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pp-move|small=yesredirect|Electrical stormA thunderstorm , also known as an electrical storm , a lightning storm , thundershower or simply a storm is a form of weather characterized by the presence of lightning and its acoustics|acoustic effect on the Earth's atmosphere known as thunder .cite web | date = 21 April 2005 | url = http://www.weather.gov/glossary/index.php? letter=t | title = Weather Glossary – T | author = National Weather Service | publisher= National Oceanic and Atmospheric Administration | accessdate = 2006-08-23 The meteorologically assigned cloud type associated with the thunderstorm is the cumulonimbus . Thunderstorms are usually accompanied by Wind|strong winds , heavy rain (meteorology)|heavy rain and sometimes Thundersnow|snow , Ice pellets|sleet , hail , or Dry thunderstorm|no precipitation at all. Those that cause hail to fall are called hailstorms. Thunderstorms may thunderstorm training|line up in a series or rainband , known as a squall line . Strong or severe thunderstorms may rotate, known as supercell s. While most thunderstorms move with the mean wind flow through the layer of the troposphere that they occupy, vertical wind shear 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. They can occur inside warm, moist air masses and at fronts. As the warm, moist air moves upward, it cools, condenses, and forms cumulonimbus clouds that can reach heights of over 20& nbsp;km. As the rising air reaches its dew point , water droplets and ice form and begin falling 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 of air that spreads out at the Earth's surface and causes strong winds associated commonly with thunderstorms.
Thunderstorms can generally form and develop in any geographic location, perhaps most frequently within areas located at Mid-latitudes|mid-latitude when warm moist air collides with cooler air.cite web |publisher= National Oceanic and Atmospheric Administration |author= National Severe Storms Laboratory |title=tornadoes...''Nature's Most Violent Storms |url= http://www.nssl.noaa.gov/edu/safety/tornadoguide.html |date=September 1992 |work=A PREPAREDNESS GUIDE|accessdate=2008-08-03 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 to populations and landscapes. Damage that results from thunderstorms is mainly inflicted by downburst winds, large hail stones, and flash flooding caused by heavy precipitation (meteorology)|precipitation . Stronger thunderstorm cells are capable of producing tornado es and waterspout s. A 1953 study found that the average thunderstorm over several hours expends enough energy to equal 50 A-bombs types that was dropped on Hiroshima, Japan during World War Two. http://books.google.com/books? id=zdwDAAAAMBAJ& pg=PA86& dq=true#v=onepage& q=true& f=true "Thunderstorm Energy Equals 50 A-bombs." Popular Mechanics , January 1953, p. 86, bottom of page WeatherThere are four types of thunderstorms: single-cell, multicell cluster, multicell lines, and supercell s. Supercell thunderstorms are the strongest and the most associated with severe weather phenomena. Mesoscale convective system s formed by favorable vertical wind shear within the tropics and subtropics are responsible for the development of Tropical cyclone|hurricane s. Dry thunderstorm s, with no precipitation, can cause the outbreak of wildfires with the heat generated from the Lightning#Cloud-to-ground lightning|cloud-to-ground lightning that accompanies them. Several methods are used to study thunderstorms, such as weather radar , weather station s, and video photography. Past civilizations held various myths concerning thunderstorms and their development as late as the 18th century. Other than within the Earth's atmosphere , thunderstorms have also been observed on Jupiter and Venus .
Life cycle
see also|Cloud Warm air has a lower density than cool air, so warm air rises within cooler air,cite book|url= http://books.google.com/? id=PDtIAAAAIAAJ& pg=PA462& lpg=PA462& dq=density+varies+by+temperature+book& q=|title=Civil engineers' pocket book: a reference-book for engineers, contractors|author=Albert Irvin Frye|page=462|publisher=D. Van Nostrand Company|year=1913|accessdate=2009-08-31 similar to hot air balloon s.cite book | url = http://books.google.com/? id=ssO_19TRQ9AC& pg=PA112& dq=Kongming+balloon | title = Ancient Chinese Inventions | author = Yikne Deng | publisher = Chinese International Press | isbn=978-7-5085-0837-5 | year=2005 | pages = 112–13 | accessdate = 2009-06-18 Clouds form as relatively warmer air carrying moisture rises within cooler air. As the moist air rises, it cools causing some of the water vapor in the rising packet of air to condensation|condense .cite web|author=FMI|year=2007|url= http://www.zamg.ac.at/docu/Manual/SatManu/main.htm? /docu/Manual/SatManu/CMs/FgStr/backgr.htm|title=Fog And Stratus – Meteorological Physical Background|publisher=Zentralanstalt für Meteorologie und Geodynamik|accessdate=2009-02-07 When the moisture condenses, it releases energy known as latent heat of fusion, which allows the rising packet of air to cool less than the surrounding air,cite book|url= http://books.google.com/? id=RRSzR4NQdGkC& pg=PA20& lpg=PA20& dq=cloud+formation+latent+heat+book& q=|title=Storm world: hurricanes, politics, and the battle over global warmin|author=Chris C. Mooney|page=20|isbn=978-0-15-101287-9|publisher=Houghton Mifflin Harcourt|year=2007|accessdate=2009-08-31 continuing the cloud's ascension. If enough Convective available potential energy|instability is present in the atmosphere, this process will continue long enough for Cumulonimbus|cumulonimbus clouds to form, which support lightning and thunder. Meteorological indices such as convective available potential energy (CAPE) and the lifted index can be used to assist in determining upward vertical development of clouds.cite journal |author= David O. Blanchard |title= Assessing the Vertical Distribution of Convective Available Potential Energy |journal= Weather and Forecasting |volume= 13 |issue= 3 |pages= 870–7 |publisher= American Meteorological Society |date= September 1998 |year= 1998 |url= http://ams.allenpress.com/perlserv/? request=get-abstract& doi=10.1175%2F1520-0434(1998)013%3C0870%3AATVDOC%3E2.0.CO%3B2 |doi= 10.1175/1520-0434(1998)013<0870:ATVDOC>2.0.CO;2|accessdate=2009-09-09 |bibcode=1998WtFor..13..870B Generally, thunderstorms require three conditions to form: # Moisture # An unstable airmass # A lifting force (heat)
All thunderstorms, regardless of type, go through three stages: the developing stage , the mature stage , and the dissipation stage .cite book |title=Extreme Weather |author=Micheal H. Mogil |year=2007 |publisher=Black Dog & Leventhal Publisher |location=New York |isbn=978-1-57912-743-5 |pages=210–211 The average thunderstorm has a convert|24|km|mi|abbr=on diameter. Depending on the conditions present in the atmosphere, these three stages take an average of 30 minutes to go through.cite web|url= http://www.nssl.noaa.gov/primer/tstorm/tst_basics.html|title=A Severe Weather Primer: Questions and Answers about Thunderstorms |author=National Severe Storms Laboratory| publisher= National Oceanic and Atmospheric Administration |date=2006-10-15|accessdate=2009-09-01
Cumulus stage
The first stage of a thunderstorm is the cumulus stage, or developing stage. In this stage, masses of moisture are lifted upwards into the atmosphere. The trigger for this lift 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 cloud|cumulus clouds. As the water vapor condenses into liquid, latent heat is released, which warms the air, causing it to become less dense than the surrounding dry air. The air tends to rise in an updraft through the process of Atmospheric convection|convection (hence the term Precipitation (meteorology)|convective precipitation ). This creates a low pressure area|low-pressure zone beneath the forming thunderstorm. In a typical thunderstorm, approximately 5×108 kilograms|kg of water vapor are lifted into the Earth's atmosphere .cite web|url= http://physics.syr.edu/courses/modules/ENERGY/ENERGY_POLICY/tables.html|title=Rough Values of Various Processes|author=Gianfranco Vidali|year=2009|accessdate=2009-08-31|publisher= University of Syracuse
Mature stage
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 and/or direction the downdraft will be separated from the updraft, and the storm may become a supercell , and the mature stage can sustain itself for several hours. clear
Dissipating stage
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 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 (meteorology)|inflow of relatively warm, moist air and kills the thunderstorm.cite web|author=The Weather World 2010 Project|publisher=University of Illinois|url= http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/svr/comp/wind/home.rxml|title=Vertical Wind Shear|accessdate=2006-10-21|date=2009-09-03 The downdraft hitting the ground creates an outflow boundary . This can cause downbursts, a potential hazardous condition for aircraft that fly through it, as a substantial change in wind speed and direction occurs, resulting in decrease of lift of the aircraft. The stronger the outflow boundary is, the stronger the resultant vertical wind shear becomes.cite book|author=T. T. Fujita|year=1985|title=The Downburst, microburst and macroburst: SMRP Research Paper 210|authorlink=Ted Fujita
Classification
There are four main types of thunderstorms: single-cell, multicell, squall line (also called multicell 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 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.
Single-cell
Main|Air-mass thunderstormThis term technically applies to a single thunderstorm with one main updraft. Also known as air-mass thunderstorm s, 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 weather fronts|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 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& nbsp;minutes.
Multicell clusters
This 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 line s. While each cell of the cluster may only last 20& nbsp;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, usually strong cold fronts or troughs of low pressure. These type of storms are stronger than 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.
Multicell lines
Main|Squall lineSee also|List of derecho eventsA squall line is an elongated line of thunderstorms#Severe_thunderstorms|severe thunderstorms that can form along and/or ahead of a cold front .cite web|url= http://amsglossary.allenpress.com/glossary/search? id=squall-line1|author=Glossary of Meteorology|title=Squall line|year=2009|accessdate=2009-06-14|publisher= American Meteorological Society cite web|url= http://amsglossary.allenpress.com/glossary/search? id=prefrontal-squall-line1|author=Glossary of Meteorology|title=Prefrontal squall line|year=2009|accessdate=2009-06-14|publisher= American Meteorological Society In the early 20th century, the term was used as a synonym for cold front .cite web|author=University of Oklahoma|year=2004|url= http://weather.ou.edu/~metr4424/Files/Norwegian_Cyclone_Model.pdf|title=The Norwegian Cyclone Model|accessdate=2007-05-17 |archiveurl = http://web.archive.org/web/20060901163934/ http://weather.ou.edu/~metr4424/Files/Norwegian_Cyclone_Model.pdf |archivedate = September 1, 2006 The squall line contains heavy precipitation (meteorology)|precipitation , hail , frequent lightning , strong straight line wind s, and possibly tornado es and waterspouts .cite web|author=Office of the Federal Coordinator for Meteorology|year=2008|url= http://www.ofcm.gov/slso/pdf/slsochp2.pdf|title=Chapter 2: Definitions|pages=2–1|publisher= NOAA |accessdate=2009-05-03 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.cite web|url= http://amsglossary.allenpress.com/glossary/search? p=1& query=bow+echo& submit=Search|author=Glossary of Meteorology|title=Bow echo|year=2009|accessdate=2009-06-14|publisher= American Meteorological Society Tornado es can be found along waves within a line echo wave pattern , or LEWP, where mesoscale low pressure area s are present.cite book|author=Glossary of Meteorology|year=2009|url= http://amsglossary.allenpress.com/glossary/search? id=line-echo-wave-pattern1|title=Line echo wave pattern|publisher= American Meteorological Society |ISBN=1-878220-34-9|accessdate=2009-05-03 Some bow echoes in the summer are called derecho s, and move quite fast through large sections of territory.cite web| url= http://www.spc.noaa.gov/misc/AbtDerechos/derechofacts.htm| title=About Derechos| publisher= Storm Prediction Center , NCEP, NWS, NOAA Web Site| author= Robert H. Johns| coauthors= Jeffry S. Evans| date=2006-04-12| accessdate=2007-06-21 On 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 .cite book |author= Glossary of Meteorology|title=Heat burst |publisher= American Meteorological Society |year= 2009 |url= http://amsglossary.allenpress.com/glossary/search? id=heat-burst1 |isbn= 1-878220-34-9| accessdate=2009-06-14 This kind of storm is also known as "Wind of the Stony Lake" (Traditional Chinese:??? – shi2 hu2 feng1, Simplified Chinese: ???) in southern China.cite web | date = 17 June 2005 | url = http://www.hko.gov.hk/education/edu01met/wxphe/ele_squalle.htm | title = Squall lines and "Shi Hu Feng" – what you want to know about the violent squalls hitting Hong Kong on 9 May 2005 | publisher = Hong Kong Observatory | accessdate = 2006-08-23
Supercells
Main|Supercell Supercell storms are large, severe quasi-steady-state storms with wind speed and direction that vary with height ("wind shear"), separate downdrafts and updrafts (i.e., precipitation is not falling through the updraft) and a strong, rotating updraft (a " mesocyclone "). These storms normally have such powerful updrafts that the top of the cloud (or anvil) can break through the troposphere and reach into the lower levels of the stratosphere and can be convert|15|mi|km|0 wide. At least 90& nbsp;percent of this type of thunderstorm bring severe weather .cite web|url= http://www.crh.noaa.gov/images/unr/soo/scm/ZB06.pdf|title=Operational Forecasting of Supercell Motion: Review and Case Studies Using Multiple Datasets|author=Jon W. Zeitler and Matthew J. Bunkers|date=March 2005|accessdate=2009-08-30|publisher= National Weather Service Forecast Office, Riverton, Wyoming These storms can produce destructive tornadoes, sometimes Fujita scale|F3 or higher, extremely large hailstones (convert|4|in|cm|disp=s diameter), straight-line winds in excess of convert|80|mph|km/h|abbr=on, and flash flood s. In fact, most tornadoes occur from this type of thunderstorm.cite web |date =October 4, 1999 |url= http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/svr/type/spr/home.rxml |title=Supercell Thunderstorms |work=Weather World 2010 Project |publisher=University of Illinois |accessdate=2006-08-23 Supercells are the most powerful type of thunderstorm.
Severe thunderstorms
A severe thunderstorm is a term designating a thunderstorm that has reached a predetermined level of severity. This level is determined by the storm being strong enough to inflict wind or hail damage. A storm is considered severe if winds reach over convert|93|km/h|mph, hail is convert|1|in|mm|1 in diameter or larger, or if funnel cloud s and/or tornado es are reported.cite web | title =Weather Glossary – S | author = National Weather Service | publisher= National Oceanic and Atmospheric Administration | date =2005-04-21 | url = http://www.weather.gov/glossary/index.php? letter=s | accessdate =2007-06-17 cite video | people = Kim Runk | title = 1" Hail | medium = .wmv | publisher = NOAA | location = Silver Spring, Maryland|url= http://www.crh.noaa.gov/crh/One_Inch_Hail_Podcast.wmv |date = 2009cite web|url= http://www.wrh.noaa.gov/psr/pns/2009/April/NewHailCriteria.php? wfo=psr|author= National Weather Service Forecast Office, Phoenix, Arizona |title=New Hail Criteria|accessdate=2009-09-03|date=2009-04-07 Though a funnel cloud or tornado indicates a severe thunderstorm, a tornado warning is issued in place of a severe thunderstorm warning . In Canada , a rainfall rate greater than convert|50|mm|in|sigfig=1 in one hour, or convert|75|mm|in|sigfig=1 in three hours is also used to indicate severe thunderstorms.cite web|url= http://www.on.ec.gc.ca/severe-weather/summerwx_factsheet_e.html|title=Fact Sheet – Summer Severe Weather Warnings|author= Environment Canada Ontario Region|date=2005-05-24|accessdate=2009-09-03 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.
Mesoscale convective systems
See also|Mesoscale convective system A mesoscale convective system ( MCS ) is a complex of thunderstorms that becomes organized on a scale larger than the individual thunderstorms but smaller than extratropical cyclone s, and normally persists for several hours or more.cite web|url= http://amsglossary.allenpress.com/glossary/search? p=1& query=mesoscale+convective+system& submit=Search|title=Mesoscale convective system|year=2009|accessdate=2009-06-27|author=Glossary of Meteorology|publisher= American Meteorological Society A mesoscale convective system's overall cloud and precipitation pattern may be round or linear in shape, and include weather systems such as tropical cyclone s, squall line s, lake-effect snow events, polar low s, and Mesoscale Convective Complex es (MCCs), and generally form near weather front s. Most mesoscale convective systems develop overnight and continue their lifespan through the next day. 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.cite web|author=William R. Cotton, Susan van den Heever, and Israel Jirak|year=2003|url= http://rams.atmos.colostate.edu/at540/fall03/fall03Pt9.pdf|title=Conceptual Models of Mesoscale Convective Systems: Part 9|publisher= Colorado State University |accessdate=2008-03-23cite journal|author=C. Morel and S. Senesi|year=2002|url= http://cat.inist.fr/? aModele=afficheN& cpsidt=13876728|title=A climatology of mesoscale convective systems over Europe using satellite infrared imagery. II: Characteristics of European mesoscale convective systems|journal=Quarterly Journal of the Royal Meteorological Society|issn=0035-9009|accessdate=2008-03-02|volume=128|issue=584|pages=1973|doi=10.1256/003590002320603494
Forms of MCS that develop within the tropics use either the Intertropical Convergence Zone or monsoon trough s as a focus for their development, generally within the warm season between spring (season)|spring and fall . More intense systems form over land than over water.cite web|author=Semyon A. Grodsky and James A. Carton|url= http://www.atmos.umd.edu/~carton/pdfs/grodsky& carton03.pdf|date=2003-02-15|publisher= University of Maryland, College Park |title=The Intertropical Convergence Zone in the South Atlantic and the Equatorial Cold Tongue|accessdate=2009-06-05cite book|url= http://books.google.com/? id=HiaP4yJ8wNMC& pg=PA40& lpg=PA40& dq=tropics+MCS|title=Observations of surface to atmosphere interactions in the tropics|author=Michael Garstang, David Roy Fitzjarrald|pages=40–41|year=1999|isbn=978-0-19-511270-2|publisher=Oxford University Press US 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.cite web|author=B. Geerts|year=1998|url= http://www-das.uwyo.edu/~geerts/cwx/notes/chap10/lake_effect_snow.html|title=Lake Effect Snow|accessdate=2008-12-24|publisher= University of Wyoming Polar lows are a second special class of MCS. They form at high latitudes during the cold season.cite book|author=E. A. Rasmussen and J. Turner|year=2003|title=Polar Lows: Mesoscale Weather Systems in the Polar Regions|publisher=Cambridge University Press|page=612|isbn=978-0-521-62430-5 Once the parent MCS dies, later thunderstorm development can occur in connection with its remnant mesoscale convective vortex (MCV).cite web|title=3.5 The Influence of the Great Lakes on Warm Season Weather Systems During BAMEX|author=Lance F. Bosart and Thomas J. Galarneau, Jr.|url= http://ams.confex.com/ams/pdfpapers/84665.pdf|publisher=6th American Meteorological Society Coastal Meteorology Conference|year=2005|accessdate=2009-06-15 Mesoscale convective systems are important to the United States rainfall climatology over the Great Plains since they bring the region about half of their annual warm season rainfall.cite web|author=William R. Cotton, Susan van den Heever, and Israel Jirak|url= http://rams.atmos.colostate.edu/at540/fall03/fall03Pt9.pdf|title=Conceptual Models of Mesoscale Convective Systems: Part 9|date=Fall 2003|accessdate=2008-03-23
Motion
The two major ways thunderstorms move are via advection of the wind and propagation along outflow boundary|outflow boundaries towards sources of greater heat and moisture. Many thunderstorms move with the mean wind speed through the Earth's troposphere , or the lowest convert|8|km|mi of the Earth's atmosphere . Younger thunderstorms are steered by winds closer to the Earth's surface than more mature thunderstorms, as they are less 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) 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 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 a prominent feature and tracking it from scan to scan.
Back-building thunderstorm
A back building 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 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.cite web|url= http://www.srh.noaa.gov/jetstream/tstorms/tstrmtypes.htm|title=Types of Thunderstorms|author= National Weather Service JetStream|publisher= National Weather Service Southern Region Headquarters|date=2009-09-01|eeeate=2009-09-03 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 continuous, stationary cell that dropped an enormous quantity of rain, resulting in devastating flash flooding.cite web|url= http://www.crh.noaa.gov/unr/? n=weather|author= National Weather Service Forecast Office, Rapid City, South Dakota |title=The Rapid City Flood of 1972|publisher= National Weather Service Central Region Headquarters|accessdate=2009-09-03|date=2007-05-15 A similar event occurred in Boscastle , England, on 16 August 2004.cite web|url= http://www.tintagelweb.co.uk/BoscastleFlood.htm|title=Boscastle Flood 2004|author=David Flower|publisher=Tintagel – King Arthur Country|date=2008-02-09|accessdate=2009-09-03
Hazards
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 (season)|spring and summer , they can occur at just about any time of the year.
Cloud-to-ground lightning
See also|Acid rain|Lightning|Wildfire Lightning#Cloud-to-ground lightning|Cloud-to-ground lightning frequently occur within 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.Cite journal | doi =10.1016/S0031-0182(00)00192-9 | title =The Pre-Quaternary history of fire | year =2000 | author =Scott, A | journal =Palaeogeography Palaeoclimatology Palaeoecology | volume =164 | pages =281 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.Cite web|url= http://plaza.ufl.edu/rakov/Gas.html|title=Lightning Makes Glass|accessdate=November 7, 2007|publisher= University of Florida , Gainesville|year=1999|author=Vladimir A. Rakov Wildfires can devastate vegetation and the biodiversity of an ecosystem. Wildfires that occur close to urban environments can inflict damages upon infrastructures, buildings, crops, and provide risks to explosions, should the flames come in contact with gas pipes or tanks. Direct damage caused by lightning strikes occurs on occasion.cite web|url= http://www.hughston.com/hha/a_12_3_4.htm|title=Lightning and Its Hazards|author=Bruce Getz and Kelli Bowermeister|publisher=Hughston Sports Medicine Foundation|date=2009-01-09|accessdate=2009-09-09 In areas with a high frequency for cloud-to-ground lightning, like Florida , lightning causes several fatalities per year, most commonly to people working outside.cite web|url= http://ams.confex.com/ams/88Annual/techprogram/paper_132808.htm|title=P2.13 Florida lightning deaths and injuries 2004–2007|author=Charles H. Paxton, J. Colson and N. Carlisle|publisher= American Meteorological Society |year=2008|accessdate=2009-09-05
Precipitation with low PH|potential of hydrogen levels (pH), otherwise known as acid rain, is also a frequent risk produced by lightning. Distilled water , which contains no carbon dioxide , has a Neutral solution|neutral pH of 7. Liquids with a pH less than 7 are acidic, and those with a pH greater than 7 are bases. “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 , a weak acid (pH 5.6 in distilled water), but unpolluted rain also contains other chemicals.cite journal|author=G. E. Likens, W. C. Keene, J. M. Miller and J. N. Galloway|year=1987|title=Chemistry of precipitation from a remote, terrestrial site in Australia|journal=Journal of Geophysical Research|volume=92|issue=13|pages=299–314|bibcode = 1987JGR....92..299R |doi = 10.1029/JA092iA01p00299 Nitric oxide present during thunderstorm phenomena,cite journal|url= http://www.sciencedirect.com/science? _ob=ArticleURL& _udi=B757C-488FRK0-2N& _user=10& _rdoc=1& _fmt=& _orig=search& _sort=d& _docanchor=& view=c& _searchStrId=1001036955& _rerunOrigin=google& _acct=C000050221& _version=1& _urlVersion=0& _userid=10& md5=05e7b4ab4444bada8188d84c8a19ccc0|title=Tropospheric sources of NOx: Lightning and biology |author=Joel S. Levine, Tommy R. Augustsson, Iris C. Andersont, James M. Hoell Jr., and Dana A. Brewer|doi=10.1016/0004-6981(84)90355-X|journal=Atmospheric Environment|volume=18|issue=9|pages=1797–1804|year=1984|accessdate=2009-09-04|pmid=11540827 caused by the splitting of nitrogen molecules, 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 other solid chemical compounds containing carbon. 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.cite web|author=Office of Air and Radiation Clean Air Markets Division|url= http://www.epa.gov/acidrain/effects/surface_water.html|title=Effects of Acid Rain – Surface Waters and own Aquatic Animals|accessdate=2009-09-05|date=2008-12-01|publisher= United States Environmental Protection Agency
Large hailstones
Main|HailAny thunderstorm that produces hail that reaches the ground is known as a hailstorm.cite web|url= http://amsglossary.allenpress.com/glossary/search? p=1& query=Hailstorm|title=Hailstorm|author=Glossary of Meteorology|year=2009|accessdate=2009-08-29|publisher= American Meteorological Society 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 lift ing), thereby intensifying the updrafts within thunderstorms and making hail more likely.cite web|url= http://www.ga.gov.au/hazards/severeweather/where.jsp|title=Where does severe weather occur? |author=Geoscience Australia|publisher=Commonwealth of Australia|accessdate=2009-08-28|date=2007-09-04|archiveurl= http://web.archive.org/web/20090621231613/ http://www.ga.gov.au/hazards/severeweather/where.jsp |archivedate=2009-06-21 One of the more common regions for large hail is across the mountainous northern India , which reported one of the highest hail-related death tolls on record in 1888.cite book|url= http://books.google.com/? id=-mwbAsxpRr0C& pg=PA401& lpg=PA401& dq=hail+regions+with+most+deaths& q=hail%20regions%20with%20most%20deaths|title=Encyclopedia of World Climatology|author=John E. Oliver|page=401|publisher=Springer|isbn=978-1-4020-3264-6|year=2005|accessdate=2009-08-28 China also experiences significant hailstorms.cite journal|url= http://www.sciencedirect.com/science? _ob=ArticleURL& _udi=B6V95-4TF7C4P-4& _user=10& _rdoc=1& _fmt=& _orig=search& _sort=d& _docanchor=& view=c& _searchStrId=993864234& _rerunOrigin=google& _acct=C000050221& _version=1& _urlVersion=0& _userid=10& md5=bd935558a57c1193db56b67f4dfbb500|title=The characteristics of cloud-to-ground lightning activity in hailstorms over northern China |author=Dongxia Liu, Guili Feng, and Shujun Wu|date=February 2009|accessdate=2009-08-28|journal=Atmospheric Research|volume=91|issue=2–4|pages=459–465|doi=10.1016/j.atmosres.2008.06.016 Across Europe , Croatia experiences frequent occurrences of hail.cite journal|url= http://www.sciencedirect.com/science? _ob=ArticleURL& _udi=B6V95-4TSD9BB-1& _user=10& _rdoc=1& _fmt=& _orig=search& _sort=d& _docanchor=& view=c& _searchStrId=993917632& _rerunOrigin=google& _acct=C000050221& _version=1& _urlVersion=0& _userid=10& md5=266c74d3126cb095e4597efa6c2f5598|title=Hail characteristics of different regions in continental part of Croatia based on influence of orography|author=Damir Pocakal, Željko Vecenaj, and Janez Štalec|journal=Atmospheric Research|volume=93|issue=1–3|date=July 2009|doi=10.1016/j.atmosres.2008.10.017|pages=516
In North America , hail is most common in the area where Colorado , Nebraska , and Wyoming meet, known as "Hail Alley."cite web|url= http://www.ucar.edu/communications/factsheets/Hail.html|title=Fact Sheet on Hail|accessdate=2009-07-18|author=Rene Munoz|date=2000-06-02|publisher=University Corporation for Atmospheric Research Hail in this region occurs between the months of March and October during the afternoon and evening hours, with 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.
Hail can cause serious damage, notably to automobile s, aircraft, skylights, glass-roofed structures, livestock , and most commonly, farmers' crops .cite journal|url= http://www.cocorahs.org/media/docs/hail_1994.pdf|title=Hail, Hail, Hail & #33; The Summertime Hazard of Eastern Colorado|author=Nolan J. Doesken|journal=Colorado Climate|volume=17|issue=7|date=April 1994|accessdate=2009-07-18 Hail is one of the most significant thunderstorm hazards to aircraft. When hail stones exceed convert|0.5|in|mm|adj=1 in diameter, planes can be seriously damaged within seconds.cite web|url= http://www.aviationweather.ws/063_Hazards.php|title=Hazards|author= Federal Aviation Administration |year=2009|accessdate=2009-08-29 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.cite book|url= http://books.google.com/? id=s6oxEraqWWwC& pg=RA1-PA61& lpg=RA1-PA61& dq=causes+of+accumulating+hail+storms& q=hail|title=Introduction to international disaster management|author=Damon P. Coppola|page=62|year=2007|isbn=978-0-7506-7982-4|publisher=Butterworth-Heinemann Rarely have massive hailstones been known to cause concussion s or fatal head physical trauma|trauma . Hailstorms have been the cause of costly and deadly events throughout history. One of the earliest recorded incidents occurred around the 9th century in Roopkund , Uttarakhand , India .cite web|url= http://www.telegraph.co.uk/news/main.jhtml? xml=/news/2004/11/07/wind07.xml& sSheet=/news/2004/11/07/ixworld.html |title=Giant hail killed more than 200 in Himalayas|author=David Orr|date=2004-11-07|accessdate=2009-08-28|publisher=Telegraph Group Unlimited via the Internet Wayback Machine |archiveurl = http://web.archive.org/web/20051203015218/ http://www.telegraph.co.uk/news/main.jhtml? xml=/news/2004/11/07/wind07.xml& sSheet=/news/2004/11/07/ixworld.html |archivedate = 2005-12-03 The largest hailstone in terms of maximum circumference and length ever recorded in the United States fell in 2003 in Aurora, Nebraska , USA .C. A. Knight and N.C. Knight, 2005: Very Large Hailstones From Aurora, Nebraska. Bull. Amer. Meteor. Soc., 86, 1773–1781.
Tornadoes and waterspouts
Main|Tornado|WaterspoutA tornado is a violent, dangerous, rotating column of air in contact with both the surface of 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 Funnel cloud|condensation funnel , whose narrow end touches the earth and is often encircled by a cloud of debris and dust .cite journal |last = Renno |first = Nilton O. |title = A thermodynamically general theory for convective vortices |journal = Tellus A |volume = 60 |issue = 4 |pages = 688–99 |publisher = |month = August | year = 2008 |url = http://vortexengine.ca/misc/Renno_2008.pdf |format=PDF|doi = 10.1111/j.1600-0870.2008.00331.x |bibcode=2008TellA..60..688R Most tornadoes have wind speeds between convert|40|and|110|mph|km/h|abbr=on, are approximately convert|250|ft|m across, and travel a few miles (several kilometers) before dissipating. Some attain wind speeds of more than convert|300|mph|km/h|abbr=on, stretch more than convert/spell|1|mi|km across, and stay on the ground for dozens of miles (more than 100& nbsp;km).cite web| url = http://www.spc.noaa.gov/faq/tornado| title = The Online Tornado FAQ| accessdate = 2006-09-08| last = Edwards| first = Roger| date = 2006-04-04| publisher = Storm Prediction Center cite web| url = http://cswr.org/dow/DOW.htm| title = Doppler On Wheels| accessdate = 2006-12-29| publisher = http://cswr.org/ Center for Severe Weather Research| year = 2006cite web| url = http://www.crh.noaa.gov/oax/archive/hallam/hallam.php| title = Hallam Nebraska Tornado | accessdate = 2006-09-08| publisher = Omaha/Valley, NE Weather Forecast Office | date = 2005-10-02 The Fujita scale and the Enhanced Fujita Scale rate tornadoes by damage caused. An EF0 tornado, the weakest category, damages trees but not substantial structures. An EF5 tornado, the strongest category, rips buildings off their foundations and can deform large skyscraper s. The similar TORRO scale ranges from a T0 for extremely weak tornadoes to T11 for the most powerful known tornadoes.cite web|url= http://www.torro.org.uk/TORRO/ECSS_Slide_Show/2004%20SPAIN%20ECSS%20Post-FINAL%20slide%20show.html|title=Wind Scales: Beaufort, T – Scale, and Fujita's Scale|author=Dr. Terence Meaden|publisher=Tornado and Storm Research Organisation|year=2004|accessdate=2009-09-11 Pulse-Doppler radar|Doppler weather radar|radar data, photogrammetry , and ground swirl patterns (cycloidal marks) may also be analyzed to determine intensity and award a rating.cite web | title = Enhanced F Scale for Tornado Damage| author = Storm Prediction Center| publisher= National Oceanic and Atmospheric Administration | url = http://www.spc.noaa.gov/efscale/ef-scale.html| accessdate = 2009-06-21
Waterspouts have similar characteristics as tornadoes, characterized by a spiraling funnel-shaped wind current that form over bodies of water, connecting to large Cumlonimbus clouds. Waterspouts are generally classified as forms of tornadoes, or more specifically, non- supercell ed tornadoes that develop over large bodies of water.cite web|url= http://amsglossary.allenpress.com/glossary/search? p=1& query=Waterspout|title=Waterspout|year=2009|accessdate=2009-09-11|publisher= American Meteorological Society These spiralling columns of air are frequently developed within tropical areas close to the equator , but are less common within areas of high latitude .cite web|url= http://www.erh.noaa.gov/btv/events/15Jan2009/overview.shtml|title=15 January 2009: Lake Champlain Sea Smoke, Steam Devils, and Waterspout: Chapters IV and V|author= National Weather Service Forecast Office, Burlington, Vermont |publisher=Eastern Region Headquarters|date=2009-02-03|accessdate=2009-06-21
Flash flood
Main|Flash floodFlash flooding is the process where a landscape, most notably an urban environment, is subjected to rapid floods.cite web|url= http://amsglossary.allenpress.com/glossary/search? p=1& query=Flash+flood|title=Flash Flood|author=Glossary of Meteorology|publisher= American Meteorological Society |year=2009|accessdate=2009-09-09 These rapid floods occur more quickly and are more localized than seasonal river flooding or areal floodingcite web|last=National Weather Service|title=Flood Products: What Do They Mean? |url= http://www.srh.noaa.gov/bmx/? n=outreach_flw|publisher=NOAA|accessdate=23 August 2011 and are frequently (though not always) associated with intense rainfall.cite web|last=National Weather Service|title=Flash Flood|url= http://www.crh.noaa.gov/glossary.php? word=FLASH%20FLOOD|publisher=NOAA|accessdate=23 August 2011 Flash flooding can frequently occur in slow-moving thunderstorms and is usually caused by the heavy liquid precipitation that accompanies it. Flash floods are most common in densely populated urban environments, where few plants and bodies of water are presented 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 the force of raging water. Automobiles parked within experiencing areas can also be displaced. Soil erosion can occur as well, exposing risks of landslide phenomena.
Downburst
Main|DownburstDownburst 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,cite web|url= http://www.erh.noaa.gov/cae/svrwx/downburst.htm|title=Downbursts...|date=2009-01-27|author= National Weather Service Forecast Office Columbia, South Carolina |publisher= National Weather Service Eastern Region Headquarters|accessdate=2009-09-09 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 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.
Safety precautions
See also|Emergency management|Tornado preparedness Most thunderstorms come and go fairly uneventfully; however, any thunderstorm can become severe, and all thunderstorms, by definition, present the danger of lightning.cite web|last=American Red Cross|title=Thunderstorm Safety Checklist|url= http://www.redcross.org/www-files/Documents/pdf/Preparedness/checklists/Thunderstorm.pdf|publisher=American Red Cross|accessdate=24 August 2011 Thunderstorm preparedness and safety refers to taking steps before, during, and after a thunderstorm to minimize injury and damage.
Preparedness
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).cite web|last=National Weather Service Weather Forecast Office|title=Thunderstorm|url= http://www.srh.noaa.gov/abq/? n=prepthunderstorms|work=Severe Weather Preparedness Information|publisher=NOAA|accessdate=24 August 2011|location=Albuquerque, NM Preparing a family emergency plan, for example, can save valuable time if a storm arises quickly and unexpectedly.cite web|last=Federal Emergency Management Agency|title=Thunderstorms and Lightning|url= http://www.ready.gov/america/beinformed/thunderstorms.html|work=Ready|publisher=US Department of Homeland Security|accessdate=24 August 2011|archiveurl= http://web.archive.org/web/20110623092608/ http://www.ready.gov/america/beinformed/thunderstorms.html |archivedate=23 June 2011 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.cite web|last=Federal Emergency Management Agency|title=What to Do Before a Thunderstorm|url= http://www.fema.gov/hazard/thunderstorm/th_before.shtm|publisher=US Department of Homeland Security|accessdate=24 August 2011
The National Weather Service in the United States recommends several precautions that people should take if thunderstorms are likely to occur: :* People should know the names of local counties, cities, and towns, as these are how warnings are described. :* Monitor forecasts and know whether thunderstorms are likely in the area. :* Be alert for natural signs of an approaching storm. :* Cancel or reschedule outdoor events (to avoid being caught outdoors when a storm hits). :* Avoid open areas like hilltops, fields, and beaches.
Safety
While safety and preparedness often overlap, “thunderstorm safety” generally refers to what people should do during and after a storm. The American Red Cross recommends that people follow these precautions if a storm is imminent or in progress:
:*Take action immediately upon hearing thunder. Anyone close enough to the storm to hear thunder can be struck by lightning. :*Avoid electrical appliances, including corded telephones. Cordless and wireless telephones are safe to use during a thunderstorm. :* Close and stay away from windows and doors, as glass can become a serious hazard in high wind. :* Do not bathe or shower, as plumbing conducts electricity. :* If driving, safely exit the roadway, turn on hazard lights, and park. Remain in the vehicle and avoid touching metal. :* If reaching a safe, sturdy building is not possible, crouch as low as possible (in a low area like a ditch) and minimize contact with the ground.
Frequent occurrences
See also|United States rainfall climatology Thunderstorms occur throughout the world, even in the polar regions, with the greatest frequency in tropical rainforest areas, where they may occur nearly daily. Kampala and Tororo in Uganda have each been mentioned as the most thunderous places on Earth,cite web | url = http://sky-fire.tv/index.cgi/thunderstorms.html#occur | title = How many thunderstorms occur each year? | work = Thunderstorms | publisher = Sky Fire Productions | accessdate = 2006-08-23 a claim also made for Bogor on Java (island)|Java , Indonesia and Singapore . Thunderstorms are associated with the various monsoon seasons around the globe, and they populate the rainband s of tropical cyclone s.cite web|url= http://www.srh.noaa.gov/jetstream/tropics/tc_hazards.htm|title=Tropical Cyclone Hazards|accessdate=2009-08-30|date=2008-10-08|author= National Weather Service JetStream|publisher= National Weather Service Southern Region Headquarters In temperate regions, they are most frequent in spring and summer, although they can occur along or ahead of cold front s at any time of year.cite web|author=David Roth|title=Unified Surface Analysis Manual|accessdate=2006-10-22|publisher= Hydrometeorological Prediction Center |url= http://www.hpc.ncep.noaa.gov/sfc/UASfcManualVersion1.pdf 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 the most powerful thunderstorms over the United States occur in the Midwest and the Southern United States|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 ,cite web |url= http://www.ofcm.gov/slso/pdf/slsochp2.pdf |title=National Severe Local Storms Operations Plan – Chapter 2 |format=PDF |author=Office of the Federal Coordinator for Meteorology|publisher= Department of Commerce |date=2001-06-07|accessdate=2006-08-23 but they occur with greater frequency in the inland areas, particularly the Sacramento Valley|Sacramento and San Joaquin Valley|San Joaquin Valleys of California . In spring and summer, they occur nearly daily in certain areas of the Rocky Mountains as part of the North American Monsoon regime. In the Northeastern United States|Northeast , storms take on similar characteristics and patterns as the Midwest, only less frequently and severely. During the summer, air-mass thunderstorm s are an almost daily occurrence over central and southern parts of Florida .
Types of lightning
main|Lightning Lightning is an electrical discharge that occurs in a thunderstorm. It can be seen in the form of a bright streak (or bolt) from the sky. Lightning occurs when an electrical charge is built up within a cloud, due to static electricity generated by supercooling|supercooled water droplet s colliding with ice crystal s near the freezing level . When a large enough charge is built up, a large discharge will occur and can be seen as lightning.
The temperature of a lightning bolt can be five times hotter than the surface of the sun.cite web | title = Lightning | publisher = BBC | author=Bill Giles O.B.E | date=2004-09-01| url = http://www.bbc.co.uk/weather/features/understanding/lightning.shtml | accessdate = 2008-06-29 Dead link|date=April 2012|bot=H3llBot Although the lightning is extremely hot, the duration is short and 90% of strike victims survive. Contrary to the popular idea that lightning does not strike twice in the same spot, some people have been struck by lightning over three times, and skyscrapers like the Empire State Building have been struck numerous times in the same storm.cite web|url= http://www.nasa.gov/centers/goddard/news/topstory/2003/0107lightning.html|title=Lightning really does hit more than twice|author= Goddard Space Flight Center |publisher= National Aeronautics and Space Administration |date=2003-01-14|accessdate=2009-09-09 The loud bang that is heard is the super heated air around the lightning bolt expanding at the speed of sound . Because sound travels much more slowly than light the flash is seen before the bang, although both occur at the same moment.
There are several types of lightning:
In-cloud lightning is the most common. It is lightning within a cloud and is sometimes called intra-cloud or sheet lightning.
Cloud to ground lightning is when a bolt of lightning from a cloud strikes the ground. This form poses the greatest threat to life and property.
Ground to cloud lightning is when a lightning bolt is induced from the ground to the cloud.
Cloud to cloud lightning is rarely seen and is when a bolt of lightning arcs from one cloud to another.
Ball lightning is extremely rare and has several hypothesized explanations. It is seen in the form of a 15 to 50 centimeter radius ball.cite web|url= http://amsglossary.allenpress.com/glossary/search? p=1& query=Ball+lightning|title=Ball Lightning|author=Glossary of Meteorology|publisher= American Meteorological Society |year=2009|accessdate=2009-09-09
Cloud to air lightning is when lightning from a cloud hits air of a different charge.cite web|url= http://amsglossary.allenpress.com/glossary/search? id=lightning1|title=Lightning|author=Glossary of Meteorology|publisher= American Meteorological Society |year=2009|accessdate=2009-09-09
Dry lightning is a misnomer that refers to a thunderstorm whose precipitation does not reach the ground.
Heat Lightning refers to a lightning flash that is seen from the horizon that does not have accompanying thunder.cite web|author=Glossary of Meteorology|url= http://amsglossary.allenpress.com/glossary/search? p=1& query=heat+lightning& submit=Search|title=Heat Lightning|year=2009|publisher= American Meteorological Society |accessdate=2009-09-09
Upper-atmospheric lightning occurs above the thunderhead.
Energy
see also|Sprite (lightning)|Upper-atmospheric lightning|St. Elmo's fireIf the quantity of water that is condensed in and subsequently precipitated from a cloud is known, then the total energy of a thunderstorm can be calculated. In a typical thunderstorm, approximately 5×108 kilograms|kg of water vapor are lifted, and the amount of energy released when this condenses is 1015 joules . This is on the same order of magnitude of energy released within a tropical cyclone, and more energy than that released during Atomic bombings of Hiroshima and Nagasaki|the atomic bomb blast at Hiroshima, Japan in 1945 .
The Fermi Gamma-ray Burst Monitor results show that gamma ray s and antimatter particles ( positron s) can be generated in powerful thunderstorms. http://www.nasa.gov/mission_pages/GLAST/news/fermi-thunderstorms.html It is suggested that the antimatter positrons are formed in terrestrial gamma-ray flash es (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.cite news|last=Ouellette|first=Jennifer|title=Fermi Spots Antimatter in Thunderstorms|url= http://news.discovery.com/space/fermi-spots-antimatter-in-thunderstorms.html|accessdate=16 January 2011|newspaper=Discovery News|date=January 13, 2011 About 500 TGFs may occur every day worldwide, but mostly go undetected.
Studies
In more contemporary times, thunderstorms have taken on the role of a scientific curiosity. Every spring, storm chasing|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.cite web|url= http://www.cimms.ou.edu/~stumpf/cethics.html|title=Storm Chase Ethics|author=Alan Moller|date=2003-03-05|accessdate=2009-09-09 Radio pulses produced by cosmic rays are being used to study how electric charges develop within thunderstorms.cite web|url= http://www.spaceref.com/news/viewpr.html? pid=28329|title=Scientists use high-energy particles from space to probe thunderstorms|date=2009-06-02|accessdate=2009-09-09|author= Florida Institute of Technology More organized meteorological projects such as VORTEX projects#VORTEX2|VORTEX2 use an array of sensors, such as the Doppler on Wheels , vehicles with mounted automated weather station s, weather balloon s, and unmanned aircraft to investigate thunderstorms expected to produce severe weather.cite web|url= http://www.vortex2.org/home/|title=What is VORTEX2? |author=VORTEX2|year=2009|accessdate=2009-09-09Lightning is detected remotely using sensors that detect cloud-to-ground lightning strokes with 95& nbsp;percent accuracy in detection and within convert|250|m|ft of their point of origin.cite web|url= http://ams.confex.com/ams/89annual/techprogram/paper_149149.htm|title=An Overview of the United States Precision Lightning Network (USPLN)|author=Peter P. Neilley and R. B. Bent|publisher= American Meteorological Society Fourth Conference on the Meteorological Applications of Lightning Data|year=2009|accessdate=2009-09-09
Mythology
Thunderstorms strongly influenced many early civilizations. Ancient Greece|Greeks thought they were battles waged by Zeus , who hurled lightning bolts forged by Hephaestus . Some Indigenous peoples of the Americas|American Indian tribes associated thunderstorms with the Thunderbird (mythology)|Thunderbird , who they believed was a servant of the Great Spirit .cite web|url= http://web.raex.com/~obsidian/HaudPan.html|title=A Haudenosaunee Pantheon|date=2008-06-11|accessdate=2009-09-09|author=Obsidian's Lair|publisher=Corecomm The Norsemen|Norse considered thunderstorms to occur when Thor went to beat on Jötnar , with the thunder and lightning being the effect of his strikes with the hammer Mjölnir . Christianity|Christian doctrine accepted the ideas of Aristotle 's original work, called Meteorology (Aristotle)|Meteorologica , that winds were caused by exhalations from the Earth and that fierce storms were the work of God . These ideas were still within the mainstream as late as the 18th century.cite book|author=John D. Cox|title=Storm Watchers|page=7|isbn=0-471-38108-X|year=2002|publisher=John Wiley & Sons, Inc.
Outside of Earth
The clouds of Venus are capable of producing lightning much like the clouds on Earth. The lightning rate is at least half of that on Earth.cite journal | last=Russell | first=S. T. | coauthors=Zhang, T.L.; Delva, M.; et al. | title=Lightning on Venus inferred from whistler-mode waves in the ionosphere | journal=Nature | year=2007 | volume=450 | pages=661–662 | doi=10.1038/nature05930 | pmid=18046401 | issue=7170 | bibcode=2007Natur.450..661R A thin layer of Water (properties)|water clouds appears to underlie the ammonia layer within Jupiter 's atmosphere, where thunderstorms evidenced by flashes of lightning have been detected. (Water is a polar molecule that can carry a charge, so it is capable of creating the charge separation needed to produce lightning.)cite book |first=Linda T.|last=Elkins-Tanton|year=2006 |title=Jupiter and Saturn|publisher=Chelsea House |location=New York|isbn=0-8160-5196-8 These electrical discharges can be up to a thousand times as powerful as lightning on the Earth.cite web |editor=Watanabe, Susan|date = February 25, 2006 |url = http://www.nasa.gov/vision/universe/solarsystem/galileo_end.html |title = Surprising Jupiter: Busy Galileo spacecraft showed jovian system is full of surprises |publisher = NASA|accessdate = 2007-02-20 The water clouds can form thunderstorms driven by the heat rising from the interior.cite journal |last = Kerr|first = Richard A. |title=Deep, Moist Heat Drives Jovian Weather |journal=Science|year=2000|volume=287|issue=5455 |pages=946–947 |url= http://www.sciencemag.org/cgi/content/full/287/5455/946b |doi=10.1126/science.287.5455.946b |accessdate = 2007-02-24
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External links
Commons|Thunderstorm
http://www.thunderstorm.se Thunderstorm lightning in realtime – Europe
http://www.canadiangeographic.ca/atlas/themes.aspx? id=weather& sub=weather_phenomena_thunderstorm& lang=En Anatomy of a thunderstorm
http://www.ejssm.org/ Electronic Journal of Severe Storms Meteorology
http://www.economics.noaa.gov/? goal=weather& file=events/storm/ Social & Economic Costs of Thunderstorms & High Winds NOAA Economics
http://www.wetter-foto.de/fotos-5-1-all-Gewitterwolken.html Thunderstorm photography in Germany
Meteorological variables Good article Category:Atmospheric electricity Category:Weather hazards to aircraft Category:Microscale meteorology Category:Severe weather and convection Category:Storm Category:Weather hazards