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83-509: Northwest Independent School District (Northwest ISD) is a North Texas public school district with its headquarters in the city of Fort Worth , Texas ( USA ). with a Justin postal address. The school district is named for its location in the northwestern area of the Dallas Fort Worth Metroplex . The school district lies in three North Texas counties: Denton County , Tarrant County and Wise County . The district serves

166-572: A lightning storm , is a storm characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere , known as thunder . Relatively weak thunderstorms are sometimes called thundershowers . Thunderstorms occur in a type of cloud known as a cumulonimbus . They are usually accompanied by strong winds and often produce heavy rain and sometimes snow , sleet , or hail , but some thunderstorms produce little precipitation or no precipitation at all. Thunderstorms may line up in

249-651: A T0 for extremely weak tornadoes to T11 for the most powerful known tornadoes. Doppler radar data, photogrammetry , and ground swirl patterns (cycloidal marks) may also be analyzed to determine intensity and award a rating. Waterspouts have similar characteristics as tornadoes, characterized by a spiraling funnel-shaped wind current that form over bodies of water, connecting to large cumulonimbus clouds. Waterspouts are generally classified as forms of tornadoes, or more specifically, non- supercelled tornadoes that develop over large bodies of water. These spiralling columns of air frequently develop within tropical areas close to

332-481: 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, sometimes along a front . However, some kind of cloud forcing , whether it is a front, shortwave trough, or another system is needed for the air to rapidly accelerate upward. As the warm, moist air moves upward, it cools, condenses , and forms a cumulonimbus cloud that can reach heights of over 20 kilometres (12 mi). As

415-452: A few nights each summer when the low temperature exceeds 80 °F (27 °C). Summer daytime temperatures frequently exceed 100 °F (38 °C). Air conditioners are recommended for maximum comfort indoors and while traveling via automobile. Throughout the year, rainfall occurs more frequently during the night. Usually, periods of rainy weather last for only a day or two, and are followed by several days with fair skies. A large part of

498-404: A high frequency for cloud-to-ground lightning, like Florida, lightning causes several fatalities per year, most commonly to people working outside. Acid rain is also a frequent risk produced by lightning. Distilled water has a neutral pH of 7. "Clean" or unpolluted rain has a slightly acidic pH of about 5.2, because carbon dioxide and water in the air react together to form carbonic acid ,

581-500: A local thunderstorm. During a thunderstorm, pollen grains can absorb moisture and then burst into much smaller fragments with these fragments being easily dispersed by wind. While larger pollen grains are usually filtered by hairs in the nose, the smaller pollen fragments are able to pass through and enter the lungs, triggering the asthma attack. Most thunderstorms come and go fairly uneventfully; however, any thunderstorm can become severe , and all thunderstorms, by definition, present

664-707: A much larger area that includes many northern rural counties along the Red River of the South border. Indigenous tribes in North Texas included the Caddo , Tawakoni , Wichita , Kickapoo , and Comanche . With European colonization, Mexican independence , and Texan independence and annexation to the United States , many of these tribes experienced demographic decline through relocation, slavery, etc. Since European colonization and

747-505: A prominent feature and tracking it from scan to scan. A back-building thunderstorm, commonly referred to as a training thunderstorm , is a thunderstorm in which new development takes place on the upwind side (usually the west or southwest side in the Northern Hemisphere ), such that the storm seems to remain stationary or propagate in a backward direction. Though the storm often appears stationary on radar, or even moving upwind, this

830-511: A record-setting 12.8 inches of snow fell in February 2010. Periods of extreme cold that occasionally occur are short-lived, so that even in January mild weather occurs frequently. The highest temperatures of summer are associated with fair skies, and moderate to high humidities. Characteristically, hot spells in summer are broken into three- to five-day periods by thunderstorm activity. There are only

913-445: A series or become a rainband , known as a squall line . Strong or severe thunderstorms include some of the most dangerous weather phenomena, including large hail, strong winds, and tornadoes . Some of the most persistent severe thunderstorms, known as supercells , rotate as do cyclones. While most thunderstorms move with the mean wind flow through the layer of the troposphere that they occupy, vertical wind shear sometimes causes

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996-506: A storm arises quickly and unexpectedly. Preparing the home by removing dead or rotting limbs and trees, which can be blown over in high winds, can also significantly reduce the risk of property damage and personal injury. The National Weather Service (NWS) in the United States recommends several precautions that people should take if thunderstorms are likely to occur: While safety and preparedness often overlap, "thunderstorm safety" generally refers to what people should do during and after

1079-421: A storm. The American Red Cross recommends that people follow these precautions if a storm is imminent or in progress: The NWS stopped recommending the "lightning crouch" in 2008 as it does not provide a significant level of protection and will not significantly lower the risk of being killed or injured from a nearby lightning strike. Thunderstorms occur throughout the world, even in the polar regions, with

1162-683: A weak acid (pH 5.6 in distilled water), but unpolluted rain also contains other chemicals. Nitric oxide present during thunderstorm phenomena, caused by the oxidation of atmospheric nitrogen, can result in the production of acid rain, if nitric oxide forms compounds with the water molecules in precipitation, thus creating acid rain. Acid rain can damage infrastructures containing calcite or certain other solid chemical compounds. In ecosystems, acid rain can dissolve plant tissues of vegetations and increase acidification process in bodies of water and in soil , resulting in deaths of marine and terrestrial organisms. Any thunderstorm that produces hail that reaches

1245-461: Is a polar molecule that can carry a charge, so it is capable of creating the charge separation needed to produce lightning). These electrical discharges can be up to a thousand times more powerful than lightning on the Earth. The water clouds can form thunderstorms driven by the heat rising from the interior. The clouds of Venus may also be capable of producing lightning ; some observations suggest that

1328-596: Is a complex of thunderstorms that becomes organized on a scale larger than the individual thunderstorms but smaller than extratropical cyclones , and normally persists for several hours or more. A mesoscale convective system's overall cloud and precipitation pattern may be round or linear in shape, and include weather systems such as tropical cyclones , squall lines , lake-effect snow events, polar lows , and mesoscale convective complexes (MCCs), and they generally form near weather fronts . Most mesoscale convective systems develop overnight and continue their lifespan through

1411-435: Is an illusion. The storm is really a multi-cell storm with new, more vigorous cells that form on the upwind side, replacing older cells that continue to drift downwind. When this happens, catastrophic flooding is possible. In Rapid City, South Dakota , in 1972, an unusual alignment of winds at various levels of the atmosphere combined to produce a continuously training set of cells that dropped an enormous quantity of rain upon

1494-474: Is issued if a thunderstorm becomes severe, or will soon turn severe. In Canada, a rainfall rate greater than 50 millimetres (2 in) in one hour, or 75 millimetres (3 in) in three hours, is also used to indicate severe thunderstorms. Severe thunderstorms can occur from any type of storm cell. However, multicell , supercell , and squall lines represent the most common forms of thunderstorms that produce severe weather. A mesoscale convective system (MCS)

1577-556: Is known, then the total energy of a thunderstorm can be calculated. In a typical thunderstorm, approximately 5×10 kg of water vapor are lifted, and the amount of energy released when this condenses is 10 joules . This is on the same order of magnitude of energy released within a tropical cyclone, and more energy than that released during the atomic bomb blast at Hiroshima, Japan in 1945 . The Fermi Gamma-ray Burst Monitor results show that gamma rays and antimatter particles ( positrons ) can be generated in powerful thunderstorms. It

1660-525: 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 or direction, the downdraft will be separated from the updraft, and the storm may become a supercell , where the mature stage can sustain itself for several hours. In the dissipation stage, the thunderstorm is dominated by the downdraft. If atmospheric conditions do not support super cellular development, this stage occurs rather quickly, approximately 20–30 minutes into

1743-422: Is mainly inflicted by downburst winds, large hailstones, and flash flooding caused by heavy precipitation . Stronger thunderstorm cells are capable of producing tornadoes and waterspouts . There are three types of thunderstorms: single-cell , multi-cell , and supercell . Supercell thunderstorms are the strongest and most severe. Mesoscale convective systems formed by favorable vertical wind shear within

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1826-468: Is more of a factor with thunderstorms with heavy precipitation (HP) than with thunderstorms with low precipitation (LP). When thunderstorms merge, which is most likely when numerous thunderstorms exist in proximity to each other, the motion of the stronger thunderstorm normally dictates the future motion of the merged cell. The stronger the mean wind, the less likely other processes will be involved in storm motion. On weather radar , storms are tracked by using

1909-741: 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 24 kilometres (15 mi) wide. Research has shown that at least 90 percent of supercells cause severe weather . These storms can produce destructive tornadoes , extremely large hailstones (10 centimetres or 4 inches diameter), straight-line winds in excess of 130 km/h (81 mph), and flash floods . In fact, research has shown that most tornadoes occur from this type of thunderstorm. Supercells are generally

1992-412: Is one of the most significant thunderstorm hazards to aircraft. When hail stones exceed 13 millimetres (0.5 in) in diameter, planes can be seriously damaged within seconds. The hailstones accumulating on the ground can also be hazardous to landing aircraft. Wheat, corn, soybeans, and tobacco are the most sensitive crops to hail damage. Hail is one of Canada's most costly hazards. Hailstorms have been

2075-411: Is suggested that the antimatter positrons are formed in terrestrial gamma-ray flashes (TGF). TGFs are brief bursts occurring inside thunderstorms and associated with lightning. The streams of positrons and electrons collide higher in the atmosphere to generate more gamma rays. About 500 TGFs may occur every day worldwide, but mostly go undetected. In more contemporary times, thunderstorms have taken on

2158-586: Is the most common type of thunderstorm development. Mature thunderstorms are found near the center of the cluster, while dissipating thunderstorms exist on their downwind side. Multicell storms form as clusters of storms but may then evolve into one or more squall lines . While each cell of the cluster may only last 20 minutes, the cluster itself may persist for hours at a time. They often arise from convective updrafts in or near mountain ranges and linear weather boundaries, such as strong cold fronts or troughs of low pressure. These type of storms are stronger than

2241-538: Is uncommon. The average length of the warm season (freeze-free period) is about 249 days. The average last occurrence of 32 °F (0 °C) or below is mid March and the average first occurrence of 32 °F or below is in late November. Although the terms "Northeastern Texas" or "North Texas" are not official state designations, the Texas State Data Center and Office of the State Demographer lists

2324-437: Is usually caused by the heavy liquid precipitation that accompanies it. Flash floods are most common in arid regions as well as densely populated urban environments, where few plants, and bodies of water are present to absorb and contain the extra water. Flash flooding can be hazardous to small infrastructure, such as bridges, and weakly constructed buildings. Plants and crops in agricultural areas can be destroyed and devastated by

2407-947: The Dallas Wings of the WNBA plays in Arlington. The area is also home to many minor league professional teams and four colleges that compete in NCAA Division I athletics. ^- Indicates year team relocated to the area ^- Indicates year team relocated to the area Texas A&M University–Commerce The headquarters for both the Big 12 and Conference USA are located in Irving , and the Southland Conference headquarters are in Frisco . Thunderstorm A thunderstorm , also known as an electrical storm or

2490-661: The Doppler on Wheels , vehicles with mounted automated weather stations , weather balloons , and unmanned aircraft to investigate thunderstorms expected to produce severe weather. Lightning is detected remotely using sensors that detect cloud-to-ground lightning strokes with 95 percent accuracy in detection and within 250 metres (820 ft) of their point of origin. Thunderstorms strongly influenced many early civilizations. Greeks believed that they were battles waged by Zeus , who hurled lightning bolts forged by Hephaestus . Some American Indian tribes associated thunderstorms with

2573-490: The Earth's atmosphere . In the mature stage of a thunderstorm, the warmed air continues to rise until it reaches an area of warmer air and can rise no farther. Often this 'cap' is the tropopause . The air is instead forced to spread out, giving the storm a characteristic anvil shape. The resulting cloud is called cumulonimbus incus . The water droplets coalesce into larger and heavier droplets and freeze to become ice particles. As these fall, they melt to become rain. If

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2656-438: 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

2739-628: The Rocky Mountains as part of the North American Monsoon regime. In the Northeast , storms take on similar characteristics and patterns as the Midwest, but with less frequency and severity. During the summer, air-mass thunderstorms are an almost daily occurrence over central and southern parts of Florida. If the quantity of water that is condensed in and subsequently precipitated from a cloud

2822-756: The Texas Rangers , named after the statewide law enforcement agency . The National Basketball Association expanded into North Texas in 1980 when the Dallas Mavericks were added to the league. The fourth sport was added in 1993 when the Minnesota North Stars of the National Hockey League moved to Dallas, becoming the Dallas Stars . The Major League Soccer team FC Dallas is based in Frisco, and

2905-517: The Thunderbird , who they believed was a servant of the Great Spirit . The Norse considered thunderstorms to occur when Thor went to fight Jötnar , with the thunder and lightning being the effect of his strikes with the hammer Mjölnir . Hinduism recognizes Indra as the god of rain and thunderstorms. Christian doctrine accepts that fierce storms are the work of God. These ideas were still within

2988-537: The United States rainfall climatology over the Great Plains since they bring the region about half of their annual warm season rainfall. The two major ways thunderstorms move are via advection of the wind and propagation along outflow boundaries towards sources of greater heat and moisture. Many thunderstorms move with the mean wind speed through the Earth's troposphere , the lowest 8 kilometres (5.0 mi) of

3071-437: The equator , but are less common within areas of high latitude . Flash flooding is the process where a landscape, most notably an urban environment, is subjected to rapid floods. These rapid floods occur more quickly and are more localized than seasonal river flooding or areal flooding and are frequently (though not always) associated with intense rainfall. Flash flooding can frequently occur in slow-moving thunderstorms and

3154-418: The lifted index can be used to assist in determining potential upward vertical development of clouds. Generally, thunderstorms require three conditions in order to form: All thunderstorms, regardless of type, go through three stages: the developing stage , the mature stage , and the dissipation stage . The average thunderstorm has a 24 km (15 mi) diameter. Depending on the conditions present in

3237-504: The water vapor in that rising air condenses . When the moisture condenses, it releases energy known as latent heat of condensation, which allows the rising packet of air to cool less than the cooler surrounding air continuing the cloud's ascension. If enough instability is present in the atmosphere, this process will continue long enough for cumulonimbus clouds to form and produce lightning and thunder . Meteorological indices such as convective available potential energy (CAPE) and

3320-475: The 18th century. Beyond the Earth's atmosphere, thunderstorms have also been observed on the planets of Jupiter , Saturn , Neptune , and, probably, Venus . Warm air has a lower density than cool air, so warmer air rises upwards and cooler air will settle at the bottom (this effect can be seen with a hot air balloon ). Clouds form as relatively warmer air, carrying moisture, rises within cooler air. The moist air rises, and, as it does so, it cools and some of

3403-481: 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, which can be potentially hazardous. Damage that results from thunderstorms

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3486-406: The annual precipitation results from thunderstorm activity, with occasional heavy rainfall over brief periods of time. Thunderstorms occur throughout the year, but are most frequent in the spring and early summer months. Hail falls on about two or three days a year, ordinarily with only slight and scattered damage. Windstorms occurring during thunderstorm activity are sometimes destructive. Snowfall

3569-589: The atmosphere, each of these three stages take an average of 30 minutes. The first stage of a thunderstorm is the cumulus stage or developing stage. During this stage, masses of moisture are lifted upwards into the atmosphere. The trigger for this lift can be solar illumination , where the heating of the ground produces thermals , or where two winds converge forcing air upwards, or where winds blow over terrain of increasing elevation. The moisture carried upward cools into liquid drops of water due to lower temperatures at high altitude, which appear as cumulus clouds. As

3652-758: The back edge of the rain shield associated with mature squall lines, a wake low can form, which is a mesoscale low pressure area that forms behind the mesoscale high pressure system normally present under the rain canopy, which are sometimes associated with a heat burst . This kind of storm is also known as "Wind of the Stony Lake" ( simplified Chinese : 石湖风 ; traditional Chinese : 石湖風 ; shi2 hu2 feng1) in southern China. Supercell storms are large, usually severe , quasi-steady-state storms that form in an environment where wind speed or wind direction varies with height (" wind shear "), and they have separate downdrafts and updrafts (i.e., where its associated precipitation

3735-402: The bulk of the occurrences from May through September. Cheyenne, Wyoming , is North America's most hail-prone city with an average of nine to ten hailstorms per season. In South America, areas prone to hail are cities like Bogotá, Colombia. Hail can cause serious damage, notably to automobiles , aircraft, skylights, glass-roofed structures, livestock, and most commonly, farmers' crops . Hail

3818-501: The cause of costly and deadly events throughout history. One of the earliest recorded incidents occurred around the 9th century in Roopkund , Uttarakhand, India. The largest hailstone in terms of maximum circumference and length ever recorded in the United States fell in 2003 in Aurora, Nebraska , United States. A tornado is a violent, rotating column of air in contact with both the surface of

3901-481: The cities of Justin , Roanoke , Trophy Club , Northlake , Marshall Creek , Corral City , and small portions of Flower Mound and Southlake in Denton County. The Wise County towns of Aurora , Rhome , Pecan Acres , Newark , and portions of New Fairview also lie within the district. The Tarrant County portion of the district includes Haslet , Avondale, parts of Westlake , Keller , and Fort Worth . In all,

3984-431: The danger of lightning . Thunderstorm preparedness and safety refers to taking steps before, during, and after a thunderstorm to minimize injury and damage. Preparedness refers to precautions that should be taken before a thunderstorm. Some preparedness takes the form of general readiness (as a thunderstorm can occur at any time of the day or year). Preparing a family emergency plan, for example, can save valuable time if

4067-497: The development of organized convection. This term technically applies to a single thunderstorm with one main updraft. Also known as air-mass thunderstorms , these are the typical summer thunderstorms in many temperate locales. They also occur in the cool unstable air that 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

4150-418: The district is approximately 234 square miles. As of September 2021, Northwest ISD educates over 27,000 students in its thirty educational campuses. Northwest ISD is expected to have up to 35,000 students by the early 2020s, and is the first fastest-growing school district in North Texas. There are 108 active housing communities within the attendance boundaries of Northwest ISD. For the 2013-2014 school year,

4233-637: The earth and a cumulonimbus cloud (otherwise known as a thundercloud) or, in rare cases, the base of a cumulus cloud . Tornadoes come in many sizes but are typically in the form of a visible condensation funnel , whose narrow end touches the earth and is often encircled by a cloud of debris and dust . Most tornadoes have wind speeds between 40 and 110 mph (64 and 177 km/h), are approximately 75 metres (246 ft) across, and travel several kilometers (a few miles) before dissipating. Some attain wind speeds of more than 300 mph (480 km/h), stretch more than 1,600 metres (1 mi) across, and stay on

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4316-570: The following counties as belonging to the North Central Texas Council of Governments (NCTCOG): The Texas State Demographer also lists the following regional county groupings, some or all of which are often included in the informal meaning of the terms "North Texas" or "North Central Texas". Nortex Regional Planning Commission : Texoma Council of Governments : Additionally, some other Texas counties contiguous with those named above are sometimes included in

4399-429: The force exerted by downburst winds. Downburst winds are usually formed in areas when high pressure air systems of downdrafts begin to sink and displace the air masses below it, due to their higher density. When these downdrafts reach the surface, they spread out and turn into the destructive straight-horizontal winds. Thunderstorm asthma is the triggering of an asthma attack by environmental conditions directly caused by

4482-739: The force of raging water. Automobiles parked within affected areas can also be displaced. Soil erosion can occur as well, exposing risks of landslide phenomena. Downburst winds can produce numerous hazards to landscapes experiencing thunderstorms. Downburst winds are generally very powerful, and are often mistaken for wind speeds produced by tornadoes, due to the concentrated amount of force exerted by their straight-horizontal characteristic. Downburst winds can be hazardous to unstable, incomplete, or weakly constructed infrastructures and buildings. Agricultural crops, and other plants in nearby environments can be uprooted and damaged. Aircraft engaged in takeoff or landing can crash. Automobiles can be displaced by

4565-427: 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

4648-697: The four major professional sports leagues. Major professional sports first came to the area in 1960, when the Dallas Cowboys began competing in the National Football League and the Dallas Texans began competing in the American Football League . (The Texans later relocated to Kansas City and became the Chiefs ). In 1972, Major League Baseball's Washington Senators moved to Arlington to become

4731-534: The general meaning of "North Texas". In the North Texas region there is one combined statistical area , three metropolitan areas , and seven micropolitan areas . Metropolitan statistical areas (MSAs) Micropolitan statistical areas (μSAs) Metropolitan statistical areas (MSAs) Micropolitan statistical areas (μSAs) Micropolitan statistical Areas (μSAs) Dallas–Fort Worth metroplex Wichita Falls metropolitan area Sherman–Denison metropolitan area The North Texas region has teams from

4814-579: The greatest frequency in tropical rainforest areas, where they may occur nearly daily. At any given time, approximately 2,000 thunderstorms are occurring on Earth. Kampala and Tororo in Uganda have each been mentioned as the most thunderous places on Earth, a claim also made for Singapore and Bogor on the Indonesian island of Java . Other cities known for frequent storm activity include Darwin , Caracas, Manila and Mumbai . Thunderstorms are associated with

4897-469: The ground for more than 100 kilometres (dozens of miles). The Fujita scale and the Enhanced Fujita Scale rate tornadoes by damage caused. An EF0 tornado, the weakest category, damages trees but does not cause significant damage to structures. An EF5 tornado, the strongest category, rips buildings off their foundations and can deform large skyscrapers. The similar TORRO scale ranges from

4980-449: The ground is known as a hailstorm. Thunderclouds that are capable of producing hailstones are often seen obtaining green coloration. Hail is more common along mountain ranges because mountains force horizontal winds upwards (known as orographic lifting ), thereby intensifying the updrafts within thunderstorms and making hail more likely. One of the more common regions for large hail is across mountainous northern India, which reported one of

5063-410: The highest hail-related death tolls on record in 1888. China also experiences significant hailstorms. Across Europe, Croatia experiences frequent occurrences of hail. In North America, hail is most common in the area where Colorado , Nebraska , and Wyoming meet, known as "Hail Alley". Hail in this region occurs between the months of March and October during the afternoon and evening hours, with

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5146-419: The independence movements, the North Texas area was settled and most notably developed the cities of Dallas and Fort Worth. The North Texas climate is subtropical with hot summers. It is also continental , characterized by a wide annual temperature range. Average annual precipitation also varies considerably, ranging from less than 28 to more than 48 inches (700–1200 mm). Severe storms are frequent in

5229-402: 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, normally greater than 25 knots (13 m/s) in

5312-532: The life of the thunderstorm. The downdraft will push down out of the thunderstorm, hit the ground and spread out. This phenomenon is known as a downburst . The cool air carried to 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

5395-609: The lowest 6 kilometres (3.7 mi) 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 31.8 millimetres (1.25 in) favor the development of organized thunderstorm complexes. Those with heavy rainfall normally have precipitable water values greater than 36.9 millimetres (1.45 in). Upstream values of CAPE of greater than 800 J/kg are usually required for

5478-449: The mainstream as late as the 18th century. Martin Luther was out walking when a thunderstorm began, causing him to pray to God for being saved and promising to become a monk. Thunderstorms, evidenced by flashes of lightning , on Jupiter have been detected and are associated with clouds where water may exist as both a liquid and ice, suggesting a mechanism similar to that on Earth. (Water

5561-653: The most powerful thunderstorms over the United States occur in the Midwest and the Southern states . These storms can produce large hail and powerful tornadoes. Thunderstorms are relatively uncommon along much of the West Coast of the United States , but they occur with greater frequency in the inland areas, particularly the Sacramento and San Joaquin Valleys of California. In spring and summer, they occur nearly daily in certain areas of

5644-530: The next day. They tend to form when the surface temperature varies by more than 5 °C (9 °F) between day and night. The type that forms during the warm season over land has been noted across North America, Europe, and Asia, with a maximum in activity noted during the late afternoon and evening hours. Forms of MCS that develop in the tropics are found in use either the Intertropical Convergence Zone or monsoon troughs , generally within

5727-526: The occurrence of one thunderstorm can develop an outflow boundary that 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 and occur randomly in time and space, making them difficult to forecast. Single-cell thunderstorms normally last 20–30 minutes. This

5810-498: The phenomena of thunderstorms and have numerous hazards towards landscapes and populations. One of the more significant hazards lightning can pose is the wildfires they are capable of igniting. Under a regime of low precipitation (LP) thunderstorms, where little precipitation is present, rainfall cannot prevent fires from starting when vegetation is dry as lightning produces a concentrated amount of extreme heat. Direct damage caused by lightning strikes occurs on occasion. In areas with

5893-426: The rising air reaches its dew point temperature, water vapor condenses into water droplets or ice, reducing pressure locally within the thunderstorm cell. Any precipitation falls the long distance through the clouds towards the Earth's surface. As the droplets fall, they collide with other droplets and become larger. The falling droplets create a downdraft as it pulls cold air with it, and this cold air spreads out at

5976-489: The role of a scientific curiosity. Every spring, storm chasers head to the Great Plains of the United States and the Canadian Prairies to explore the scientific aspects of storms and tornadoes through use of videotaping. Radio pulses produced by cosmic rays are being used to study how electric charges develop within thunderstorms. More organized meteorological projects such as VORTEX2 use an array of sensors, such as

6059-503: The same area, resulting in devastating flash flooding . A similar event occurred in Boscastle , England, on 16 August 2004, and over Chennai on 1 December 2015. Each year, many people are killed or seriously injured by severe thunderstorms despite the advance warning . While severe thunderstorms are most common in the spring and summer, they can occur at just about any time of the year. Cloud-to-ground lightning frequently occurs within

6142-802: The school district was rated as " meeting standard " by the Texas Education Agency , which is currently the highest ranking given under the STAAR system. North Texas North Texas is centered upon the Dallas–Fort Worth metroplex, the largest metropolitan area in Texas and the Southern United States . People in the Dallas and Fort Worth areas sometimes use the terms Metroplex , DFW , and North Texas interchangeably. However, North Texas refers to

6225-526: The single-cell storm, yet much weaker than the supercell storm. Hazards with the multicell cluster include moderate-sized hail, flash flooding, and weak tornadoes. A squall line is an elongated line of severe thunderstorms that can form along or ahead of a cold front . In the early 20th century, the term was used as a synonym for cold front . The squall line contains heavy precipitation , hail , frequent lightning , strong straight line winds, and possibly tornadoes and waterspouts . Severe weather in

6308-408: The spring and summer, as the area lies in the southern section of " tornado alley ". South is the prevailing wind direction, and southerly winds are frequently high and persist for several days. Strong northerly winds often occur during the passage of cold fronts. Winters can be mild, but northers occur about three times each month, and often are accompanied by sudden drops in temperature. In Dallas,

6391-443: The strongest type of thunderstorm. In the United States, a thunderstorm is classed as severe if winds reach at least 93 kilometres per hour (58 mph), hail is 25 millimetres (1 in) in diameter or larger, or if funnel clouds or tornadoes are reported. Although a funnel cloud or tornado indicates a severe thunderstorm, a tornado warning is issued in place of a severe thunderstorm warning . A severe thunderstorm warning

6474-592: 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 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

6557-453: 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-ground lightning that accompanies them. Several means are used to study thunderstorms: weather radar , weather stations , and video photography. Past civilizations held various myths concerning thunderstorms and their development as late as

6640-552: The updraft is strong enough, the droplets are held aloft long enough to become so large that they do not melt completely but fall as hail . While updrafts 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

6723-464: The various monsoon seasons around the globe, and they populate the rainbands of tropical cyclones . In temperate regions, they are most frequent in spring and summer, although they can occur along or ahead of cold fronts at any time of year. They may also occur within a cooler air mass following the passage of a cold front over a relatively warmer body of water. Thunderstorms are rare in polar regions because of cold surface temperatures. Some of

6806-539: The warm season between spring and fall. More intense systems form over land than over water. One exception is that of lake-effect snow bands, which form due to cold air moving across relatively warm bodies of water, and occurs from fall through spring. Polar lows are a second special class of MCS. They form at high latitudes during the cold season. Once the parent MCS dies, later thunderstorm development can occur in connection with its remnant mesoscale convective vortex (MCV). Mesoscale convective systems are important to

6889-454: The water vapor condenses into liquid, latent heat is released, which warms the air, causing it to become less dense than the surrounding, drier air. The air tends to rise in an updraft through the process of convection (hence the term convective precipitation ). This process creates a low-pressure zone within and beneath the forming thunderstorm. In a typical thunderstorm, approximately 500 million kilograms of water vapor are lifted into

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