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'''Orkan''' ili '''uragan''' je [[meteorologija|meteorološka]] pojava na [[Zemlja|Zemlji]] koja se sastoji od brzih [[vjetar|vjetrova]] te mnogo [[kiša|kiše]]. Uragani mogu trajati nekoliko dana ili tjedana i česta su pojava na istoku [[SAD]], Jugoistočnoj [[Azija|Aziji]] i na sjeveru [[Australija|Australije]]. Suprotno o medijskim napisima o snažnim vjetrovima koji sve uništavaju na svom putu uragani su na kopnu mnogo slabiji vjetar od naše bure iako u obalnom području imaju veću razornu moć zbog dizanja razine mora [http://blog.meteoadriatic.net/2012/10/30/tc-sandy-vs-jadranska-bura/].
[[File:Hurricane Isabel from ISS.jpg|right|300px|thumb|[[Uragan Izabela]] (2003) snimljen iz orbite tokom [[Ekspedicija 7|Ekspedicije 7]] na [[Međunarodna svemirska stanica|Međunarodnoj svemirskoj stanici]]. [[Oko (ciklon)|Oko]], zid oka, i okružujući kišni opsezi, karakteristični za tropske [[ciklon]]e, su jasno vidljivi u ovom pogledu iz svemira.]] {{Weather}}
 
'''Orkan''' (''tropski ciklon'', ''uragan'') [[meteorologija|meteorološka]] je pojava na [[Zemlja|Zemlji]] koja se sastoji od brzih [[vjetar|vjetrova]] te mnogo [[kiša|kiše]]. Uragani mogu trajati nekoliko dana ili tjedana i česta su pojava na istoku [[SAD]], Jugoistočnoj [[Azija|Aziji]] i na sjeveru [[Australija|Australije]]. Suprotno o medijskim napisima o snažnim vjetrovima koji sve uništavaju na svom putu uragani su na kopnu mnogo slabiji vjetar od naše bure iako u obalnom području imaju veću razornu moć zbog dizanja razine mora.<ref>[http://blog.meteoadriatic.net/2012/10/30/tc-sandy-vs-jadranska-bura/ TC Sandy vs jadranska bura]</ref>
Sezona uragana u [[SAD]] traje od [[1.6.|1. juna]] do [[30.11|30. novembra]].
== Work in progress ==
Tropski ciklon je brzo rotirajući [[oluja|olujni sitem]] koji se odlikuje [[high pressure system|low-pressure]] center, [[Beaufort scale|strong winds]], and a spiral arrangement of [[thunderstorm]]s that produce heavy rain. Depending on its location and strength, a tropical cyclone is referred to by names such as [[#Hurricane or typhoon|hurricane]] ({{IPAc-en|ˈ|h|ʌr|ɨ|k|ən}} or {{IPAc-en|ˈ|h|ʌr|ɨ|k|eɪ|n}}<ref>{{cite web|url=http://www.oxforddictionaries.com/us/definition/english/hurricane#hurricane|title=hurricane|publisher=Oxford dictionary |accessdate=October 1, 2014}}</ref><ref>{{cite web|url=http://www.merriam-webster.com/dictionary/hurricane|title=Hurricane - Definition and More from the Free Merriam-Webster Dictionary|accessdate=October 1, 2014}}</ref><ref>{{cite web|url=http://www.collinsdictionary.com/dictionary/english/hurricane|title=Definition of "hurricane" - Collins English Dictionary|accessdate=October 1, 2014}}</ref>), [[#Hurricane or typhoon|typhoon]] {{IPAc-en|t|aɪ|'|f|uː|n}}, [[#Tropical storm|tropical storm]], cyclonic storm, [[#Tropical depression|tropical depression]], and simply cyclone.<ref>{{cite web|url=http://oceanservice.noaa.gov/facts/cyclone.html|title=The only difference between a hurricane, a cyclone, and a typhoon is the location where the storm occurs|publisher=noaa.gov|accessdate=October 1, 2014}}</ref>
 
Tropical cyclones typically form over large bodies of relatively warm water. They derive their energy through the evaporation of [[water]] from the [[ocean]] surface, which ultimately [[condensation|recondenses]] into [[clouds]] and rain when moist air rises and cools to [[Saturated fluid|saturation]]. This [[energy source]] differs from that of [[extratropical cyclone|mid-latitude cyclonic storms]], such as [[nor'easter]]s and [[European windstorm]]s, which are fueled primarily by [[Baroclinic instability|horizontal temperature contrasts]]. The strong rotating winds of a tropical cyclone are a result of the [[conservation of angular momentum]] imparted by the Earth's rotation as air flows inwards toward the axis of rotation. As a result, they rarely form within 5° of the equator.<ref name="BAMS Zhang 1988">{{cite doi|10.1175/1520-0477(1998)079<0019:TCAGCC>2.0.CO;2}}</ref> Tropical cyclones are typically between {{convert|100|and|4000|km|mi|abbr=on}} in diameter.
Formiraju se u [[Meksički zaliv|Meksičkom zalivu]] a onda različitom žestinom pogađaju jugoistočni deo Sjedinjenih Američkih Država ali i [[karibi|karibske]] zemlje..
 
''Tropical'' refers to the geographical origin of these systems, which form almost exclusively over [[tropics|tropical]] seas. ''Cyclone'' refers to their cyclonic nature, with wind blowing [[Clockwise and counterclockwise|counterclockwise]] in the [[Northern Hemisphere]] and clockwise in the [[Southern Hemisphere]]. The opposite direction of circulation is due to the [[Coriolis effect]].
Uragani imaju često veoma teške posledice - vidi [[Uragan Katrina]]. Zbog čestih i katastrofalnih posledica formirana je i američka baza za [[okean]]ska i atmosferska osmatranja, koja primenom savremenih tehnologija osmatra i upozorava stanovništvo.
 
In addition to strong winds and rain, tropical cyclones are capable of generating high waves, damaging [[storm surge]], and [[tornado]]es. They typically weaken rapidly over land where they are cut off from their primary energy source. For this reason, coastal regions are particularly vulnerable to damage from a tropical cyclone as compared to inland regions. Heavy rains, however, can cause significant flooding inland, and storm surges can produce extensive coastal [[flood]]ing up to {{convert|40|km|mi}} from the coastline. Though their effects on human populations are often devastating, tropical cyclones can relieve [[drought]] conditions. They also carry heat energy away from the tropics and transport it toward [[temperate]] [[latitudes]], which may play an important role in modulating regional and global [[climate]].
Sasvim je uobičajena pojava da se i više stotina hiljada ljudi privremeno iseljava iz oblasti kojima preti uragan.
 
== Fizička struktura ==
{{See also|Oko (ciklon)}}
[[File:Typhooon Nabi as seen from the ISS.jpg|thumb|left|300px|[[Typhoon Nabi]] as seen from the [[International Space Station]], on September 3, 2005. ]]
 
Tropical cyclones are areas of relatively [[Low-pressure area|low pressure]] in the [[troposphere]], with the largest pressure perturbations occurring at low altitudes near the surface. On Earth, the pressures recorded at the centres of tropical cyclones are among the lowest ever observed at [[sea level]].<ref name="ABC pressures">{{cite news|author=Symonds, Steve|title=Highs and Lows|work=Wild Weather|url=http://www.abc.net.au/northcoast/stories/s989385.htm|publisher= Australian Broadcasting Corporation |date=November 17, 2003|accessdate=March 23, 2007|archiveurl = http://web.archive.org/web/20071011194541/http://www.abc.net.au/northcoast/stories/s989385.htm |archivedate = October 11, 2007|deadurl=yes}}</ref> The environment near the center of tropical cyclones is warmer than the surroundings at all altitudes, thus they are characterized as "warm core" systems.<ref name="AOML FAQ A7">{{cite web|title=Frequently Asked Questions: What is an extra-tropical cyclone?|publisher= National Oceanic and Atmospheric Administration |accessdate=March 23, 2007|url=http://www.aoml.noaa.gov/hrd/tcfaq/A7.html|author1 = Atlantic Oceanographic and Meteorological Laboratory|author2 = Hurricane Research Division|authorlink1= }}</ref>
 
=== Polje vetra ===
The near-surface wind field of a tropical cyclone is characterised by air rotating rapidly around a [[Eye (cyclone)|centre of circulation]] while also flowing radially inwards. At the outer edge of the storm, air may be nearly calm; however, due to the Earth's rotation, the air has non-zero [[absolute angular momentum]]. As air flows radially inward, it begins to [[cyclonic rotation|rotate cyclonically]] (counter-clockwise in the Northern Hemisphere, and clockwise in the Southern Hemisphere) in order to [[conservation of angular momentum|conserve angular momentum]]. At an inner radius, air begins to ascend to the [[tropopause|top of the troposphere]]. This radius is typically coincident with the inner radius of the [[eyewall]], and has the strongest near-surface winds of the storm; consequently, it is known as the ''[[radius of maximum wind]]s''.<ref name="NHC glossary">{{cite web|author= National Hurricane Center |url=http://www.nhc.noaa.gov/aboutgloss.shtml|year=2005|title=Glossary of NHC/TPC Terms|accessdate=November 29, 2006|publisher=[[National Oceanic and Atmospheric Administration]]}}</ref> Once aloft, air flows away from the storm's center, producing a shield of [[cirrus cloud]]s.<ref name="cirrus">{{cite web|title=Cirrus Cloud Detection|location=Monterey, CA|url=http://www.nrlmry.navy.mil/sat_training/nexsat/cirrus/NexSat_Cirrus.pdf|author=Marine Meteorology Division|work=Satellite Product Tutorials|publisher= United States Naval Research Laboratory |accessdate=June 4, 2013|format=PDF|page=1}}</ref>
 
The previously mentioned processes result in a wind field that is nearly [[axisymmetric]]: Wind speeds are low at the centre, increase rapidly moving outwards to the radius of maximum winds, and then decay more gradually with radius to large radii. However, the wind field often exhibits additional spatial and temporal variability due to the effects of localized processes, such as [[atmospheric convection|thunderstorm activity]] and horizontal [[Instability#Fluid instabilities|flow instabilities]]. In the vertical direction, winds are strongest near the surface and decay with height within the troposphere.<ref name="MWR Frank 1977">{{cite journal|author=Frank, W. M. |title=The structure and energetics of the tropical cyclone I. Storm structure|year=1977|journal= Monthly Weather Review |volume=105|issue=9|pages=1119–1135|bibcode = 1977MWRv..105.1119F |doi = 10.1175/1520-0493(1977)105<1119:TSAEOT>2.0.CO;2 }}</ref>
 
=== Oko i centar ===
[[File:Hurricane-en.svg|thumb|left|300px|Diagram of a Northern hemisphere hurricane.]]
[[File:HurrArthur720p.webm|right|left|300px|HurrArthur720p|NASA animation of Hurricane Arthur in 2014 showing rain rates and internal structure from [[Global Precipitation Measurement|GPM]] satellite data]]
At the center of a mature tropical cyclone, air sinks rather than rises. For a sufficiently strong storm, air may sink over a layer deep enough to suppress cloud formation, thereby creating a clear "[[Eye (cyclone)|eye]]". Weather in the eye is normally calm and free of clouds, although the sea may be extremely violent.<ref name="JetStream structure">{{cite web|url=http://www.srh.noaa.gov/jetstream/tropics/tc_structure.htm|author= National Weather Service |work=JetStream&nbsp;— An Online School for Weather|publisher= National Oceanic & Atmospheric Administration |title=Tropical Cyclone Structure|accessdate=May 7, 2009|date=October 19, 2005}}</ref> The eye is normally circular in shape, and is typically {{convert|30|–|65|km|mi|abbr=on}} in diameter, though eyes as small as {{convert|3|km|mi|abbr=on}} and as large as {{convert|370|km|mi|abbr=on}} have been observed.<ref name="WilmaTCR">{{cite web|last=Pasch|first=Richard J.|author2=Eric S. Blake, Hugh D. Cobb III, and David P. Roberts|url=http://www.nhc.noaa.gov/pdf/TCR-AL252005_Wilma.pdf|format=PDF|title=Tropical Cyclone Report: Hurricane Wilma: 15–25 October 2005|publisher= National Hurricane Center |date=September 28, 2006|accessdate=December 14, 2006}}</ref><ref name="MWR Lander 1999">{{cite doi|10.1175/1520-0493(1999)127<0137:ATCWAV>2.0.CO;2}}</ref>
 
The cloudy outer edge of the eye is called the "[[Eye (cyclone)|eyewall]]". The eyewall typically expands outward with height, resembling an arena football stadium; this phenomenon is sometimes referred to as the ''[[Eye (cyclone)#Stadium effect|stadium effect]]''.<ref name="MWR 1996 AHS summary">{{cite doi|10.1175/1520-0493(1999)127<0581:AHSO>2.0.CO;2 }}</ref> The [[eyewall]] is where the greatest wind speeds are found, air rises most rapidly, clouds reach to their highest altitude, and precipitation is the heaviest. The heaviest wind damage occurs where a tropical cyclone's eyewall passes over land.<ref name="JetStream structure"/>
 
In a weaker storm, the eye may be obscured by the [[central dense overcast]], which is the upper-level cirrus shield that is associated with a concentrated area of strong thunderstorm activity near the center of a tropical cyclone.<ref name="CDO AMS">{{cite web|author= American Meteorological Society |url=http://amsglossary.allenpress.com/glossary/browse?s=c&p=19|title=AMS Glossary: C|work=Glossary of Meteorology|accessdate=December 14, 2006|publisher= Allen Press }}</ref>
 
The eyewall may vary over time in the form of [[Eye (cyclone)#Eyewall replacement cycles|eyewall replacement cycles]], particularly in intense tropical cyclones. [[Rainbands|Outer rainbands]] can organize into an outer ring of thunderstorms that slowly moves inward, which is believed to rob the primary eyewall of moisture and [[angular momentum]]. When the primary eyewall weakens, the tropical cyclone weakens temporarily. The outer eyewall eventually replaces the primary one at the end of the cycle, at which time the storm may return to its original intensity.<ref name="AOML FAQ D8">{{cite web|author=Atlantic Oceanographic and Hurricane Research Division | title = Frequently Asked Questions: What are "concentric eyewall cycles" (or "eyewall replacement cycles") and why do they cause a hurricane's maximum winds to weaken?|publisher= National Oceanic and Atmospheric Administration |accessdate=December 14, 2006|url=http://www.aoml.noaa.gov/hrd/tcfaq/D8.html}}</ref>
 
=== Intenzitet ===
Storm "intensity" is defined as the maximum wind speed in the storm. This speed is taken as either a 1-minute or a 10-minute average at the standard reference height of 10 meters. The choice of averaging period, as well as the naming convention for classifying storms, [[Tropical cyclone scales|differs across forecast centers and ocean basins]].
 
=== Razmere ===
{|class="wikitable" style="float: right; font-size: 92%; margin: 1em 0 1em 1em;"
|-
! colspan=2 style="background: #ccf;" | Size descriptions of tropical cyclones
|-
! ROCI || Type
|-
| Less than 2&nbsp;degrees latitude || Very small/midget
|-
| 2 to 3&nbsp;degrees of latitude || Small
|-
| 3 to 6&nbsp;degrees of latitude || Medium/Average
|-
| 6 to 8&nbsp;degrees of latitude || Large
|-
| Over 8&nbsp;degrees of latitude || Very large<ref name="JTWCsize">{{cite web|url=http://www.usno.navy.mil/JTWC/frequently-asked-questions-1#tcsize|title=Q: What is the average size of a tropical cyclone?|year=2009|publisher= Joint Typhoon Warning Center |accessdate=May 7, 2009}}</ref>
|}
There are a variety of metrics commonly used to measure storm size. The most common metrics include the radius of maximum wind, the radius of 34-knot wind (i.e. [[Gale|gale force]]), the radius of outermost closed [[isobar (meteorology)|isobar]] ([[Radius of outermost closed isobar|ROCI]]), and the radius of vanishing wind.<ref name="Global">{{cite web|url=http://www.cawcr.gov.au/publications/BMRC_archive/tcguide/ch2/ch2_4.htm|title=Global Guide to Tropical Cyclone Forecasting: chapter 2: Tropical Cyclone Structure|date=May 7, 2009|publisher= Bureau of Meteorology |accessdate=May 6, 2009}}</ref><ref name="Chavas Emanuel GRL">{{cite doi|10.1029/2010GL044558}}</ref> An additional metric is the radius at which the cyclone's relative [[vorticity]] field decreases to 1×10<sup>−5</sup> s<sup>−1</sup>.<ref name="Liu / Chan AMS">{{cite doi|10.1175/1520-0493(1999)127<2992:SOTCAI>2.0.CO;2 }}</ref>
 
On Earth, tropical cyclones span a large range of sizes, from 100–2000&nbsp;km as measured by the radius of vanishing wind. They are largest on average in the northwest Pacific Ocean basin and smallest in the eastern Pacific Ocean basin. If the radius of outermost closed isobar is less than two [[latitude|degrees of latitude]] ({{convert|222|km|mi|abbr=on}}), then the cyclone is "very small" or a "midget". A radius of 3–6&nbsp;latitude degrees ({{convert|333|–|670|km|mi|abbr=on}}) is considered "average sized". "Very large" tropical cyclones have a radius of greater than 8&nbsp;degrees ({{convert|888|km|mi|abbr=on}}).<ref name="JTWCsize"/> Observations indicate that size is only weakly correlated to variables such as storm intensity (i.e. maximum wind speed), radius of maximum wind, latitude, and [[maximum potential intensity]].<ref name="Chavas Emanuel GRL" /><ref name="Merrill">{{Cite journal|title=A comparison of Large and Small Tropical cyclones|journal=Monthly Weather Review|volume=112|issue=7|pages=1408|last=Merrill|first=Robert T|date=1984|publisher= American Meteorological Society |doi=10.1175/1520-0493(1984)112<1408:ACOLAS>2.0.CO;2}}</ref>
 
Size plays an important role in modulating damage caused by a storm. All else equal, a larger storm will impact a larger area for a longer period of time. Additionally, a larger near-surface wind field can generate higher [[storm surge]] due to the combination of longer wind [[fetch (geography)|fetch]], longer duration, and enhanced [[wave setup]].<ref name="Irish et al JPO">{{cite doi|10.1175/2008JPO3727.1}}</ref> For example, [[Hurricane Sandy]], which struck the eastern U.S. in 2012, barely attained [[Saffir–Simpson hurricane wind scale|hurricane intensity]] prior to landfall yet was one of the [[List of costliest Atlantic hurricanes|costliest landfalling hurricanes]] in U.S. history because of its extremely large size.
 
The upper circulation of strong hurricanes extends into the [[tropopause]] of the atmosphere, which at low latitudes is {{convert|50000|-|60000|ft|order=flip}}.<ref name="Waco 1970">{{cite doi|10.1175/1520-0493(1970)098<0749:TATATL>2.3.CO;2 }}</ref>
 
== Fizika i energetika ==
[[File:Hurricane profile.svg|thumb|250px|right|Tropical cyclones exhibit an overturning circulation where air inflows at low levels near the surface, rises in thunderstorm clouds, and outflows at high levels near the tropopause.<ref>{{cite web|url=http://wind.mit.edu/~emanuel/anthro2.htm|title=Anthropogenic Effects on Tropical Cyclone Activity.|author=Emanuel, Kerry |date=February 8, 2006|publisher=Massachusetts Institute of Technology|accessdate=May 7, 2009}}</ref>]]
 
The [[three-dimensional]] wind field in a tropical cyclone can be separated into two components: a "primary circulation" and a "[[secondary circulation]]". The primary circulation is the rotational part of the flow; it is purely circular. The secondary circulation is the overturning (in-up-out-down) part of the flow; it is in the [[radiate|radial]] and vertical directions. The primary circulation has the strongest winds and is responsible for the majority of the damage a storm causes, while the secondary circulation is slower but governs the [[energetics]] of the storm.
 
=== Sekundarna circulacija: Karnotova toplotna mašina ===
A tropical cyclone's primary energy source is the evaporation of [[water]] from the [[ocean]] surface, which ultimately [[condensation|recondenses]] into clouds and rain when the warm moist air rises and cools to [[Saturated fluid|saturation]]. The energetics of the system may be idealized as an atmospheric [[Carnot heat engine]].<ref name="JAS Emanuel 1986">{{cite doi | 10.1175/1520-0469(1986)043<0585:AASITF>2.0.CO;2}}</ref> First, inflowing air near the surface acquires heat primarily via evaporation of water (i.e. [[latent heat]]) at the temperature of the warm ocean surface (during evaporation, the ocean cools and the air warms). Second, the warmed air rises and cools within the eyewall while conserving total heat content (latent heat is simply converted to [[sensible heat]] during [[condensation]]). Third, air outflows and loses heat via [[Thermal radiation|infrared radiation]] to space at the temperature of the cold [[tropopause]]. Finally, air [[Subsidence (atmosphere)|subsides]] and warms at the outer edge of the storm while conserving total heat content. The first and third legs are nearly [[isothermal]], while the second and fourth legs are nearly [[isentropic]]. This in-up-out-down overturning flow is known as the [[Secondary flow|secondary circulation]]. The Carnot perspective provides an [[Tropical cyclone#Maximum potential intensity|upper bound]] on the maximum wind speed that a storm can attain.
 
Scientists estimate that a tropical cyclone releases heat energy at the rate of 50 to 200&nbsp;[[exajoule]]s (10<sup>18</sup>&nbsp;J) per day,<ref name="NOAA Question of the Month">{{cite web|url=http://www.aoml.noaa.gov/hrd/tcfaq/D7.html|title=NOAA FAQ: How much energy does a hurricane release?|date=August 2001|accessdate=June 30, 2009|publisher= National Oceanic & Atmospheric Administration }}</ref> equivalent to about 1&nbsp;PW (10<sup>15</sup>&nbsp;watt). This rate of energy release is equivalent to 70 times the [[world energy resources and consumption|world energy consumption]] of humans and 200 times the worldwide electrical generating capacity, or to exploding a 10-[[TNT equivalent|megaton]] [[nuclear bomb]] every 20&nbsp;minutes.<ref name="NOAA Question of the Month"/><ref name="UCAR">{{cite web|url=http://www.ucar.edu/news/features/hurricanes/index.jsp|title=Hurricanes: Keeping an eye on weather's biggest bullies.|date=March 31, 2006|publisher= University Corporation for Atmospheric Research |accessdate=May 7, 2009}}</ref>
 
=== Primarna cirkulacija: rotirajuči vetrovi ===
The primary rotating flow in a tropical cyclone results from the [[conservation of angular momentum]] by the secondary circulation. [[Absolute angular momentum]] on a rotating planet <math>M</math> is given by
 
:<math>M = \frac{1}{2}fr^2 + vr</math>
 
where <math>f</math> is the [[Coriolis parameter]], <math>v</math> is the azimuthal (i.e. rotating) wind speed, and <math>r</math> is the radius to the axis of rotation. The first term on the right hand side is the component of planetary angular momentum that projects onto the local vertical (i.e. the axis of rotation). The second term on the right hand side is the relative angular momentum of the circulation itself with respect to the axis of rotation. Because the planetary angular momentum term vanishes at the equator (where <math>f=0</math> ), tropical cyclones rarely [[Tropical cyclone#Formation|form]] within 5° of the equator.<ref name="BAMS Zhang 1988" /><ref>{{cite web|url=http://www.soest.hawaii.edu/GG/ASK/hurricanes.html|title=Hurricanes and the equator|author=Barnes, Gary|publisher= University of Hawaii |accessdate=August 30, 2013}}</ref>
 
As air flows radially inward at low levels, it begins to rotate cyclonically in order to conserve angular momentum. Similarly, as rapidly rotating air flows radially outward near the tropopause, its cyclonic rotation decreases and ultimately changes sign at large enough radius, resulting in an upper-level [[anti-cyclone]]. The result is a vertical structure characterized by a strong [[cyclone]] at low levels and a strong [[anti-cyclone]] near the [[tropopause]]; from [[Thermal wind|thermal wind balance]], this corresponds to a system that is warmer at its center than in the surrounding environment at all altitudes (i.e. "warm-core"). From [[hydrostatic balance]], the warm core translates to lower pressure at the center at all altitudes, with the maximum pressure drop located at the surface.<ref name="MWR Frank 1977" />
 
=== Maksimum potencijalnog intenziteta ===
Due to surface friction, the inflow only partially conserves angular momentum. Thus, the sea surface lower boundary acts as both a source (evaporation) and sink (friction) of energy for the system. This fact leads to the existence of a theoretical upper bound on the strongest wind speed that a tropical cyclone can attain. Because evaporation increases linearly with wind speed (just as climbing out of a pool feels much colder on a windy day), there is a positive feedback on energy input into the system known as the Wind-Induced Surface Heat Exchange (WISHE) feedback.<ref name="JAS Emanuel 1986" /> This feedback is offset when frictional dissipation, which increases with the cube of the wind speed, becomes sufficiently large.
This upper bound is called the "maximum potential intensity", <math>v_p</math>, and is given by
 
:<math>v_p^2 = \frac{C_k}{C_d}\frac{T_s - T_o}{T_o}\Delta k</math>
 
where <math>T_s</math> is the temperature of the sea surface, <math>T_o</math> is the temperature of the outflow ([K]), <math>\Delta k</math> is the enthalpy difference between the surface and the overlying air ([J/kg]), and <math>C_k</math> and <math>C_d</math> are the surface [[Heat transfer coefficient|exchange coefficients]] ([[dimensionless]]) of enthalpy and momentum, respectively.<ref name="Bister_Emanuel_1998_MAP">{{cite doi | 10.1007/BF01030791 }}</ref> The surface-air enthalpy difference is taken as <math>\Delta k = k^*_s-k</math>, where <math>k^*_s</math> is the saturation [[enthalpy]] of air at sea surface temperature and sea-level pressure and <math>k</math> is the enthalpy of boundary layer air overlying the surface.
 
The maximum potential intensity is predominantly a function of the background environment alone (i.e. without a tropical cyclone), and thus this quantity can be used to determine which regions on Earth can support tropical cyclones of a given intensity, and how these regions may evolve in time.<ref name="Emanuel_2000_MWR">{{cite doi | 10.1175/1520-0493(2000)128<1139:ASAOTC>2.0.CO;2}}</ref><ref name="Knutson_etal_2010_NG">{{cite doi |10.1038/ngeo779}}</ref> Specifically, the maximum potential intensity has three components, but its [[Tropical cyclone#Characteristic values and variability on Earth|variability in space and time]] is due predominantly to the variability in the surface-air enthalpy difference component <math>\Delta k</math>.
 
==== Derivacija ====
A tropical cyclone may be viewed as a [[heat engine]] that converts input [[heat]] energy from the surface into [[mechanical energy]] that can be used to do [[mechanical work]] against surface friction. At equilibrium, the rate of net energy production in the system must equal the rate of energy loss due to frictional dissipation at the surface, i.e.
 
:<math>W_{in} = W_{out}</math>
 
The rate of energy loss per unit surface area from surface friction, <math>W_{out}</math>, is given by
 
:<math>W_{out} = C_d \rho |\mathbf{u}|^3</math>
 
where <math>\rho</math> is the density of near-surface air ([kg/m<sup>3</sup>]) and <math>|\mathbf{u}|</math> is the near surface wind speed ([m/s]).
 
The rate of energy production per unit surface area, <math>W_{in}</math> is given by
 
:<math>W_{in} = \epsilon Q_{in}</math>
 
where <math>\epsilon</math> is the heat engine efficiency and <math>Q_{in}</math> is the total rate of heat input into the system per unit surface area. Given that a tropical cyclone may be idealized as a [[Tropical cyclone#Secondary circulation: a Carnot heat engine|Carnot heat engine]], the Carnot heat engine efficiency is given by
 
:<math>\epsilon = \frac{T_s-T_o}{T_s}</math>
 
Heat (enthalpy) per unit mass is given by
 
:<math>k = C_pT + L_vq</math>
 
where <math>C_p</math> is the heat capacity of air, <math>T</math> is air temperature, <math>L_v</math> is the latent heat of vaporization, and <math>q</math> is the concentration of water vapor. The first component corresponds to [[sensible heat]] and the second to [[latent heat]].
 
There are two sources of heat input. The dominant source is the input of heat at the surface, primarily due to evaporation. The bulk aerodynamic formula for the rate of heat input per unit area at the surface, <math>Q_{in:k}</math>, is given by
 
:<math>Q_{in:k} = C_k \rho |\mathbf{u}|\Delta k</math>
 
where <math>\Delta k = k^*_s-k</math> represents the enthalpy difference between the ocean surface and the overlying air. The second source is the internal sensible heat generated from frictional dissipation (equal to <math>W_{out}</math>), which occurs near the surface within the tropical cyclone and is recycled to the system.
 
:<math>Q_{in:friction} = C_d \rho |\mathbf{u}|^3</math>
 
Thus, the total rate of net energy production per unit surface area is given by
 
:<math>W_{in} = \frac{T_s-T_o}{T_s}\left(C_k \rho |\mathbf{u}|\Delta k + C_d \rho |\mathbf{u}|^3\right)</math>
 
Setting <math>W_{in} = W_{out}</math> and taking <math>|\mathbf{u}| \approx v</math> (i.e. the rotational wind speed is dominant) leads to the solution for <math>v_p</math> given above. This derivation assumes that total energy input and loss within the system can be approximated by their values at the radius of maximum wind. The inclusion of <math>Q_{in:friction}</math> acts to multiply the total heat input rate by the factor <math>\frac{T_s}{T_o}</math>. Mathematically, this has the effect of replacing <math>T_s</math> with <math>T_o</math> in the denominator of the Carnot efficiency.
 
An alternative definition for the maximum potential intensity, which is mathematically equivalent to the above formulation, is
 
:<math>v_p = \sqrt{\frac{T_s}{T_o}\frac{C_k}{C_d}(CAPE^*_s-CAPE_b)|_m}</math>
 
where CAPE stands for the [[Convective Available Potential Energy]], <math>CAPE^*_s</math> is the CAPE of an air parcel lifted from saturation at sea level in reference to the environmental [[Atmospheric sounding|sounding]], <math>CAPE_b</math> is the CAPE of the boundary layer air, and both quantities are calculated at the radius of maximum wind.<ref name="Bister_Emanuel_2002_JGRA">{{cite doi|10.1029/2001JD000776}}</ref>
 
==== Karakteristične vrednosti i varijabilnost na Zemlji ====
On Earth, a characteristic temperature for <math>T_s</math> is 300 K and for <math>T_o</math> is 200 K, corresponding to a Carnot efficiency of <math>\epsilon = 1/3</math>. The ratio of the surface exchange coefficients, <math>C_k/C_d</math>, is typically taken to be 1. However, observations suggest that the drag coefficient <math>C_d</math> varies with wind speed and may decrease at high wind speeds within the boundary layer of a mature hurricane.<ref name="Powell_etal_2003_Nat">{{cite doi|10.1038/nature01481 }}</ref> Additionally, <math>C_k</math> may vary at high wind speeds due to the effect of [[sea spray]] on evaporation within the boundary layer.<ref name="Bell_etal_2012">{{cite doi | 10.1175/JAS-D-11-0276.1 }}</ref>
 
A characteristic value of the maximum potential intensity, <math>v_p</math>, is 80&nbsp;m/s. However, this quantity varies significantly across space and time, particularly within the [[season|seasonal cycle]], spanning a range of 0–100&nbsp;m/s.<ref name="Bister_Emanuel_2002_JGRA" /> This variability is primarily due to variabliity in the surface enthalpy disequilibrium ( <math>\Delta k</math> ) as well as in the thermodynamic structure of the troposphere, which are controlled by the large-scale dynamics of the tropical climate. These processes are modulated by factors including the sea surface temperature (and underlying ocean dynamics), background near-surface wind speed, and the vertical structure of atmospheric radiative heating.<ref name="Emanuel_Sobel_2013_JAMES">{{cite doi|10.1002/jame.20032}}</ref> The nature of this modulation is complex, particularly on climate time-scales (decades or longer). On shorter time-scales, variability in the maximum potential intensity is commonly linked to sea surface temperature perturbations from the tropical mean, as regions with relatively warm water have thermodynamic states much more capable of sustaining a tropical cyclone than regions with relatively cold water.<ref name="Sobel_Bretherton_2000_JC">{{cite doi | 10.1175/1520-0442(2000)013<4378:MTPIAS>2.0.CO;2}}</ref> However, this relationship is indirect via the large-scale dynamics of the tropics; the direct influence of the absolute sea surface temperature on <math>v_p</math> is weak in comparison.
 
=== Interakcija sa okeanom ===
[[File:GulfMexTemps 2005Hurricanes.gif|thumb|Chart displaying the drop in surface temperature in the [[Gulf of Mexico]] as Hurricanes [[Hurricane Katrina|Katrina]] and [[Hurricane Rita|Rita]] passed over]]
 
The passage of a tropical cyclone over the ocean causes the upper layers of the ocean to cool substantially, which can influence subsequent cyclone development. This cooling is primarily caused by wind-driven mixing of cold water from deeper in the ocean with the warm surface waters. This effect results in a negative feedback process that can inhibit further development or lead to weakening. Additional cooling may come in the form of cold water from falling raindrops (this is because the atmosphere is cooler at higher altitudes). Cloud cover may also play a role in cooling the ocean, by shielding the ocean surface from direct sunlight before and slightly after the storm passage. All these effects can combine to produce a dramatic drop in sea surface temperature over a large area in just a few days.<ref name="NASA Cooling">{{cite web|author=D'Asaro, Eric A. and Black, Peter G. |url=http://web.archive.org/web/20120330131407/http://iop.apl.washington.edu/opd/user/dasaro/DENNIS/HurrConf.pdf|format=PDF|title=J8.4 Turbulence in the Ocean Boundary Layer Below Hurricane Dennis|year=2006|accessdate=February 22, 2008|publisher= University of Washington }}</ref>
 
== Safir-Simpsonova skala uragana ==
Linija 16 ⟶ 153:
* Kategorija 5 - vetar snažniji od 249 km/h. Oštećuje: nosi krovove, zgrade se ruše, masovna evakuacija 15 km uz obalu
 
[[Datoteka:7 zones dels ciclons tropicals.jpg|640px|center|Sedam zona tropskih ciklona]]
 
==References==
{{Reflist|2}}
 
== Literatura ==
{{Refbegin|2}}
*[http://web.archive.org/web/20101110075520/http://a-z-dictionaries.com/Hurricane_glossary.html Hurricane Glossary of Terms]
*[http://www.pakweather.com/2015/03/deadliest-world-tropical-cyclones.html List of World's Deadliest Tropical Cyclones]
*CDC - NIOSH [http://www.cdc.gov/niosh/topics/emres/flood.html Storm/Flood and Hurricane/Typhoon Response]
*[http://www.ncdc.noaa.gov/billions U.S. Billion-dollar Weather and Climate Events]
 
* Florent Beucher, Manuel de météorologie tropicale : des alizés au cyclone (2 tomes), Météo-France, coll. « Cours et Manuel, 897 pp. »,‎ 25 mai 2010 (ISBN 978-2-11-099391-5, présentation en ligne, lire en ligne [PDF]), p. 476 et 420
* Les cyclones sèment la tempête chez les scientifiques, article du Courrier International (pages 48–49, édition du 12 au 18 janvier 2006) : débat sur le réchauffement climatique et ses conséquences sur une possible augmentation du nombre de cyclones.
* Le résultat de recherches publié dans le magazine scientifique Nature du 4 août 2005, par Kerry Emanuel (« Aggravation de l'effet destructeur des cyclones tropicaux sur les 30 dernières années »).
* Henry Piddington, The Horn-book for the Law of Storms for the Indian and China Seas,‎ 1844
* Henry Piddington, The Sailor's Horn-book for the Law of Storms, London, Smith, Elder and Co.,‎ 1848, 360 p.
{{refend}}
 
== Vanjske veze ==
{{Commonscat|Tropical cyclones}}
*[http://www.nhc.noaa.gov/ US National Hurricane Center]&nbsp;– North Atlantic, Eastern Pacific
*[http://www.prh.noaa.gov/hnl/cphc/ Central Pacific Hurricane Center]&nbsp;– Central Pacific
*[http://www.jma.go.jp/en/typh/ Japan Meteorological Agency]&nbsp;– NW Pacific
*[http://www.rsmcnewdelhi.imd.gov.in/index.php?lang=en India Meteorological Department]&nbsp;– Bay of Bengal and the Arabian Sea
*[http://www.meteo.fr/temps/domtom/La_Reunion/webcmrs9.0/anglais/ Météo-France&nbsp;– La Reunion]&nbsp;– South Indian Ocean from 30°E to 90°E
*[http://www.met.gov.fj/ Fiji Meteorological Service]&nbsp;– South Pacific west of 160°E, north of 25° S
*[http://papers.ssrn.com/sol3/papers.cfm?abstract_id=2586947 Trends in tropical cyclone activity: Indian Ocean 1998-2014]
*[http://meteo.bmkg.go.id/siklon Indonesian Meteorological Department]&nbsp;– South Indian Ocean from 90°E to 125°E, north of 10°S
*[http://www.bom.gov.au/weather/cyclone/index.shtml Australian Bureau of Meteorology (TCWC's Perth, Darwin & Brisbane)].&nbsp;– South Indian Ocean & South Pacific Ocean from 90°E to 160°E, south of 10°S
*[http://metservice.com/ Meteorological Service of New Zealand Limited]&nbsp;– South Pacific west of 160°E, south of 25°S
 
 
[[Kategorija:Tropski cikloni| ]]