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trough</span> </div> </a> <button aria-controls="toc-Types_of_trough-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Types of trough subsection</span> </button> <ul id="toc-Types_of_trough-sublist" class="vector-toc-list"> <li id="toc-Inverted_trough" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Inverted_trough"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.1</span> <span>Inverted trough</span> </div> </a> <ul id="toc-Inverted_trough-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Lee_trough" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Lee_trough"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.2</span> <span>Lee trough</span> </div> </a> <ul id="toc-Lee_trough-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Weather_associated" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Weather_associated"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>Weather associated</span> </div> </a> <ul id="toc-Weather_associated-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-See_also" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#See_also"> <div class="vector-toc-text"> <span class="vector-toc-numb">5</span> <span>See also</span> </div> </a> <ul id="toc-See_also-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-References" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#References"> <div class="vector-toc-text"> <span class="vector-toc-numb">6</span> <span>References</span> </div> </a> <ul id="toc-References-sublist" class="vector-toc-list"> </ul> </li> </ul> </div> </div> </nav> </div> </div> <div class="mw-content-container"> <main id="content" class="mw-body"> <header class="mw-body-header vector-page-titlebar"> <nav aria-label="Contents" class="vector-toc-landmark"> <div id="vector-page-titlebar-toc" class="vector-dropdown vector-page-titlebar-toc vector-button-flush-left" > <input type="checkbox" id="vector-page-titlebar-toc-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-page-titlebar-toc" class="vector-dropdown-checkbox " aria-label="Toggle the table of contents" > <label id="vector-page-titlebar-toc-label" for="vector-page-titlebar-toc-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-listBullet mw-ui-icon-wikimedia-listBullet"></span> <span class="vector-dropdown-label-text">Toggle the table of contents</span> </label> <div class="vector-dropdown-content"> <div id="vector-page-titlebar-toc-unpinned-container" class="vector-unpinned-container"> </div> </div> </div> </nav> <h1 id="firstHeading" class="firstHeading mw-first-heading"><span class="mw-page-title-main">Trough (meteorology)</span></h1> <div id="p-lang-btn" class="vector-dropdown mw-portlet mw-portlet-lang" > <input type="checkbox" id="p-lang-btn-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-p-lang-btn" class="vector-dropdown-checkbox mw-interlanguage-selector" aria-label="Go to an article in another language. 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class="interlanguage-link interwiki-ast mw-list-item"><a href="https://ast.wikipedia.org/wiki/Fanguada" title="Fanguada – Asturian" lang="ast" hreflang="ast" data-title="Fanguada" data-language-autonym="Asturianu" data-language-local-name="Asturian" class="interlanguage-link-target"><span>Asturianu</span></a></li><li class="interlanguage-link interwiki-ca mw-list-item"><a href="https://ca.wikipedia.org/wiki/T%C3%A0lveg_(meteorologia)" title="Tàlveg (meteorologia) – Catalan" lang="ca" hreflang="ca" data-title="Tàlveg (meteorologia)" data-language-autonym="Català" data-language-local-name="Catalan" class="interlanguage-link-target"><span>Català</span></a></li><li class="interlanguage-link interwiki-cs mw-list-item"><a href="https://cs.wikipedia.org/wiki/Br%C3%A1zda_n%C3%ADzk%C3%A9ho_tlaku_vzduchu" title="Brázda nízkého tlaku vzduchu – Czech" lang="cs" hreflang="cs" data-title="Brázda nízkého tlaku vzduchu" data-language-autonym="Čeština" data-language-local-name="Czech" class="interlanguage-link-target"><span>Čeština</span></a></li><li class="interlanguage-link interwiki-de mw-list-item"><a href="https://de.wikipedia.org/wiki/Trog_(Meteorologie)" title="Trog (Meteorologie) – German" lang="de" hreflang="de" data-title="Trog (Meteorologie)" data-language-autonym="Deutsch" data-language-local-name="German" class="interlanguage-link-target"><span>Deutsch</span></a></li><li class="interlanguage-link interwiki-es mw-list-item"><a href="https://es.wikipedia.org/wiki/Vaguada_(meteorolog%C3%ADa)" title="Vaguada (meteorología) – Spanish" lang="es" hreflang="es" data-title="Vaguada (meteorología)" data-language-autonym="Español" data-language-local-name="Spanish" class="interlanguage-link-target"><span>Español</span></a></li><li class="interlanguage-link interwiki-eu mw-list-item"><a href="https://eu.wikipedia.org/wiki/Aska_(meteorologia)" title="Aska (meteorologia) – Basque" lang="eu" hreflang="eu" data-title="Aska (meteorologia)" data-language-autonym="Euskara" data-language-local-name="Basque" class="interlanguage-link-target"><span>Euskara</span></a></li><li class="interlanguage-link interwiki-fa mw-list-item"><a href="https://fa.wikipedia.org/wiki/%D9%86%D8%A7%D9%88%D9%87_(%D9%87%D9%88%D8%A7%D8%B4%D9%86%D8%A7%D8%B3%DB%8C)" title="ناوه (هواشناسی) – Persian" lang="fa" hreflang="fa" data-title="ناوه (هواشناسی)" data-language-autonym="فارسی" data-language-local-name="Persian" class="interlanguage-link-target"><span>فارسی</span></a></li><li class="interlanguage-link interwiki-fr mw-list-item"><a href="https://fr.wikipedia.org/wiki/Creux_barom%C3%A9trique" title="Creux barométrique – French" lang="fr" hreflang="fr" data-title="Creux barométrique" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-ko mw-list-item"><a href="https://ko.wikipedia.org/wiki/%EA%B8%B0%EC%95%95%EA%B3%A8" title="기압골 – Korean" lang="ko" hreflang="ko" data-title="기압골" data-language-autonym="한국어" data-language-local-name="Korean" class="interlanguage-link-target"><span>한국어</span></a></li><li class="interlanguage-link interwiki-id mw-list-item"><a href="https://id.wikipedia.org/wiki/Palung_(meteorologi)" title="Palung (meteorologi) – Indonesian" lang="id" hreflang="id" data-title="Palung (meteorologi)" data-language-autonym="Bahasa Indonesia" data-language-local-name="Indonesian" class="interlanguage-link-target"><span>Bahasa Indonesia</span></a></li><li class="interlanguage-link interwiki-it mw-list-item"><a href="https://it.wikipedia.org/wiki/Saccatura" title="Saccatura – Italian" lang="it" hreflang="it" data-title="Saccatura" data-language-autonym="Italiano" data-language-local-name="Italian" class="interlanguage-link-target"><span>Italiano</span></a></li><li class="interlanguage-link interwiki-lmo mw-list-item"><a href="https://lmo.wikipedia.org/wiki/Insaccadura" title="Insaccadura – Lombard" lang="lmo" hreflang="lmo" data-title="Insaccadura" data-language-autonym="Lombard" data-language-local-name="Lombard" class="interlanguage-link-target"><span>Lombard</span></a></li><li class="interlanguage-link interwiki-nl mw-list-item"><a href="https://nl.wikipedia.org/wiki/Trog_(meteorologie)" title="Trog (meteorologie) – Dutch" lang="nl" hreflang="nl" data-title="Trog (meteorologie)" data-language-autonym="Nederlands" data-language-local-name="Dutch" class="interlanguage-link-target"><span>Nederlands</span></a></li><li class="interlanguage-link interwiki-ja mw-list-item"><a href="https://ja.wikipedia.org/wiki/%E6%B0%97%E5%9C%A7%E3%81%AE%E8%B0%B7" title="気圧の谷 – Japanese" lang="ja" hreflang="ja" data-title="気圧の谷" data-language-autonym="日本語" data-language-local-name="Japanese" class="interlanguage-link-target"><span>日本語</span></a></li><li class="interlanguage-link interwiki-no mw-list-item"><a href="https://no.wikipedia.org/wiki/Tr%C3%A5g" title="Tråg – Norwegian Bokmål" lang="nb" hreflang="nb" data-title="Tråg" data-language-autonym="Norsk bokmål" data-language-local-name="Norwegian Bokmål" class="interlanguage-link-target"><span>Norsk bokmål</span></a></li><li class="interlanguage-link interwiki-nn mw-list-item"><a href="https://nn.wikipedia.org/wiki/Tr%C3%A5g" title="Tråg – Norwegian Nynorsk" lang="nn" hreflang="nn" data-title="Tråg" data-language-autonym="Norsk nynorsk" data-language-local-name="Norwegian Nynorsk" class="interlanguage-link-target"><span>Norsk nynorsk</span></a></li><li class="interlanguage-link interwiki-pl mw-list-item"><a href="https://pl.wikipedia.org/wiki/Zatoka_niskiego_ci%C5%9Bnienia" title="Zatoka niskiego ciśnienia – Polish" lang="pl" hreflang="pl" data-title="Zatoka niskiego ciśnienia" data-language-autonym="Polski" data-language-local-name="Polish" class="interlanguage-link-target"><span>Polski</span></a></li><li class="interlanguage-link interwiki-pt mw-list-item"><a href="https://pt.wikipedia.org/wiki/Cavado" title="Cavado – Portuguese" lang="pt" hreflang="pt" data-title="Cavado" data-language-autonym="Português" data-language-local-name="Portuguese" class="interlanguage-link-target"><span>Português</span></a></li><li class="interlanguage-link interwiki-ru mw-list-item"><a href="https://ru.wikipedia.org/wiki/%D0%91%D0%B0%D1%80%D0%B8%D1%87%D0%B5%D1%81%D0%BA%D0%B0%D1%8F_%D0%BB%D0%BE%D0%B6%D0%B1%D0%B8%D0%BD%D0%B0" title="Барическая ложбина – Russian" lang="ru" hreflang="ru" data-title="Барическая ложбина" data-language-autonym="Русский" data-language-local-name="Russian" class="interlanguage-link-target"><span>Русский</span></a></li><li class="interlanguage-link interwiki-simple mw-list-item"><a href="https://simple.wikipedia.org/wiki/Trough_(meteorology)" title="Trough (meteorology) – Simple English" lang="en-simple" hreflang="en-simple" data-title="Trough (meteorology)" data-language-autonym="Simple English" data-language-local-name="Simple English" class="interlanguage-link-target"><span>Simple English</span></a></li><li class="interlanguage-link interwiki-fi mw-list-item"><a href="https://fi.wikipedia.org/wiki/Matalan_sola" title="Matalan sola – Finnish" lang="fi" hreflang="fi" data-title="Matalan sola" data-language-autonym="Suomi" data-language-local-name="Finnish" class="interlanguage-link-target"><span>Suomi</span></a></li><li class="interlanguage-link interwiki-sv mw-list-item"><a href="https://sv.wikipedia.org/wiki/Tr%C3%A5g_(meteorologi)" title="Tråg (meteorologi) – Swedish" lang="sv" hreflang="sv" data-title="Tråg (meteorologi)" data-language-autonym="Svenska" data-language-local-name="Swedish" class="interlanguage-link-target"><span>Svenska</span></a></li><li class="interlanguage-link interwiki-tr mw-list-item"><a href="https://tr.wikipedia.org/wiki/Yatak_(meteoroloji)" title="Yatak (meteoroloji) – Turkish" lang="tr" hreflang="tr" data-title="Yatak (meteoroloji)" data-language-autonym="Türkçe" data-language-local-name="Turkish" class="interlanguage-link-target"><span>Türkçe</span></a></li><li class="interlanguage-link interwiki-uk mw-list-item"><a href="https://uk.wikipedia.org/wiki/%D0%91%D0%B0%D1%80%D0%B8%D1%87%D0%BD%D0%B0_%D1%83%D0%BB%D0%BE%D0%B3%D0%BE%D0%B2%D0%B8%D0%BD%D0%B0" title="Барична улоговина – Ukrainian" lang="uk" hreflang="uk" data-title="Барична улоговина" data-language-autonym="Українська" data-language-local-name="Ukrainian" class="interlanguage-link-target"><span>Українська</span></a></li><li class="interlanguage-link interwiki-vi mw-list-item"><a href="https://vi.wikipedia.org/wiki/R%C3%A3nh_(th%E1%BB%9Di_ti%E1%BA%BFt)" title="Rãnh (thời tiết) – Vietnamese" lang="vi" hreflang="vi" data-title="Rãnh (thời tiết)" data-language-autonym="Tiếng Việt" data-language-local-name="Vietnamese" class="interlanguage-link-target"><span>Tiếng Việt</span></a></li><li class="interlanguage-link interwiki-wuu mw-list-item"><a href="https://wuu.wikipedia.org/wiki/%E4%BD%8E%E5%8E%8B%E6%A7%BD" title="低压槽 – Wu" lang="wuu" hreflang="wuu" data-title="低压槽" data-language-autonym="吴语" data-language-local-name="Wu" class="interlanguage-link-target"><span>吴语</span></a></li><li class="interlanguage-link interwiki-zh-yue mw-list-item"><a href="https://zh-yue.wikipedia.org/wiki/%E4%BD%8E%E5%A3%93%E6%A7%BD" title="低壓槽 – Cantonese" lang="yue" hreflang="yue" data-title="低壓槽" data-language-autonym="粵語" data-language-local-name="Cantonese" class="interlanguage-link-target"><span>粵語</span></a></li><li class="interlanguage-link interwiki-zh mw-list-item"><a href="https://zh.wikipedia.org/wiki/%E4%BD%8E%E5%A3%93%E6%A7%BD" title="低壓槽 – Chinese" lang="zh" hreflang="zh" data-title="低壓槽" data-language-autonym="中文" data-language-local-name="Chinese" class="interlanguage-link-target"><span>中文</span></a></li> </ul> <div class="after-portlet after-portlet-lang"><span class="wb-langlinks-edit wb-langlinks-link"><a href="https://www.wikidata.org/wiki/Special:EntityPage/Q2454987#sitelinks-wikipedia" title="Edit 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class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none">Elongated region of low atmospheric pressure</div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Trough.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/c/c6/Trough.jpg/220px-Trough.jpg" decoding="async" width="220" height="165" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/c/c6/Trough.jpg/330px-Trough.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/c/c6/Trough.jpg 2x" data-file-width="400" data-file-height="300" /></a><figcaption>Representation of alternating troughs and ridges in upper-level <a href="/wiki/Westerlies" title="Westerlies">westerlies</a> for the <a href="/wiki/Northern_Hemisphere" title="Northern Hemisphere">Northern Hemisphere</a>, with regions of convergence and divergence labeled.</figcaption></figure> <p>A <b>trough</b> is an elongated region of relatively low <a href="/wiki/Atmospheric_pressure" title="Atmospheric pressure">atmospheric pressure</a> without a closed <a href="/wiki/Isobar_(meteorology)" class="mw-redirect" title="Isobar (meteorology)">isobaric contour</a> that would define it as a <a href="/wiki/Low-pressure_area" title="Low-pressure area">low pressure area</a>. Since low pressure implies a low <a href="/wiki/Geopotential_height" title="Geopotential height">height</a> on a pressure surface, <a href="/wiki/Valley" title="Valley">troughs</a> and <a href="/wiki/Ridge_(meteorology)" title="Ridge (meteorology)">ridges</a> refer to features in an identical sense as those on a <a href="/wiki/Topographic_map" title="Topographic map">topographic map</a>. </p><p>Troughs may be at the surface, or aloft, at altitude. Near-surface troughs sometimes mark a <a href="/wiki/Weather_front" title="Weather front">weather front</a> associated with clouds, showers, and a wind direction shift. Upper-level troughs in the <a href="/wiki/Jet_stream" title="Jet stream">jet stream</a> (as shown in diagram) reflect <a href="/wiki/Cyclonic_rotation" title="Cyclonic rotation">cyclonic</a> filaments of <a href="/wiki/Vorticity" title="Vorticity">vorticity</a>. Their motion induces upper-level wind divergence, lifting and cooling the air ahead (downstream) of the trough and helping to produce cloudy and rain conditions there. </p><p>Unlike fronts, there is not a universal symbol for a trough on a <a href="/wiki/Surface_weather_analysis" title="Surface weather analysis">surface weather analysis</a> chart. The weather charts in some countries or regions mark troughs by a line. In the United States, a trough may be marked as a dashed line or bold line. In the UK, Hong Kong<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> and Fiji,<sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> it is represented by a bold line extended from a low pressure center<sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> or between two low pressure centers;<sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> in Macau<sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> and Australia,<sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> it is a dashed line. If they are not marked, troughs may still be identified as an extension of isobars away from a <a href="/wiki/Pressure_system" title="Pressure system">low pressure center</a>. </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Description">Description</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Trough_(meteorology)&action=edit&section=1" title="Edit section: Description"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Nov-12-2012-7am.gif" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/8/86/Nov-12-2012-7am.gif/220px-Nov-12-2012-7am.gif" decoding="async" width="220" height="179" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/8/86/Nov-12-2012-7am.gif/330px-Nov-12-2012-7am.gif 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/8/86/Nov-12-2012-7am.gif/440px-Nov-12-2012-7am.gif 2x" data-file-width="565" data-file-height="460" /></a><figcaption>A very large trough (about 8000 km or more) crosses the North Atlantic Ocean from north east to south west. The elongated cloud is surrounded by two big areas of higher atmospheric pressure, clearly shown with no clouds at all.</figcaption></figure> <p>A trough is an elongated area of lower air pressure. Since pressure is closely linked to wind, there are often changes in wind direction across a trough. </p><p>If a trough forms in the mid-latitudes, a temperature difference at some distance between the two sides of the trough usually exists and the trough might become a <a href="/wiki/Weather_front" title="Weather front">weather front</a> at some point. However, such a weather front is usually less convective than a trough in the tropics or subtropics (such as a <a href="/wiki/Tropical_wave" title="Tropical wave">tropical wave</a>). Inversely, sometimes collapsed frontal systems will degenerate into troughs. </p><p>Sometimes the region between two high pressure centers may also assume the character of a trough when there is a detectable wind shift noted at the surface. In the absence of a wind shift, the region is designated a <a href="/wiki/Col_(meteorology)" title="Col (meteorology)">col</a>, akin to a <a href="/wiki/Geographic_saddle" class="mw-redirect" title="Geographic saddle">geographic saddle</a> between two mountain peaks. </p> <div class="mw-heading mw-heading2"><h2 id="Formation">Formation</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Trough_(meteorology)&action=edit&section=2" title="Edit section: Formation"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>A trough is the result of the movements of the air in the atmosphere. In regions where there is upward movement near the ground and divergence at altitude, there is a loss of mass. The pressure becomes lower at this point. </p><p>At upper levels of the atmosphere, this occurs when there is a meeting of a mass of cold air and another hot one along a thin ribbon called a frontal <a href="/wiki/Baroclinicity" class="mw-redirect" title="Baroclinicity">baroclinic</a> zone. We then have the creation of a <a href="/wiki/Jet_stream" title="Jet stream">jet stream</a> that plunges the cold air towards the equator and hot air towards the poles, creating a ripple in the circulation that is called a <a href="/wiki/Rossby_wave" title="Rossby wave">Rossby wave</a>.<sup id="cite_ref-Rossby_7-0" class="reference"><a href="#cite_note-Rossby-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> These undulations give the hollows and peaks of altitude. In general, absolute <a href="/wiki/Positive_vorticity_advection" title="Positive vorticity advection">vorticity advection is positive</a> between these two features, but closer to the ridge, whereas it is negative just behind a trough. </p><p>At the surface, lifting air under positive vorticity advection is reflected by the formation of depressions and troughs. There will therefore be a slope between the barometric high altitude and that on the ground, this slope going towards the mass of cold air at high altitude (generally towards the Pole). </p> <div class="mw-heading mw-heading3"><h3 id="Positively/negatively_tilted"><span id="Positively.2Fnegatively_tilted"></span>Positively/negatively tilted</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Trough_(meteorology)&action=edit&section=3" title="Edit section: Positively/negatively tilted"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Troughs have an orientation relative to the poles which is rarely North-South. In the Northern Hemisphere, positively tilted troughs will extend from the lowest pressure northeast to southwest while negatively tilted troughs have a northwest to southeast orientation.<sup id="cite_ref-tilt_8-0" class="reference"><a href="#cite_note-tilt-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> In the Southern Hemisphere, the positive tilt will be southeast to northwest and the negative one southwest to northeast. </p><p>A trough will usually begin with a positive tilt as cold air moves toward the Equator.<sup id="cite_ref-tilt_8-1" class="reference"><a href="#cite_note-tilt-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> The trough will become neutral (North-South) and then negatively tilted as the energy carried by the cold air races east through the atmospheric circulation and distorts its shape.<sup id="cite_ref-tilt_8-2" class="reference"><a href="#cite_note-tilt-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> The positive tilt is thus the building phase of the trough and the negative tilt is the dissipation of its energy. Therefore, the clouds and precipitation will develop in the positive phase and the most severe weather will be in the negative phase.<sup id="cite_ref-tilt_8-3" class="reference"><a href="#cite_note-tilt-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Types_of_trough">Types of trough</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Trough_(meteorology)&action=edit&section=4" title="Edit section: Types of trough"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>In addition to standard troughs, some troughs may be described further with a qualifying term indicating a specific or a set of characteristics. </p> <div class="mw-heading mw-heading3"><h3 id="Inverted_trough">Inverted trough</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Trough_(meteorology)&action=edit&section=5" title="Edit section: Inverted trough"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>An inverted trough is an atmospheric trough which is oriented opposite to most troughs of the mid-latitudes. Most (but not all) inverted troughs are <a href="/wiki/Tropical_waves" class="mw-redirect" title="Tropical waves">tropical waves</a> (also commonly called easterly waves). </p><p>Most troughs of low pressure in the mid-latitudes of the Northern Hemisphere are characterized by decreasing atmospheric pressure from south to north while inverted troughs are characterized by decreasing pressure from north to south. This situation is the opposite in the Southern Hemisphere. Inverted troughs in both hemispheres move to the west from the east, while mid-latitude troughs generally move with the <a href="/wiki/Westerlies" title="Westerlies">westerlies</a> toward the east. </p> <div class="mw-heading mw-heading3"><h3 id="Lee_trough">Lee trough</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Trough_(meteorology)&action=edit&section=6" title="Edit section: Lee trough"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>A lee trough, also known as a dynamic trough, is "A pressure trough formed on the lee side of a mountain range in situations where the wind is blowing with a substantial component across the mountain ridge; often seen on United States weather maps east of the Rocky Mountains, and sometimes east of the Appalachians, where it is less pronounced."<sup id="cite_ref-LeeTroughDef_9-0" class="reference"><a href="#cite_note-LeeTroughDef-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> It can be formed either as a result of the <a href="/wiki/Adiabatic_process" title="Adiabatic process">adiabatic</a> compression of sinking air on the lee side of a mountain range, or through <a href="/wiki/Cyclogenesis" title="Cyclogenesis">cyclogenesis</a> resulting from "the horizontal convergence associated with vertical stretching of air columns passing over the ridge and descending the lee slope."<sup id="cite_ref-LeeTroughDef_9-1" class="reference"><a href="#cite_note-LeeTroughDef-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-LeeSideTroughLow_10-0" class="reference"><a href="#cite_note-LeeSideTroughLow-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Weather_associated">Weather associated</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Trough_(meteorology)&action=edit&section=7" title="Edit section: Weather associated"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><a href="/wiki/Convection_cell" title="Convection cell">Convective cells</a> may develop in the vicinity of troughs and give birth to a <a href="/wiki/Tropical_cyclone" title="Tropical cyclone">tropical cyclone</a>. Some tropical or subtropical regions such as the <a href="/wiki/Philippines" title="Philippines">Philippines</a> or <a href="/wiki/South_China" title="South China">South China</a> are greatly affected by convection cells along a trough. </p><p>In the mid-latitude <a href="/wiki/Westerlies" title="Westerlies">westerlies</a>, upper level troughs and <a href="/wiki/Ridge_(meteorology)" title="Ridge (meteorology)">ridges</a> often alternate in a high-amplitude pattern. For a trough in the westerlies, the region just west of the trough axis is typically an area of convergent winds and descending air – and hence high pressure –, while the region just east of the trough axis is an area of fast, divergent winds and low pressure. <a href="/wiki/Tropical_wave" title="Tropical wave">Tropical waves</a> are a type of trough in easterly currents, a <a href="/wiki/Cyclone" title="Cyclone">cyclonic</a> northward deflection of the trade winds. </p> <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Trough_(meteorology)&action=edit&section=8" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/Asiatic_low" class="mw-redirect" title="Asiatic low">Asiatic low</a></li> <li><a href="/wiki/Geopotential_height" title="Geopotential height">Geopotential height</a></li> <li><a href="/wiki/Surface_weather_analysis" title="Surface weather analysis">Surface weather analysis</a></li></ul> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Trough_(meteorology)&action=edit&section=9" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns 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Retrieved <span class="nowrap">2006-05-28</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Archived+copy&rft_id=http%3A%2F%2Fwww.met.gov.fj%2Faifs_prods%2F0640.gif&rfr_id=info%3Asid%2Fen.wikipedia.org%3ATrough+%28meteorology%29" class="Z3988"></span><span class="cs1-maint citation-comment"><code class="cs1-code">{{<a href="/wiki/Template:Cite_web" title="Template:Cite web">cite web</a>}}</code>: CS1 maint: archived copy as title (<a href="/wiki/Category:CS1_maint:_archived_copy_as_title" title="Category:CS1 maint: archived copy as title">link</a>)</span></span> </li> <li id="cite_note-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-3">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.hko.gov.hk/wxinfo/currwx/flw_description/image/trough2.png">"Archived copy"</a>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20051031084856/http://www.hko.gov.hk/wxinfo/currwx/flw_description/image/trough2.png">Archived</a> from the original on 2005-10-31<span class="reference-accessdate">. Retrieved <span class="nowrap">2005-10-13</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Archived+copy&rft_id=http%3A%2F%2Fwww.hko.gov.hk%2Fwxinfo%2Fcurrwx%2Fflw_description%2Fimage%2Ftrough2.png&rfr_id=info%3Asid%2Fen.wikipedia.org%3ATrough+%28meteorology%29" class="Z3988"></span><span class="cs1-maint citation-comment"><code class="cs1-code">{{<a href="/wiki/Template:Cite_web" title="Template:Cite web">cite web</a>}}</code>: CS1 maint: archived copy as title (<a href="/wiki/Category:CS1_maint:_archived_copy_as_title" title="Category:CS1 maint: archived copy as title">link</a>)</span></span> </li> <li id="cite_note-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-4">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.hko.gov.hk/wxinfo/currwx/flw_description/image/trough3.png">"Archived copy"</a>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20051031084853/http://www.hko.gov.hk/wxinfo/currwx/flw_description/image/trough3.png">Archived</a> from the original on 2005-10-31<span class="reference-accessdate">. Retrieved <span class="nowrap">2005-10-13</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Archived+copy&rft_id=http%3A%2F%2Fwww.hko.gov.hk%2Fwxinfo%2Fcurrwx%2Fflw_description%2Fimage%2Ftrough3.png&rfr_id=info%3Asid%2Fen.wikipedia.org%3ATrough+%28meteorology%29" class="Z3988"></span><span class="cs1-maint citation-comment"><code class="cs1-code">{{<a href="/wiki/Template:Cite_web" title="Template:Cite web">cite web</a>}}</code>: CS1 maint: archived copy as title (<a href="/wiki/Category:CS1_maint:_archived_copy_as_title" title="Category:CS1 maint: archived copy as title">link</a>)</span></span> </li> <li id="cite_note-5"><span class="mw-cite-backlink"><b><a href="#cite_ref-5">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="http://www.smg.gov.mo/dm/wxChart/e_chartindex.php">Weather Chart</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20050829081838/http://www.smg.gov.mo/dm/wxChart/e_chartindex.php">Archived</a> 2005-08-29 at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a></span> </li> <li id="cite_note-6"><span class="mw-cite-backlink"><b><a href="#cite_ref-6">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.bom.gov.au/australia/charts/synoptic_col.shtml">"Latest Colour Mean Sea-Level Pressure Analysis"</a>. <i>www.bom.gov.au</i>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20180312230056/http://www.bom.gov.au/australia/charts/synoptic_col.shtml">Archived</a> from the original on 12 March 2018<span class="reference-accessdate">. Retrieved <span class="nowrap">30 April</span> 2018</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=www.bom.gov.au&rft.atitle=Latest+Colour+Mean+Sea-Level+Pressure+Analysis&rft_id=http%3A%2F%2Fwww.bom.gov.au%2Faustralia%2Fcharts%2Fsynoptic_col.shtml&rfr_id=info%3Asid%2Fen.wikipedia.org%3ATrough+%28meteorology%29" class="Z3988"></span></span> </li> <li id="cite_note-Rossby-7"><span class="mw-cite-backlink"><b><a href="#cite_ref-Rossby_7-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.weather.gov/jetstream/longshort">"Long and Short Waves"</a>. <i>JetStream</i>. <a href="/wiki/National_Weather_Service" title="National Weather Service">National Weather Service</a><span class="reference-accessdate">. Retrieved <span class="nowrap">July 29,</span> 2018</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=JetStream&rft.atitle=Long+and+Short+Waves&rft_id=https%3A%2F%2Fwww.weather.gov%2Fjetstream%2Flongshort&rfr_id=info%3Asid%2Fen.wikipedia.org%3ATrough+%28meteorology%29" class="Z3988"></span></span> </li> <li id="cite_note-tilt-8"><span class="mw-cite-backlink">^ <a href="#cite_ref-tilt_8-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-tilt_8-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-tilt_8-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-tilt_8-3"><sup><i><b>d</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.weather.gov/jetstream/basic">"Basic Wave Patterns"</a>. <i>JetStream</i>. <a href="/wiki/National_Weather_Service" title="National Weather Service">National Weather Service</a><span class="reference-accessdate">. Retrieved <span class="nowrap">July 29,</span> 2018</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=JetStream&rft.atitle=Basic+Wave+Patterns&rft_id=https%3A%2F%2Fwww.weather.gov%2Fjetstream%2Fbasic&rfr_id=info%3Asid%2Fen.wikipedia.org%3ATrough+%28meteorology%29" class="Z3988"></span></span> </li> <li id="cite_note-LeeTroughDef-9"><span class="mw-cite-backlink">^ <a href="#cite_ref-LeeTroughDef_9-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-LeeTroughDef_9-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://glossary.ametsoc.org/wiki/Lee_trough">"Lee trough"</a>. <i>Glossary of Meteorology</i> (2nd ed.). American Meteorological Society. 25 April 2012. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20170305113935/http://glossary.ametsoc.org/wiki/Lee_trough">Archived</a> from the original on 5 March 2017<span class="reference-accessdate">. Retrieved <span class="nowrap">2017-03-05</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Glossary+of+Meteorology&rft.atitle=Lee+trough&rft.date=2012-04-25&rft_id=http%3A%2F%2Fglossary.ametsoc.org%2Fwiki%2FLee_trough&rfr_id=info%3Asid%2Fen.wikipedia.org%3ATrough+%28meteorology%29" class="Z3988"></span></span> </li> <li id="cite_note-LeeSideTroughLow-10"><span class="mw-cite-backlink"><b><a href="#cite_ref-LeeSideTroughLow_10-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFJeff_Haby" class="citation web cs1">Jeff Haby. <a rel="nofollow" class="external text" href="http://www.theweatherprediction.com/habyhints/129/">"What is a Lee-side Trough (Low)?"</a>. TheWeatherPrediction.com. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20120206130043/http://www.theweatherprediction.com/habyhints/129/">Archived</a> from the original on 2012-02-06<span class="reference-accessdate">. Retrieved <span class="nowrap">2006-10-30</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=What+is+a+Lee-side+Trough+%28Low%29%3F&rft.pub=TheWeatherPrediction.com&rft.au=Jeff+Haby&rft_id=http%3A%2F%2Fwww.theweatherprediction.com%2Fhabyhints%2F129%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3ATrough+%28meteorology%29" class="Z3988"></span></span> </li> </ol></div>    </div><noscript><img src="https://login.wikimedia.org/wiki/Special:CentralAutoLogin/start?type=1x1" alt="" width="1" height="1" style="border: none; position: absolute;"></noscript> <div class="printfooter" data-nosnippet="">Retrieved from "<a dir="ltr" href="https://en.wikipedia.org/w/index.php?title=Trough_(meteorology)&oldid=1248454276">https://en.wikipedia.org/w/index.php?title=Trough_(meteorology)&oldid=1248454276</a>"</div></div> <div id="catlinks" class="catlinks" data-mw="interface"><div id="mw-normal-catlinks" class="mw-normal-catlinks"><a href="/wiki/Help:Category" title="Help:Category">Categories</a>: <ul><li><a href="/wiki/Category:Atmospheric_dynamics" title="Category:Atmospheric dynamics">Atmospheric dynamics</a></li><li><a href="/wiki/Category:Atmospheric_circulation" title="Category:Atmospheric circulation">Atmospheric circulation</a></li><li><a href="/wiki/Category:Synoptic_meteorology_and_weather" title="Category:Synoptic meteorology and weather">Synoptic meteorology and weather</a></li></ul></div><div id="mw-hidden-catlinks" class="mw-hidden-catlinks mw-hidden-cats-hidden">Hidden categories: <ul><li><a href="/wiki/Category:Webarchive_template_wayback_links" title="Category:Webarchive template wayback links">Webarchive template wayback links</a></li><li><a href="/wiki/Category:CS1_maint:_archived_copy_as_title" title="Category:CS1 maint: archived copy as title">CS1 maint: archived copy as title</a></li><li><a href="/wiki/Category:Articles_with_short_description" title="Category:Articles with short description">Articles with short description</a></li><li><a href="/wiki/Category:Short_description_matches_Wikidata" title="Category:Short description matches Wikidata">Short description matches Wikidata</a></li></ul></div></div> </div> </main> </div> <div class="mw-footer-container"> <footer id="footer" class="mw-footer" > <ul id="footer-info"> <li id="footer-info-lastmod"> This page was last edited on 29 September 2024, at 16:10<span class="anonymous-show"> (UTC)</span>.</li> <li id="footer-info-copyright">Text is available under the <a href="/wiki/Wikipedia:Text_of_the_Creative_Commons_Attribution-ShareAlike_4.0_International_License" title="Wikipedia:Text of the Creative Commons Attribution-ShareAlike 4.0 International License">Creative Commons Attribution-ShareAlike 4.0 License</a>; additional terms may apply. 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