface as winds veered with height, resulting in low-level curvature and long hodographs. Strong wind shear thus existed, with pronounced directional shear likely in the vicinity of the warm front, with winds at the 700 hPa height level west-southwesterly around and winds about at 500 hPa. Theoretical hodographs returned estimated storm relative environmental helicity (SREH) values of 340 m s in the vicinity of the Tri-State supercell track. Strong thunderstorms were now scattered throughout the warm sector and a line
15647886
Tropical Storm Debby (1994)


USD). On nearby Dominica, Debby damaged crops and fisheries. While Debby was crossing Saint Lucia, its strongest thunderstorms were located north and east of the center due to wind shear. A station in Martinique reported hurricane-force winds, and about 20,000 people on the island lost power. After entering the eastern Caribbean Sea, Debby attained peak winds of , although continued wind shear caused the storm to dissipate on September 11. In Puerto Rico, one person died due to high waves. The storm caused power outages and
18865394
Eastern Air Lines Flight 66


recorded by the cockpit voice recorder, the captain of Flight 66 was aware of reports of severe wind shear on the final approach path (which he confirmed by radio to the final-vector controller), but decided to continue nonetheless. The NTSB published its final report on March 12, 1976, determining the following probable cause of the accident: The National Transportation Safety Board determines that the probable cause of this accident was the aircraft's encounter with adverse winds associated with a very strong thunderstorm located astride the ILS localizer course,
14031322
Cyclone Dina


flooding destroyed many homes, washed out roads, and caused catastrophic agricultural damage. Destructive winds, measured up to also crippled communications. In all, six people died on the island and losses were estimated at €200 million (US$190 million). On January 15, a tropical disturbance began organizing near the Chagos Archipelago in the South Indian Ocean convergence zone, which is an extended area of convection connected to the monsoon. The thunderstorms gradually organized, associated with a weak circulation and located within an area of moderate wind shear
15458309
1997 Atlantic hurricane season


moved northeastward, passing southeast of the Outer Banks. Despite the presence of wind shear it developed banding features. On July 14, the storm reached peak winds of . Thereafter, Claudette turned eastward ahead of a frontal system. Its associated thunderstorm activity was sporadic and relatively disorganized, and the storm weakened to a tropical depression on July 16. Claudette briefly re-intensified into a tropical storm before becoming extratropical later that day. Shortly thereafter, it merged with a cold front, while the remnants were last noted near the Azores
19537579
Tropical Storm Bonnie (2010)


winds; it is estimated the cyclone lost tropical storm status around 1800 UTC that same day. On the morning of July 24, deep convection briefly redeveloped over the center as Bonnie emerged into the Gulf of Mexico. Despite the redevelopment, the storm subsequently entered a region of intense upper-level winds, causing associated convection to become sheared away rapidly. Embedded within a well-established steering flow, Bonnie further degenerated to a tight swirl of low clouds, with no more than a few remaining patches of strong thunderstorms. Subsequent
4645126
2011 Atlantic hurricane season


off the coast of Africa, associated with plentiful shower and thunderstorm activity. Moving westward and embedded within a favorable environment for development, the wave quickly became organized. On September 24, a tropical depression developed about 290 mi (465 km) south of the southernmost Cape Verde Islands. Later that day, the depression intensified into Tropical Storm Philippe. Strong wind shear from upper level winds and later on from Ophelia's outflow, as well as periodic entrainment of dry air, kept the cyclone both small and disorganized. Additionally,
6302455
Hurricane Earl (2016)


however, this feature was transient and soon dissipated. Moving quickly westward, the system was expected to encounter more favorable conditions for development within three days. The rapid motion prevented initial development, resulting in poor organization of the associated convection. The thunderstorms increased on July 30 as the wave began moving through the Lesser Antilles, assisted by above-normal water temperatures and light wind shear. Despite more convective organization and the presence of strong winds, the lack of a surface circulation prevented the system from being classified as a tropical cyclone
7206874
1996 Pacific hurricane season


, with a total of twenty-two people aboard, were missing. Their fate is unknown. The National Hurricane Center received no reports of damage due to Tropical Storm Cristina; however, there was flooding due to storm surge and damage from wind. It also produced rain. On July 4, a persistent area of thunderstorms organized into a tropical depression. Weak steering currents slowly moved it northwest. Easterly wind shear inhibited the development of the system. Despite the wind shear, Six-E was forecast to strengthen into a
16192359
Hurricane Nicole (2016)


with gale-force winds. Around the same time, thunderstorm activity became better organized and banding features began to evolve over the eastern side of the disturbance. As a result, the NHC classified the system as Tropical Storm "Nicole" at 15:00 UTC, while it was located about northeast of San Juan, Puerto Rico. The storm, still plagued by inhibiting wind shear, was forecast to remain weak. Nicole's cloud pattern gradually improved on October 5, partially shielded from the effects of wind shear by an upper-
17335164
Air-mass thunderstorm


, causing it to become less dense than the surrounding dry air. The air tends to rise in an "updraft" through the process of convection (hence the term convective precipitation). This creates a low-pressure zone beneath the forming thunderstorm, otherwise known as a cumulonimbus cloud. In a typical thunderstorm, approximately 5×10 kg of water vapor is lifted into the Earth's atmosphere. As they form in areas of minimal vertical wind shear, the thunderstorm's rainfall creates a moist and relatively cool outflow boundary with undercuts the
11928397
Air-mass thunderstorm


there could be a weak downburst and small hail. They are common in temperate zones during a summer afternoon. Like all thunderstorms, the mean-layered wind field the storms form within determine motion. When the deep-layered wind flow is light, outflow boundary progression will determine storm movement. Since thunderstorms can be a hazard to aviation, pilots are advised to fly above any haze layers within regions of better visibility and to avoid flying under the anvil of these thunderstorms, which can be regions where hail falls from the parent
11928395
2013 Somalia cyclone


-minute sustained winds of 75 km/h (45 mph). Continued moderate wind shear displaced most convection to the northwest of the center of circulation, counteracting the favorable poleward outflow which was enhanced by the mid-latitude westerlies. The wind shear took its toll by November 10, leaving the storm's center devoid of showers and thunderstorms. More pronounced decay took place later in the day as the storm neared the coastline, with land interaction disrupting the circulation. Between 2300 UTC on November 10 and 0000 UTC on November
11318937
Tropical Storm Gabrielle (2007)


increased northerly wind shear displaced the center of Gabrielle to the north of the thunderstorm activity. Based on reports from Hurricane Hunters, it is estimated Gabrielle moved ashore at Cape Lookout National Seashore at 1530 UTC on September 9 with winds of 60 mph (95 km/h), though due to the shear the strongest winds remained offshore. Tracking around the ridge over the western Atlantic, the storm turned to the north and north-northeast, emerging into the ocean near Kill Devil Hills, North Carolina early on September 10 as
6289810
Typhoon Goni (2015)


and flooded a zoo in eastern Russia. In the middle of August 2015, a strong westerly wind burst along the equator produced two areas of convection, or thunderstorm activity, near the Marshall Islands in the western Pacific Ocean. The westernmost disturbance became associated with a circulation center near Ujelang Atoll. With low wind shear and favorable sea surface temperatures, tropical cyclone forecast models anticipated further development of both convective systems. The westernmost system developed a banding pattern by August 13, indicative of increased organization. At 18:00 UTC that day,
14861116
Tropical Storm Danny (2009)


Africa on August 18. Convective activity associated with the system briefly began to organize on August 22, but wind shear soon halted further development. On August 24, thunderstorms once again increased as the disturbance interacted with an upper-level trough. On August 25, a Hurricane Hunters mission into the system revealed a broad area of tropical-storm force winds, but no closed circulation center. However, around 0900 UTC on August 26, satellite imagery and QuikSCAT data indicated that a closed low had formed. While situated about east
6927047
1981 Pacific typhoon season


a new upper level high formed to its east, inducing southerly vertical wind shear. Weakening began while the storm was located about east of Guam late on April 18. Moderate to heavy rainfall did occur on the island, with to being measured. After passing Guam, the remaining thunderstorm activity sheared away, leaving a low-level swirl which moved northwest. The cyclone was absorbed by a system approaching in the main belt in the Westerlies on April 19. A broad area of thunderstorm straddled the equator around the International Date Line
3390905
2001–02 South-West Indian Ocean cyclone season


wind shear in the region prevented significant strengthening. The convection slowly organized, and the depression intensified into Tropical Storm Ikala early on March 25. By that time, the shear had decreased, although initially it was strong enough to prevent the convection from covering the center. An approaching cold front turned the storm to the southeast on March 25, where upper-level conditions became more favorable for strengthening. Thunderstorms increased over the center, and an eye began developing on March 26. The next day, Ikala intensified into a tropical
15496613
Tropical Storm Kammuri (2002)


. An upper-level low connected to a trough weakened the ridge over China, allowing Kammuri to move slowly northward. Continued wind shear initially prevented the thunderstorms from being located over the center, although the shear gradually decreased, allowing the convection to organize. Kammuri quickly intensified into a severe tropical storm; the JMA estimated peak 10-minute sustained winds of 100 km/h (65 mph) at 1800 UTC on August 4. The JTWC estimated the storm was weaker, with 1-minute winds of 95 km/h (60 mph
41750
Tornado watch


sufficient to breed development of severe thunderstorms that are capable of producing significant tornadoes (either from supercells that develop strong, low-level rotation under typical tornadogenesis during the storm's maturation stage, or by thunderstorms that initiate mesocyclone maturation during their early development through a combination of sufficient wind shear and very high convective available potential energy (CAPE) values). Occasionally, a tornado watch may replace a severe thunderstorm watch (or a portion of one) should conditions that were originally forecast to be conducive for non-tornadic severe thunderstorms
1365384
2002–03 South-West Indian Ocean cyclone season


center of the thunderstorms, prompting MFR to upgrade the storm to peak winds of 130 km/h (80 mph). At that time, the storm was in an area of weak wind shear, although increasing shear caused rapid weakening and for the eye to dissipate. Early on April 12, Luma became extratropical as it merged with an approaching cold front. Late in the season in April, an area of convection formed southwest of Diego Garcia. It gradually organized, and there was a companion system to the west that
15063875
Meteorological history of Hurricane Andrew


, the storm maintained concentrated convection near the center with spiral bands to its west as the winds increased to . Shortly thereafter the thunderstorms decreased markedly during the diurnal minimum, and as the storm turned to the northwest increased southwesterly wind shear from an upper-level low prevented Andrew from maintaining deep convection. On August 19, a Hurricane Hunters flight into the storm failed to locate a well-defined center, and the next day a flight found that the cyclone had degenerated to the extent that only a diffuse low-level circulation
8070432
Tornado outbreak of January 21–23, 1999


/h) and 850mb winds topped 70 mph (110 km/h) across the High risk area. The combination of speed shear and adequate directional shear (noted by curved low-level hodographs) led to 0–3 km storm relative helicities of 300–500 m2/s2, favorable for rotating thunderstorms. A capping inversion, qualified by cold and dry air aloft, initially prevented the formation of thunderstorms and instead allowed substantial surface heating. Surface-based CAPE values of 1500–2000 j/kg and most unstable CAPE values of 1000–2000
18740141
Tornadoes of 2011


into the Northland from the Tasman Sea, bringing unsettled weather to much of the region. The Meteorological Service of New Zealand Limited (MetService) mentioned the possibility of strong thunderstorms being embedded within the line, producing small hail and gusty winds. Significant upward motion in the atmosphere developed in the region surrounding Auckland, prompting the MetService to issue a high-risk of thunderstorms in the area. With low-level wind shear and helicity, the possibility of tornadic activity was present. At 2:55 pm NZST, a hook echo was
18971180
Cyclone Leon–Eline


February 8, the circulation was exposed from the rapidly dwindling thunderstorms. At 18:00 UTC that day, Leon crossed 90° E into the south-west Indian Ocean, and as result was renamed Eline by the Mauritius Meteorological Service. By that time, Météo-France (MFR) estimated 10‑minute winds of 65 km/h (40 mph). Over the subsequent few days, wind shear caused the convection to wax and wane over Eline's center, limiting the thunderstorms to the southern periphery. The track shifted more to
22087104
2008 Pacific hurricane season


. Despite strong easterly wind shear, shower and thunderstorm activity formed close enough to the center for the disturbance to become a tropical depression around 06:00 UTC on September 2. A brief relaxation in upper-level winds allowed the depression to intensify into Tropical Storm Karina six hours later before wind shear once again increased, leading to a steady weakening trend and degeneration to a remnant low by 18:00 UTC on September 3. A tropical wave emerged from Africa on August 19, the northern half of which spawned Hurricane Hanna while the second half
5065304
Cyclone Haruna


were outbreaks of various diseases in the storm's aftermath. In the middle of February, an area of convection, or thunderstorms, persisted in the Mozambique channel. It had an associated circulation and rainbands to the east of the center, and was related to the monsoon trough. The system was located within an area of warm sea surface temperatures of over and steadily decreasing wind shear. A ridge to the south caused the system to initially track to the north. By February 16, the system had moved over Mozambique and turned
9387533
Air-mass thunderstorm


storm's low level inflow, and quickly causes dissipation. Waterspouts, small hail, and strong wind gusts can occur in association with these thunderstorms. Also known as single cell thunderstorms, these are the typical summer thunderstorms in many temperate locales. They also occur in the cool unstable air which often follows the passage of a cold front from the sea during winter. Within a cluster of thunderstorms, the term "cell" refers to each separate principal updraft. Thunderstorm cells occasionally form in isolation, as the occurrence of one thunderstorm
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