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{{Short description|Intensity indicator of tropical cyclone}}
The '''maximum sustained wind''' associated with a [[tropical cyclone]] is a common
indicator of the intensity of the storm. Within a mature tropical cyclone, it is found within the [[eyewall]] at a certain distance from the center, known as the [[radius of maximum wind]], or RMW. Unlike [[wind gust|gust]]s, the value of these winds are determined via their sampling and averaging the sampled results over a period of time. Wind measuring has been standardized globally to reflect the winds at {{convert|10|m|ft}} above [[Height above mean sea level#Uses|mean sea level]],{{#tag:ref|The Saffir–Simpson scale uses an elevation of {{convert|10|m|ft|abbr=on}} above mean sea level.<ref name="10mWind">{{cite journal|last1=Simiu|first1=Emil|last2=Vickery|first2=Peter|last3=Kareem|first3=Ahsan|date=July 2007|url=https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=860600|title=Relation Between Saffir-Simpson Hurricane Scale Wind Speeds and Peak 3-s Gust Speeds Over Open Terrain|series=Technical Notes|journal=[[Journal of Structural Engineering]]|volume=133|number=7|page=1043|location=[[Reston, Virginia]]|doi=10.1061/(ASCE)0733-9445(2007)133:7(1043)|doi-access=free|url-access=subscription}}</ref>|group="nb"|name="Sea level"}} and the maximum sustained wind represents the highest average wind over either a one-minute (US) or ten-minute time span (see [[#Definition|the definition, below]]), anywhere within the tropical cyclone. Surface winds are highly variable due to friction between the atmosphere and the Earth's surface, as well as near hills and mountains over land.

Over the ocean, [[Weather satellite|satellite]] [[Satellite imagery|imagery]] is often used to estimate the maximum sustained winds within a tropical cyclone. Land, ship, [[Hurricane Hunters|aircraft reconnaissance]] observations, and [[weather radar|radar]] imagery can also estimate this quantity, when available. This value helps determine the damage potential of a tropical cyclone, through use of such scales as the [[Saffir–Simpson scale]].

==Definition==
{{See also|Radius of maximum wind|}}
The maximum sustained wind normally occurs at a distance from the center known as the radius of maximum wind, within a mature tropical cyclone's eyewall, before winds decrease at farther distances away from a tropical cyclone's center.<ref>Brian W. Blanchard and S. A. Hsu. [http://www.nwas.org/ej/pdf/2006-EJ4.pdf ON THE RADIAL VARIATION OF THE TANGENTIAL WIND SPEED OUTSIDE THE RADIUS OF MAXIMUM WIND DURING HURRICANE WILMA (2005).] {{webarchive|url=https://web.archive.org/web/20120905133143/http://www.nwas.org/ej/pdf/2006-EJ4.pdf |date=2012-09-05 }} Retrieved on 2008-07-04.</ref> Most weather agencies use the definition for sustained winds recommended by the [[World Meteorological Organization]] (WMO), which specifies measuring winds at a height of {{convert|10|m|ft}} for 10 minutes, and then taking the average. However, the United States [[National Weather Service]] defines sustained winds within tropical cyclones by averaging winds over a period of one minute, measured at the same {{convert|10|m|ft}} height.<ref name="NWSM Defs">{{cite web | author = Tropical Cyclone Weather Services Program | title = Tropical cyclone definitions | url = http://www.weather.gov/directives/sym/pd01006004curr.pdf | date = June 1, 2006 | access-date = 2006-11-30 | publisher = [[National Weather Service]]}}</ref> This is an important distinction, as the value of the highest one-minute sustained wind is about 14% greater than a ten-minute sustained wind over the same period.<ref>[[United States Navy]]: {{Cite web |url=http://www.nrlmry.navy.mil/~chu/chap6/se200.htm |title=SECTION 2. INTENSITY OBSERVATION AND FORECAST ERRORS |access-date=2008-07-04 |archive-url=https://web.archive.org/web/20070916205204/http://www.nrlmry.navy.mil/~chu/chap6/se200.htm |archive-date=2007-09-16 |url-status=bot: unknown }} Retrieved on 2018-10-07.</ref>

==Estimation and measurement==
{{Main|Tropical cyclone observation}}

In most tropical cyclone basins, use of the satellite-based [[Dvorak technique]] is the primary method used to estimate a tropical cyclone's maximum sustained winds.<ref name="ODT">{{cite web|title=Objective Dvorak Technique|url=http://cimss.ssec.wisc.edu/tropic/research/products/dvorak/odt.html|publisher=[[University of Wisconsin–Madison]]|access-date=2006-05-29}}</ref> The extent of spiral banding and difference in temperature between the [[Eye (cyclone)|eye]] and eyewall is used within the technique to assign a maximum sustained wind and pressure.<ref>[[Chris Landsea]] (June 8, 2010). [http://www.aoml.noaa.gov/hrd/tcfaq/H1.html Subject: H1) What is the Dvorak technique and how is it used?] [[Atlantic Oceanographic and Meteorological Laboratory]]. Retrieved on 2011-01-14.</ref> [[Atmospheric pressure|Central pressure]] values for their centers of [[low pressure]] are approximate. The tracking of individual clouds on minutely satellite imagery could be used in the future in estimating surface winds speeds for tropical cyclones.<ref>A. F. Hasler, K. Palaniappan, C. Kambhammetu, P. Black, E. Uhlhorn, and D. Chesters. [http://ams.allenpress.com/archive/1520-0477/79/11/pdf/i1520-0477-79-11-2483.pdf High-Resolution Wind Fields within the Inner Core and Eye of a Mature Tropical Cyclone from GOES 1-min Images.] Retrieved on 2008-07-04.</ref>

Ship and land observations are also used, when available. In the Atlantic as well as the Central and Eastern Pacific basins, reconnaissance aircraft are still utilized to fly through tropical cyclones to determine flight level winds, which can then be adjusted to provide a fairly reliable estimate of maximum sustained winds. A reduction of 10 percent of the winds sampled at flight level is used to estimate the maximum sustained winds near the surface, which has been determined during the past decade through the use of [[GPS]] [[Dropsonde|dropwindsondes]].<ref name="Franklin">Franklin, James L., Michael L. Black, and Krystal Valde. [http://cat.inist.fr/?aModele=afficheN&cpsidt=15034652 GPS dropwindsonde wind profiles in hurricanes and their operational implications.] Retrieved on 2008-07-04.</ref> [[Doppler weather radar]] can be used in the same manner to determine surface winds with tropical cyclones near land.<ref>J. TUTTLE and R. GALL. [http://cat.inist.fr/?aModele=afficheN&cpsidt=1801644 A single-radar technique for estimating the winds in tropical cyclones.] Retrieved on 2008-06-12.</ref>
{| class="wikitable" style="clear:all;"
|+ '''Satellite Images of Selected Tropical Cyclones and Associated [[Dvorak technique#Details of the method|T-Number]] from Dvorak technique'''
|-
| [[File:Wilma-17-1315z-T30-discussion1500z.png]]
| [[File:Dennis-06-1445z-T40-discussion1500z.png]]
| [[File:Jeanne-22-1945z-T50-discussion2100z.png]]
| [[File:Emily-14-1915z-T60-discussion15-0300z.png]]
|- align=center
| [[Hurricane Wilma|Tropical Storm Wilma]] at T3.0
| [[Hurricane Dennis|Tropical Storm Dennis]] at T4.0
| [[Hurricane Jeanne]] at T5.0
| [[Hurricane Emily (2005)|Hurricane Emily]] at T6.0
|}

==Variation==
{{See also|Planetary boundary layer}}
Friction between the atmosphere and the Earth's surface causes a 20% reduction in the wind at the surface of the Earth.<ref>{{cite web|first =Jeff|last = Haby|url =http://www.theweatherprediction.com/habyhints/10/ |title = The Importance of Friction|website = theweatherprediction.com}}</ref> Surface roughness also leads to significant variation of wind speeds. Over land, winds maximize at hill or [[mountain crest]]s, while sheltering leads to lower wind speeds in valleys and lee slopes.<ref>[http://www.nhc.noaa.gov/jht/05-07reports/JHT07_Miller_midyear.pdf Mapping of Topographic Effects on Maximum Sustained Surface Wind Speeds in Landfalling Hurricanes.] Retrieved on 2008-07-04.</ref> Compared to over water, maximum sustained winds over land average 8% lower.<ref>Peter Black. [http://www.aoml.noaa.gov/hrd/hurdat/august01/Franklin_response(2).txt Subject: Re: Offshore vs nearshore sonde composite.] Retrieved on 2008-07-04.</ref> More especially, over a city or rough terrain, the wind gradient effect could cause a reduction of 40% to 50% of the [[geostrophic wind]] speed aloft; while over open water or ice, the reduction is between 10% and 30%.<ref name="Franklin"/><ref>{{cite book | last = Harrison | first = Roy | title = Understanding Our Environment | url = https://archive.org/details/understandingour00harr_959 | url-access = limited | publisher = Royal Society of Chemistry | location = Cambridge | year = 1999 | isbn = 0-85404-584-8 | pages = [https://archive.org/details/understandingour00harr_959/page/n27 11]}}</ref><ref name=Russell>{{cite book | last = Thompson | first = Russell | title = Atmospheric Processes and Systems | url = https://archive.org/details/atmosphericproce00thom | url-access = limited | publisher = Routledge | location = New York | year = 1998 | isbn = 0-415-17145-8 | pages = [https://archive.org/details/atmosphericproce00thom/page/n124 102]–103 }}</ref>

==Relationship to tropical cyclone strength scales==
{{Main|Tropical cyclone scales}}
In most basins, maximum sustained winds are used to define the category of a tropical cyclone on each basin's [[tropical cyclone scale]]. In the Atlantic and northeast Pacific oceans, the [[Saffir–Simpson scale]] is used. This scale can be used to determine possible storm surge and damage impact on land. In most basins, the category of the tropical cyclone (for example, tropical depression, tropical storm, hurricane/typhoon, super typhoon, depression, deep depression, intense tropical cyclone) is determined from the cyclone's maximum sustained wind over one minute.

==Notes==
{{Reflist|group=nb}}

==References==
{{Reflist|2}}

{{good article}}

{{DEFAULTSORT:Maximum Sustained Wind}}
[[Category:Wind]]
[[Category:Tropical cyclone meteorology|Tropical cyclone meteorology]]

Maximum sustained wind - Revision history

imported>OAbot: Open access bot: url-access updated in citation with #oabot.