{"id":9814,"date":"2024-07-30T11:15:39","date_gmt":"2024-07-30T11:15:39","guid":{"rendered":"https:\/\/www.nextias.com\/blog\/?p=9814"},"modified":"2024-07-31T12:53:25","modified_gmt":"2024-07-31T12:53:25","slug":"southwest-monsoon-in-india","status":"publish","type":"post","link":"https:\/\/www.nextias.com\/blog\/southwest-monsoon-in-india\/","title":{"rendered":"SouthWest Monsoon in India: Features, Theories &amp; Mechanism"},"content":{"rendered":"\n<p><em>The <strong>SouthWest Monsoon in India<\/strong> is a major seasonal wind system that brings substantial rainfall to the Indian subcontinent from June to September. Its significance lies in its critical role in replenishing water resources and supporting agriculture across the region. This article aims to study in detail the characteristics, impacts, and mechanisms of the Southwest Monsoon, along with the various theories that explain its behaviour.<\/em><\/p><div id=\"ez-toc-container\" class=\"ez-toc-v2_0_56_1 counter-hierarchy ez-toc-counter ez-toc-transparent ez-toc-container-direction\">\n<div class=\"ez-toc-title-container\">\n<span class=\"ez-toc-title-toggle\"><\/span><\/div>\n<nav><ul class='ez-toc-list ez-toc-list-level-1 ' ><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/www.nextias.com\/blog\/southwest-monsoon-in-india\/#About_Indian_Monsoon\" title=\"About Indian Monsoon\">About Indian Monsoon<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/www.nextias.com\/blog\/southwest-monsoon-in-india\/#About_SouthWest_Monsoon_Season\" title=\"About SouthWest Monsoon Season\">About SouthWest Monsoon Season<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/www.nextias.com\/blog\/southwest-monsoon-in-india\/#Features_of_SouthWest_Monsoon\" title=\"Features of SouthWest Monsoon\">Features of SouthWest Monsoon<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/www.nextias.com\/blog\/southwest-monsoon-in-india\/#Theories_for_Prediction_of_Indian_Monsoon\" title=\"Theories for Prediction of Indian Monsoon\">Theories for Prediction of Indian Monsoon<\/a><ul class='ez-toc-list-level-3'><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/www.nextias.com\/blog\/southwest-monsoon-in-india\/#The_Thermal_Theory\" title=\"The Thermal Theory\">The Thermal Theory<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"https:\/\/www.nextias.com\/blog\/southwest-monsoon-in-india\/#The_Equatorial_Westerly_Theory\" title=\"The Equatorial Westerly Theory\">The Equatorial Westerly Theory<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-7\" href=\"https:\/\/www.nextias.com\/blog\/southwest-monsoon-in-india\/#The_Jet_Stream_Theory\" title=\"The Jet Stream Theory\">The Jet Stream Theory<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-8\" href=\"https:\/\/www.nextias.com\/blog\/southwest-monsoon-in-india\/#The_El-Nino_Theory\" title=\"The El-Nino Theory\">The El-Nino Theory<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-9\" href=\"https:\/\/www.nextias.com\/blog\/southwest-monsoon-in-india\/#Conditions_during_South_West_Monsoon\" title=\"Conditions during South West Monsoon\">Conditions during South West Monsoon<\/a><ul class='ez-toc-list-level-3'><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-10\" href=\"https:\/\/www.nextias.com\/blog\/southwest-monsoon-in-india\/#Temperature\" title=\"Temperature\">Temperature<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-11\" href=\"https:\/\/www.nextias.com\/blog\/southwest-monsoon-in-india\/#Pressure_and_Winds\" title=\"Pressure and Winds\">Pressure and Winds<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-12\" href=\"https:\/\/www.nextias.com\/blog\/southwest-monsoon-in-india\/#Rainfall\" title=\"Rainfall\">Rainfall<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-13\" href=\"https:\/\/www.nextias.com\/blog\/southwest-monsoon-in-india\/#Mechanism_of_South_West_Monsoon\" title=\"Mechanism of South West Monsoon\">Mechanism of South West Monsoon<\/a><ul class='ez-toc-list-level-3'><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-14\" href=\"https:\/\/www.nextias.com\/blog\/southwest-monsoon-in-india\/#Monsoon_Winds_of_Arabian_Sea\" title=\"Monsoon Winds of Arabian Sea\">Monsoon Winds of Arabian Sea<\/a><ul class='ez-toc-list-level-4'><li class='ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-15\" href=\"https:\/\/www.nextias.com\/blog\/southwest-monsoon-in-india\/#First_Branch\" title=\"First Branch\">First Branch<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-16\" href=\"https:\/\/www.nextias.com\/blog\/southwest-monsoon-in-india\/#Second_Branch\" title=\"Second Branch\">Second Branch<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-17\" href=\"https:\/\/www.nextias.com\/blog\/southwest-monsoon-in-india\/#Third_Branch\" title=\"Third Branch\">Third Branch<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-18\" href=\"https:\/\/www.nextias.com\/blog\/southwest-monsoon-in-india\/#Monsoon_Winds_of_Bay_of_Bengal\" title=\"Monsoon Winds of Bay of Bengal\">Monsoon Winds of Bay of Bengal<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-19\" href=\"https:\/\/www.nextias.com\/blog\/southwest-monsoon-in-india\/#Conclusion\" title=\"Conclusion\">Conclusion<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-20\" href=\"https:\/\/www.nextias.com\/blog\/southwest-monsoon-in-india\/#Difference_between_South_West_Monsoon_and_North_East_Monsoon\" title=\"Difference between South West Monsoon and North East Monsoon\">Difference between South West Monsoon and North East Monsoon<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-21\" href=\"https:\/\/www.nextias.com\/blog\/southwest-monsoon-in-india\/#Frequently_Asked_Questions_FAQs\" title=\"Frequently Asked Questions (FAQs)\">Frequently Asked Questions (FAQs)<\/a><ul class='ez-toc-list-level-3'><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-22\" href=\"https:\/\/www.nextias.com\/blog\/southwest-monsoon-in-india\/#What_is_the_South_West_Monsoon\" title=\"What is the South West Monsoon?\">What is the South West Monsoon?<\/a><\/li><\/ul><\/li><\/ul><\/nav><\/div>\n\n\n\n\n<h2 class=\"wp-block-heading has-text-color has-link-color wp-elements-70ed0544ecd1846e4a4e6801c6bd7590\" style=\"color:#015aa7\"><span class=\"ez-toc-section\" id=\"About_Indian_Monsoon\"><\/span><strong>About Indian Monsoon<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li>The Indian Monsoon is a critical climatic phenomenon characterised by seasonal wind shifts that bring heavy rains to the Indian subcontinent.<\/li>\n\n\n\n<li>The Southwest Monsoon typically begins in June, bringing moisture-laden winds from the Indian Ocean, and continues until September.<\/li>\n\n\n\n<li>The Northeast Monsoon, occurring from October to December, affects southeastern India.<\/li>\n<\/ul>\n\n\n\n<p>Read our detailed article on the <a href=\"https:\/\/www.nextias.com\/blog\/monsoon-in-india\/\"><strong>Monsoon in India.<\/strong><\/a><\/p>\n\n\n\n<h2 class=\"wp-block-heading has-text-color has-link-color wp-elements-4f864261165d9683725801ee9c07acd4\" style=\"color:#015aa7\"><span class=\"ez-toc-section\" id=\"About_SouthWest_Monsoon_Season\"><\/span><strong>About SouthWest Monsoon Season<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li>The South West Monsoon is a major seasonal wind system that brings substantial rainfall to the Indian subcontinent.<\/li>\n\n\n\n<li>It typically begins in June and lasts until September, driven by moisture-laden winds from the Indian Ocean.<\/li>\n\n\n\n<li>The monsoon is characterised by heavy rains and is crucial for agriculture and water resources in India.<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading has-text-color has-link-color wp-elements-8f10fbd721ee348b36f07cb23f9fc403\" style=\"color:#015aa7\"><span class=\"ez-toc-section\" id=\"Features_of_SouthWest_Monsoon\"><\/span><strong>Features of SouthWest Monsoon<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>These winds generally strike the Indian coast in the<strong> first week of June.<\/strong> However, their <strong>arrival and departure<\/strong> may be <strong>before time<\/strong> or even <strong>delayed<\/strong>.<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>There may be <strong>dry spells <\/strong>between rainy periods, leading to <strong>crop failure.<\/strong><\/li>\n\n\n\n<li>At times, these winds may <strong>skip over certain regions<\/strong> without any apparent cause.<\/li>\n\n\n\n<li>The <strong>amount and timing of rainfall<\/strong> and the intervals of <strong>wet and dry spells <\/strong>vary yearly, a phenomenon known as the <strong>vagaries of the monsoons.<\/strong><\/li>\n\n\n\n<li>The <strong>spatial distribution of rainfall<\/strong> is uneven: some regions may experience <strong>heavy rains,<\/strong> while others receive <strong>meagre or scanty rainfall.<\/strong><\/li>\n\n\n\n<li>Typically, these winds begin <strong>retreating by the end of September,<\/strong> but their<strong> departure may sometimes be delayed until October.<\/strong><\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading has-text-color has-link-color wp-elements-3a169a48c16e22ea9308c005fcd0b5fc\" style=\"color:#015aa7\"><span class=\"ez-toc-section\" id=\"Theories_for_Prediction_of_Indian_Monsoon\"><\/span><strong>Theories for Prediction of Indian Monsoon<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>There are several theories for the prediction of the Indian Monsoon:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>The Thermal Theory,<\/li>\n\n\n\n<li>The Equatorial Westerly Theory,<\/li>\n\n\n\n<li>The Jet Stream Theory, and<\/li>\n\n\n\n<li>The El- Nino Theory.<\/li>\n<\/ul>\n\n\n\n<p class=\"has-text-align-center\">All these theories have been discussed in detail in the following section.<\/p>\n\n\n\n<h3 class=\"wp-block-heading has-text-color has-link-color wp-elements-920cf9c733a4d08142a46cb9c7040274\" style=\"color:#ff6a00\"><span class=\"ez-toc-section\" id=\"The_Thermal_Theory\"><\/span><strong>The Thermal Theory<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>According to the <strong>thermal theory,<\/strong> temperature is the main reason for the origin of the monsoons.<\/li>\n\n\n\n<li>In summer, <strong>sun rays cause greater low pressure, <\/strong>which results in the absence of <strong>north-east trade wind.<\/strong><\/li>\n\n\n\n<li>According to <strong>Ferrell\u2019s rules, <\/strong>these winds turn towards their right (northeast) when they come in the northern hemisphere and blow on the whole Indian peninsula.<\/li>\n\n\n\n<li>These winds are full of moisture. They bring rainfall over the Indian peninsula by dividing it into two branches.<\/li>\n\n\n\n<li>Heavy rainfall occurs on the <strong>western slope of the Western Ghats<\/strong> by the Arabian Sea branch, and <strong>Andaman and Nicobar Islands<\/strong> and <strong>northeast India<\/strong> by the Bay of Bengal branch.<\/li>\n\n\n\n<li>The Bay of Bengal branch moves towards the <strong>low-pressure areas of northwest India.<\/strong><\/li>\n\n\n\n<li>The amount of rainfall keeps becoming less because of a shortage of water vapour when it moves from east to west.<\/li>\n\n\n\n<li>In winter, the <strong>northeast trade wind<\/strong> once again begins to blow.\n<ul class=\"wp-block-list\">\n<li>They bring the<strong> northeast monsoon<\/strong> and cause rainfall on the <strong>coast of Tamil Nadu<\/strong> after getting water vapour from the Bay of Bengal.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading has-text-color has-link-color wp-elements-32730dea56023599e2ebc37f57512239\" style=\"color:#ff6a00\"><span class=\"ez-toc-section\" id=\"The_Equatorial_Westerly_Theory\"><\/span><strong>The Equatorial Westerly Theory<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>The Equatorial Westerly Theory was <strong>propounded by Flohn.<\/strong>\n<ul class=\"wp-block-list\">\n<li>According to him, the equatorial westerly is the south west monsoon.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li>It originated because of <strong>inter-tropical convergence.<\/strong>\n<ul class=\"wp-block-list\">\n<li>He also considered the <strong>thermal effect to be the main reason<\/strong> for the origin of monsoons.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li>In the summer, the ITCZ happen in the north of the equator because of the northern movement of the thermal equator.<\/li>\n\n\n\n<li>The equatorial westerly now begins blowing toward the low pressure created on the Indian Peninsula; it is the <strong>SouthWest Monsoon.<\/strong><\/li>\n\n\n\n<li>The ITCZ is known as the<strong> Monsoon Trough<\/strong>.<\/li>\n\n\n\n<li>In winter, the area of low pressure changes into high pressure because of the winter solstice and northeast trade winds once again become active.<\/li>\n<\/ul>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"385\" height=\"235\" src=\"https:\/\/wp-images.nextias.com\/cdn-cgi\/image\/format=auto\/blog\/uploads\/2024\/07\/1-7.png\" alt=\"SouthWest Monsoon in India\" class=\"wp-image-9826\" srcset=\"https:\/\/wp-images.nextias.com\/cdn-cgi\/image\/format=auto\/blog\/uploads\/2024\/07\/1-7.png 385w, https:\/\/wp-images.nextias.com\/cdn-cgi\/image\/format=auto\/blog\/uploads\/2024\/07\/1-7-150x92.png 150w\" sizes=\"auto, (max-width: 385px) 100vw, 385px\" \/><\/figure>\n\n\n\n<h3 class=\"wp-block-heading has-text-color has-link-color wp-elements-48ca504c35f7cd515dcaf9ca78e21088\" style=\"color:#ff6a00\"><span class=\"ez-toc-section\" id=\"The_Jet_Stream_Theory\"><\/span><strong>The Jet Stream Theory<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>The Jet Stream theory was <strong>propounded by Yest. <\/strong>The jet stream is a very fast-blowing current system in the upper atmosphere (9 to 18 km), and its speed is maximum in the middle part (340 km\/hr).<\/li>\n\n\n\n<li>This system works as a cover over Earth, which affects the weather in the lower atmosphere.<\/li>\n\n\n\n<li>The south east monsoon in India is related to the <strong>tropical easterly jet stream,<\/strong> which blows between 80 N and 350 N latitude.<\/li>\n\n\n\n<li>The northeast (winter monsoon) is associated with the subtropical westerly jet stream, which blows between 20\u00b0 and 30\u00b0 latitude in both hemispheres.<\/li>\n\n\n\n<li>In the winter, the subtropical westerly jet stream blows from west to east over <strong>West and Middle Asia.<\/strong><\/li>\n\n\n\n<li>The Tibetan plateau is divided into two parts, creating hurdles in its way. One branch began to blow <strong>parallel to the plateau from the north, <\/strong>and another moved towards the <strong>east in the south of the Himalayas.<\/strong><\/li>\n\n\n\n<li>The mean position of these branches was roughly between 25\u00b0N latitude in February.<\/li>\n\n\n\n<li>The <strong>western disturbances<\/strong> that enter the Indian subcontinent in winter are brought by the westerly jet stream.\n<ul class=\"wp-block-list\">\n<li>This disturbance generally occurs before westerly jet streams.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li>The westerly jet stream is a column of cold wind that pushes downwind to the surface, creating high pressure on the surface.<\/li>\n\n\n\n<li>The dry wind from this high-pressure area (the northwest part of India) begins blowing towards a low-pressure area (the Bay of Bengal).\n<ul class=\"wp-block-list\">\n<li>This wind brings cold winds in winter to Uttar Pradesh and Bihar.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li>After reaching the Bay of Bengal, this wind, following <strong>Ferrell\u2019s rules, <\/strong>becomes a northeast monsoon.<\/li>\n\n\n\n<li>When this monsoon wind reaches the coast of Tamil Nadu, it causes rainfall with humidity received from the Bay of Bengal.<\/li>\n\n\n\n<li>The summer westerly jet stream does not blow over the Indian subcontinent. It transits towards the north of the Tibetan plateau.<\/li>\n\n\n\n<li>At this time, the<strong> tropical easterly jet stream <\/strong>blows into India&#8217;s upper atmosphere (the upper parts of the troposphere).<\/li>\n\n\n\n<li>The Tibetan plateau and central Asia becoming too hot is considered a reason for its origin.<\/li>\n\n\n\n<li>The <strong>clockwise cyclic circulation<\/strong> in the middle of the troposphere begins with the winds rising from the plateau of Tibet after becoming hot.<\/li>\n\n\n\n<li>This going upward air divides itself into<strong> two separate streams near the tropopause.<\/strong><\/li>\n\n\n\n<li>One of these blows is in the form of easterly jet streams toward the equator, and the other blow is in the form of westerly jet streams toward the pole.<\/li>\n\n\n\n<li>It is to be noted that a westerly jet stream keeps blowing in central Asia in summer.<\/li>\n\n\n\n<li>The easterly jet streams begin to settle in the Arabian Sea by blowing towards the southwest direction in the upper atmosphere.\n<ul class=\"wp-block-list\">\n<li>It creates a very <strong>high-pressure belt over there.<\/strong><\/li>\n<\/ul>\n<\/li>\n\n\n\n<li>Inversely when this hot jet stream blows over the Indian subcontinent, it pulls up the surface air and creates a very low pressure.<\/li>\n\n\n\n<li>To fill this low pressure, winds from a high-pressure area of the Arabian Sea begin to blow towards the northeast.\n<ul class=\"wp-block-list\">\n<li>This is known as the <strong>SouthWest Monsoon.<\/strong><\/li>\n<\/ul>\n<\/li>\n<\/ul>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"389\" height=\"267\" src=\"https:\/\/wp-images.nextias.com\/cdn-cgi\/image\/format=auto\/blog\/uploads\/2024\/07\/2-5.png\" alt=\"SouthWest Monsoon\" class=\"wp-image-9827\" srcset=\"https:\/\/wp-images.nextias.com\/cdn-cgi\/image\/format=auto\/blog\/uploads\/2024\/07\/2-5.png 389w, https:\/\/wp-images.nextias.com\/cdn-cgi\/image\/format=auto\/blog\/uploads\/2024\/07\/2-5-376x258.png 376w, https:\/\/wp-images.nextias.com\/cdn-cgi\/image\/format=auto\/blog\/uploads\/2024\/07\/2-5-218x150.png 218w, https:\/\/wp-images.nextias.com\/cdn-cgi\/image\/format=auto\/blog\/uploads\/2024\/07\/2-5-100x70.png 100w, https:\/\/wp-images.nextias.com\/cdn-cgi\/image\/format=auto\/blog\/uploads\/2024\/07\/2-5-150x103.png 150w\" sizes=\"auto, (max-width: 389px) 100vw, 389px\" \/><\/figure>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-background has-fixed-layout\" style=\"background-color:#ebecf0\"><tbody><tr><td><strong>Note:<\/strong> However, studies show this easterly jet stream is only seasonal. When it blows for an extended period over a large area in India, it causes floods, and when it weakens, it causes droughts. This theory <strong>does not explain<\/strong> why easterly jet streams are so much indefinite.<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"457\" height=\"497\" src=\"https:\/\/wp-images.nextias.com\/cdn-cgi\/image\/format=auto\/blog\/uploads\/2024\/07\/3-3.png\" alt=\"Indian Monsoon\" class=\"wp-image-9828\" srcset=\"https:\/\/wp-images.nextias.com\/cdn-cgi\/image\/format=auto\/blog\/uploads\/2024\/07\/3-3.png 457w, https:\/\/wp-images.nextias.com\/cdn-cgi\/image\/format=auto\/blog\/uploads\/2024\/07\/3-3-237x258.png 237w, https:\/\/wp-images.nextias.com\/cdn-cgi\/image\/format=auto\/blog\/uploads\/2024\/07\/3-3-386x420.png 386w, https:\/\/wp-images.nextias.com\/cdn-cgi\/image\/format=auto\/blog\/uploads\/2024\/07\/3-3-150x163.png 150w\" sizes=\"auto, (max-width: 457px) 100vw, 457px\" \/><\/figure>\n\n\n\n<h3 class=\"wp-block-heading has-text-color has-link-color wp-elements-4dacb76c9ed7923597d4cb0bce4b396c\" style=\"color:#ff6a00\"><span class=\"ez-toc-section\" id=\"The_El-Nino_Theory\"><\/span><strong>The El-Nino Theory<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>El-Nino<\/strong> is characterised by subsurface warm ocean currents flowing north to south along the Peruvian coast.<\/li>\n\n\n\n<li>American scientist <strong>Gilbert Walker initially studied it,<\/strong> and observed that the warm water of El-Nino increases the temperature of southern equatorial warm ocean currents.<\/li>\n\n\n\n<li>This current flows east to west in the middle Pacific Ocean, warming the region and causing very low atmospheric pressure there.<\/li>\n\n\n\n<li>When this low pressure extends to the <strong>eastern central parts of the Indian Ocean,<\/strong> it alters the direction of the Indian monsoon.<\/li>\n\n\n\n<li>The low pressure over the Indian subcontinent becomes comparatively weaker than the low pressure in the Indian Ocean.<\/li>\n\n\n\n<li>Consequently, winds from high-pressure areas of the <strong>Arabian Sea<\/strong> blow towards the southeastern Indian Ocean, leading to drought in the Indian subcontinent.<\/li>\n\n\n\n<li>Conversely, if the effects of the El-Nino water current remain confined to the middle Pacific, the southwest monsoon winds remain undisturbed, resulting in sufficient rainfall in India.<\/li>\n\n\n\n<li>However, the effects of El Nino alone cannot fully explain drought conditions in India, indicating the need for further research in this area.<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading has-text-color has-link-color wp-elements-7a055b9f6c4ebfba0dfaa12215330c36\" style=\"color:#015aa7\"><span class=\"ez-toc-section\" id=\"Conditions_during_South_West_Monsoon\"><\/span><strong>Conditions during South West Monsoon<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>The southwest monsoon in India typically occurs from June to September and is characterised by several conditions:<\/p>\n\n\n\n<h3 class=\"wp-block-heading has-text-color has-link-color wp-elements-99d0da3bf5104d79ed701f793d85de33\" style=\"color:#ff6a00\"><span class=\"ez-toc-section\" id=\"Temperature\"><\/span><strong>Temperature<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Sudden Onset and Temperature Fall<\/strong> &#8211; The arrival of the southwest monsoons leads to a significant drop in temperature (3\u00b0C to 6\u00b0C).\n<ul class=\"wp-block-list\">\n<li>This temperature change varies throughout the rainy season.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Temperature Variability<\/strong> &#8211; Temperature rises in September with the cessation of the southwest monsoons.\n<ul class=\"wp-block-list\">\n<li>Breaks in the monsoons also cause temporary increases in temperature.<\/li>\n\n\n\n<li>The diurnal temperature range is small due to cloud cover and rainfall.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Regional Temperature Patterns- The highest temperatures (38\u00b0C to 40\u00b0C) are experienced west of the Aravalis<\/strong> due to a lack of clouds and hot continental air masses.\n<ul class=\"wp-block-list\">\n<li>The Western Ghats have lower temperatures due to heavy rainfall, while Tamil Nadu and adjoining Andhra Pradesh have temperatures above 30\u00b0C due to minimal rainfall.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading has-text-color has-link-color wp-elements-db2a2a060ec5d0a162fdd0e1d1221fc8\" style=\"color:#ff6a00\"><span class=\"ez-toc-section\" id=\"Pressure_and_Winds\"><\/span><strong>Pressure and Winds<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Low Pressure Conditions<\/strong> &#8211; <strong>Due to high temperatures, Low pressure prevails over northwest India,<\/strong> with the <strong>ITCZ (monsoon trough)<\/strong> lying along the <strong>Ganga plain.<\/strong>\n<ul class=\"wp-block-list\">\n<li>Its location shifts depending on weather conditions.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Wind Patterns<\/strong> &#8211; Winds blow from <strong>southwest to northeast<\/strong> due to the pressure gradient between north and south.\n<ul class=\"wp-block-list\">\n<li>In the<strong> Indo-Gangetic plain,<\/strong> winds change direction from <strong>east to west.<\/strong><\/li>\n<\/ul>\n<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading has-text-color has-link-color wp-elements-33536dd15532449e9ef560998845fa1e\" style=\"color:#ff6a00\"><span class=\"ez-toc-section\" id=\"Rainfall\"><\/span><strong>Rainfall<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Rainfall Distribution<\/strong>: The <strong>southwest monsoon<\/strong> accounts for <strong>three-fourths of India\u2019s total annual rainfall.<\/strong>\n<ul class=\"wp-block-list\">\n<li>The average rainfall over the plains during this season is about 87%.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Advance and Timing<\/strong>: The south west monsoon advances quickly with <strong>thunder, lightning, and heavy downpours.<\/strong>\n<ul class=\"wp-block-list\">\n<li>The normal arrival date is <strong>20th May in the Andaman and Nicobar Islands and 1st June in Kerala.<\/strong><\/li>\n\n\n\n<li>Delays in the south west monsoon can reduce its duration, with rainfall decreasing from <strong>south to north.<\/strong><\/li>\n<\/ul>\n<\/li>\n<\/ul>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-background has-fixed-layout\" style=\"background-color:#ebecf0\"><tbody><tr><td><strong>Variability of Rainfall<\/strong><br><br>&#8211; Rainfall variability is computed using the <strong>coefficient of variation (C.V.)<\/strong>.\u00a0<br>&#8211; Areas with <strong>less than 25% variability<\/strong> receive annual rainfall over <strong>100 cm<\/strong>, while areas with <strong>more than 50% <\/strong>have annual rainfall less than <strong>50 cm<\/strong>.\u00a0<br>&#8211; Regions with <strong>25-50% variability<\/strong> receive <strong>50-100 cm<\/strong> of annual rainfall.<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h2 class=\"wp-block-heading has-text-color has-link-color wp-elements-80646809b6f9d9598f286275fb03948c\" style=\"color:#015aa7\"><span class=\"ez-toc-section\" id=\"Mechanism_of_South_West_Monsoon\"><\/span><strong>Mechanism of South West Monsoon<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li>The <strong>Southwest Monsoon<\/strong> begins with the inflow of <strong>Southwest monsoons,<\/strong> which generally strike the coast of <strong>Kerala <\/strong>in the first week of June and cover most of India by mid-July.<\/li>\n\n\n\n<li>This weather pattern continues until September. The arrival of these <strong>warm, moisture-laden winds<\/strong> brings a significant change in weather conditions, causing <strong>sudden rains<\/strong> that reduce temperatures by<strong> 5\u00b0C to 10\u00b0C.<\/strong><\/li>\n\n\n\n<li>This sudden onset of rain is called a <strong>break of monsoons or a burst of monsoons.<\/strong><\/li>\n\n\n\n<li>Depending on the pressure conditions over the <strong>northern plains<\/strong> and the <strong>Indian Ocean, the arrival of these winds may be delayed by a week or two.<\/strong><\/li>\n\n\n\n<li>The peninsular shape of India divides these Southwest monsoons into two branches:\n<ul class=\"wp-block-list\">\n<li>The <strong>Arabian Sea branch<\/strong> and<\/li>\n\n\n\n<li>The <strong>Bay of Bengal branch.<\/strong><\/li>\n<\/ul>\n<\/li>\n<\/ul>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"450\" height=\"554\" src=\"https:\/\/wp-images.nextias.com\/cdn-cgi\/image\/format=auto\/blog\/uploads\/2024\/07\/4-2.png\" alt=\"SouthWest Monsoon in India\" class=\"wp-image-9829\" srcset=\"https:\/\/wp-images.nextias.com\/cdn-cgi\/image\/format=auto\/blog\/uploads\/2024\/07\/4-2.png 450w, https:\/\/wp-images.nextias.com\/cdn-cgi\/image\/format=auto\/blog\/uploads\/2024\/07\/4-2-210x258.png 210w, https:\/\/wp-images.nextias.com\/cdn-cgi\/image\/format=auto\/blog\/uploads\/2024\/07\/4-2-324x400.png 324w, https:\/\/wp-images.nextias.com\/cdn-cgi\/image\/format=auto\/blog\/uploads\/2024\/07\/4-2-341x420.png 341w, https:\/\/wp-images.nextias.com\/cdn-cgi\/image\/format=auto\/blog\/uploads\/2024\/07\/4-2-150x185.png 150w\" sizes=\"auto, (max-width: 450px) 100vw, 450px\" \/><\/figure>\n\n\n\n<h3 class=\"wp-block-heading has-text-color has-link-color wp-elements-80649f96fccb3c5a4f22649a46865a30\" style=\"color:#ff6a00\"><span class=\"ez-toc-section\" id=\"Monsoon_Winds_of_Arabian_Sea\"><\/span><strong>Monsoon Winds of Arabian Sea<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p>The Southwest monsoon winds originating over the Arabian Sea further split into three branches:<\/p>\n\n\n\n<h4 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"First_Branch\"><\/span><strong>First Branch<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n\n<ul class=\"wp-block-list\">\n<li>The <strong>first branch<\/strong> of the <strong>Arabian Sea monsoon<\/strong> is blocked by the <strong>Western Ghats.<\/strong><\/li>\n\n\n\n<li>As these winds ascend the slopes of the Western Ghats, at elevations of <strong>900-1200 meters,<\/strong> they cool down.<\/li>\n\n\n\n<li>Consequently, the <strong>windward side of the Sahyadris<\/strong> and the <strong>Western Coastal Plain <\/strong>receives <strong>very heavy rainfall, <\/strong>ranging from <strong>250 cm to 400 cm.<\/strong><\/li>\n\n\n\n<li>After crossing the Western Ghats, these winds descend and warm up, reducing <strong>humidity<\/strong>.<\/li>\n\n\n\n<li>This leads to<strong> little rainfall east of the Western Ghats,<\/strong> creating a <strong>rain-shadow area.<\/strong><\/li>\n<\/ul>\n\n\n\n<h4 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Second_Branch\"><\/span><strong>Second Branch<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n\n<ul class=\"wp-block-list\">\n<li>The <strong>second branch<\/strong> of the <strong>Arabian Sea Monsoon<\/strong> impacts the <strong>coast north of Mumbai.<\/strong><\/li>\n\n\n\n<li>Travelling along the <strong>Narmada and Tapi river valleys<\/strong>, these winds bring rainfall to large areas of <strong>central India.<\/strong><\/li>\n\n\n\n<li>The <strong>Chotanagpur plateau <\/strong>receives <strong>15 cm of rainfall<\/strong> from this branch.<\/li>\n\n\n\n<li>Subsequently, these winds enter the <strong>Ganga plains<\/strong> and mingle with the <strong>Bay of Bengal branch.<\/strong><\/li>\n<\/ul>\n\n\n\n<h4 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Third_Branch\"><\/span><strong>Third Branch<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n\n<ul class=\"wp-block-list\">\n<li>A <strong>third branch <\/strong>of this <strong>monsoon wind<\/strong> hits the <strong>Saurashtra Peninsula<\/strong> and <strong>Kutch<\/strong>, then moves over <strong>west Rajasthan<\/strong> and along the <strong>Aravallis<\/strong>, resulting in only <strong>scanty rainfall.<\/strong><\/li>\n\n\n\n<li>In <strong>Punjab <\/strong>and <strong>Haryana<\/strong>, it merges with the<strong> Bay of Bengal branch.<\/strong>\n<ul class=\"wp-block-list\">\n<li>Together, these branches bring rainfall to the<strong> western Himalayas.<\/strong><\/li>\n<\/ul>\n<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading has-text-color has-link-color wp-elements-8f4fb1cd78e2e0e03517f8bd9d96da48\" style=\"color:#ff6a00\"><span class=\"ez-toc-section\" id=\"Monsoon_Winds_of_Bay_of_Bengal\"><\/span><strong>Monsoon Winds of Bay of Bengal<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>The<strong> Bay of Bengal branch<\/strong> strikes the coast of <strong>Myanmar <\/strong>and part of <strong>southeast Bangladesh.<\/strong> However, the <strong>Arakan Hills<\/strong> along the coast of Myanmar deflect a significant portion of this branch towards the Indian subcontinent.<\/li>\n\n\n\n<li>Consequently, the South West Monsoon enters <strong>West Bengal <\/strong>and <strong>Bangladesh <\/strong>from the <strong>south and southeast <\/strong>rather than the south-westerly direction.<\/li>\n\n\n\n<li>From here, this branch splits into two due to the influence of the <strong>Himalayas <\/strong>and the <strong>thermal low<\/strong> in northwest India.\n<ul class=\"wp-block-list\">\n<li>One branch travels westward along the <strong>Ganga plains, <\/strong>extending to the <strong>Punjab plains.<\/strong><\/li>\n\n\n\n<li>The other branch moves up the <strong>Brahmaputra valley<\/strong> in the north and northeast, resulting in widespread rainfall.\n<ul class=\"wp-block-list\">\n<li>A sub-branch impacts the <strong>Garo and Khasi Hills of Meghalaya.<\/strong><\/li>\n\n\n\n<li><strong>Mawsynram<\/strong>, situated on the crest of the Khasi Hills, records the highest average annual rainfall in the world.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-background has-fixed-layout\" style=\"background-color:#ebecf0\"><tbody><tr><td><strong>Note:<\/strong> It is essential to understand why the <strong>Tamil Nadu coast<\/strong> remains dry during this season. Two factors are responsible:<br><br>&#8211; <strong>The Tamil Nadu coast is parallel to the Bay of Bengal branch<\/strong> of the SouthWest monsoon.<br>&#8211; <strong>It lies in the rainshadow area<\/strong> of the Arabian Sea branch of the Southwest Monsoon.<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"461\" height=\"563\" src=\"https:\/\/wp-images.nextias.com\/cdn-cgi\/image\/format=auto\/blog\/uploads\/2024\/07\/5-1.png\" alt=\"South West Monsoon\" class=\"wp-image-9830\" srcset=\"https:\/\/wp-images.nextias.com\/cdn-cgi\/image\/format=auto\/blog\/uploads\/2024\/07\/5-1.png 461w, https:\/\/wp-images.nextias.com\/cdn-cgi\/image\/format=auto\/blog\/uploads\/2024\/07\/5-1-211x258.png 211w, https:\/\/wp-images.nextias.com\/cdn-cgi\/image\/format=auto\/blog\/uploads\/2024\/07\/5-1-344x420.png 344w, https:\/\/wp-images.nextias.com\/cdn-cgi\/image\/format=auto\/blog\/uploads\/2024\/07\/5-1-150x183.png 150w\" sizes=\"auto, (max-width: 461px) 100vw, 461px\" \/><\/figure>\n\n\n\n<h2 class=\"wp-block-heading has-text-color has-link-color wp-elements-d0adc4bd9eb2e9b9b187dc32f0e06642\" style=\"color:#015aa7\"><span class=\"ez-toc-section\" id=\"Conclusion\"><\/span><strong>Conclusion<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>The South West Monsoon is a complex and critical climatic system that profoundly impacts the subcontinent&#8217;s environment and economy. The South West Monsoon, with its intricate wind patterns and significant rainfall, is crucial for replenishing water sources and supporting agriculture. The variability and intricacies of monsoon behaviour, influenced by various climatic theories and regional factors, underscore the importance of ongoing research and monitoring. As we continue to study and understand these patterns, we can better prepare for and adapt to the challenges of monsoon variability and its effects on the Indian subcontinent.<\/p>\n\n\n\n<h2 class=\"wp-block-heading has-text-color has-link-color wp-elements-12bb222037a9f2dcb49d558eedca0ac8\" style=\"color:#015aa7\"><span class=\"ez-toc-section\" id=\"Difference_between_South_West_Monsoon_and_North_East_Monsoon\"><\/span><strong>Difference between South West Monsoon and North East Monsoon<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-background has-fixed-layout\" style=\"background-color:#ebecf0\"><thead><tr><th><strong>Aspects<\/strong><\/th><th><strong>South-West Monsoon\u00a0<\/strong><\/th><th><strong>North-East Monsoon<\/strong><\/th><\/tr><\/thead><tbody><tr><td>Season<\/td><td>June to September<\/td><td>October to December<\/td><\/tr><tr><td>Wind Direction&nbsp;<\/td><td>Southwest to Northeast (SW -&gt; NE)<\/td><td>Northeast to Southwest (NE -&gt; SW)<\/td><\/tr><tr><td>Source of Moisture&nbsp;<\/td><td>Indian Ocean&nbsp;<\/td><td>Bay of Bengal<\/td><\/tr><tr><td>Regions Affected&nbsp;<\/td><td>Most of India&nbsp;<\/td><td>South Eastern Coast of India, esp. Andhra Pradesh and Tamil Nadu<\/td><\/tr><tr><td>Type of Rainfall&nbsp;<\/td><td>Heavy Rainfall&nbsp;<\/td><td>Moderate Rainfall<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h2 class=\"wp-block-heading has-text-color has-link-color wp-elements-618812723183593a2c916a1fd5800128\" style=\"color:#015aa7\"><span class=\"ez-toc-section\" id=\"Frequently_Asked_Questions_FAQs\"><\/span><strong>Frequently Asked Questions (FAQs)<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n<div id=\"rank-math-faq\" class=\"rank-math-block\">\n<div class=\"rank-math-list \">\n<div id=\"faq-question-1722336186202\" class=\"rank-math-list-item\">\n<h3 class=\"rank-math-question \"><span class=\"ez-toc-section\" id=\"What_is_the_South_West_Monsoon\"><\/span><strong>What is the South West Monsoon?<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h3>\n<div class=\"rank-math-answer \">\n\n<p>The South West Monsoon is a seasonal wind pattern that brings heavy rainfall to the Indian subcontinent, typically from June to September. It occurs due to the differential heating of land and sea, where the Indian landmass heats up more than the surrounding ocean, causing moist air from the Indian Ocean to flow towards the land.<\/p>\n\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n\n\n<p><\/p>\n","protected":false},"excerpt":{"rendered":"<p>The SouthWest Monsoon in India is a major seasonal wind system that brings substantial rainfall to the Indian subcontinent from June to September. Its significance lies in its critical role in replenishing water resources and supporting agriculture across the region. This article aims to study in detail the characteristics, impacts, and mechanisms of the Southwest [&hellip;]<\/p>\n","protected":false},"author":9,"featured_media":9834,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[832,67],"tags":[73],"class_list":["post-9814","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-indian-geography","category-geography","tag-gs-1"],"_links":{"self":[{"href":"https:\/\/www.nextias.com\/blog\/wp-json\/wp\/v2\/posts\/9814","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.nextias.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.nextias.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.nextias.com\/blog\/wp-json\/wp\/v2\/users\/9"}],"replies":[{"embeddable":true,"href":"https:\/\/www.nextias.com\/blog\/wp-json\/wp\/v2\/comments?post=9814"}],"version-history":[{"count":7,"href":"https:\/\/www.nextias.com\/blog\/wp-json\/wp\/v2\/posts\/9814\/revisions"}],"predecessor-version":[{"id":9841,"href":"https:\/\/www.nextias.com\/blog\/wp-json\/wp\/v2\/posts\/9814\/revisions\/9841"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.nextias.com\/blog\/wp-json\/wp\/v2\/media\/9834"}],"wp:attachment":[{"href":"https:\/\/www.nextias.com\/blog\/wp-json\/wp\/v2\/media?parent=9814"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.nextias.com\/blog\/wp-json\/wp\/v2\/categories?post=9814"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.nextias.com\/blog\/wp-json\/wp\/v2\/tags?post=9814"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}