[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"detail-sidebar-cat-0-en-105":3,"doc-seo-388485-105":59,"doc-detail-388485-en":130},{"code":4,"msg":5,"data":6},0,"success",[7,13,18,23,28,33,38,43,48,51,55],{"id":8,"doc_module":4,"doc_module_name":9,"category_name":10,"show_sort_weight":11,"slug":12},1,"Document","Story & Novel",90,"story-novel",{"id":14,"doc_module":4,"doc_module_name":9,"category_name":15,"show_sort_weight":16,"slug":17},2,"Literature",80,"literature",{"id":19,"doc_module":4,"doc_module_name":9,"category_name":20,"show_sort_weight":21,"slug":22},4,"Exam",70,"exam",{"id":24,"doc_module":4,"doc_module_name":9,"category_name":25,"show_sort_weight":26,"slug":27},5,"Comic",60,"comic",{"id":29,"doc_module":4,"doc_module_name":9,"category_name":30,"show_sort_weight":31,"slug":32},6,"Technology",50,"technology",{"id":34,"doc_module":4,"doc_module_name":9,"category_name":35,"show_sort_weight":36,"slug":37},7,"Healthcare",40,"healthcare",{"id":39,"doc_module":4,"doc_module_name":9,"category_name":40,"show_sort_weight":41,"slug":42},8,"Research & Report",30,"research-report",{"id":44,"doc_module":4,"doc_module_name":9,"category_name":45,"show_sort_weight":46,"slug":47},9,"Religion & Spirituality",20,"religion-spirituality",{"id":46,"doc_module":4,"doc_module_name":9,"category_name":49,"show_sort_weight":46,"slug":50},"World Cup","world-cup",{"id":52,"doc_module":4,"doc_module_name":9,"category_name":53,"show_sort_weight":52,"slug":54},10,"Lifestyle","lifestyle",{"id":56,"doc_module":4,"doc_module_name":9,"category_name":57,"show_sort_weight":24,"slug":58},19,"General","general",{"code":4,"msg":60,"data":61},"ok",{"site_id":62,"language":63,"slug":64,"title":65,"keywords":66,"description":67,"schema_data":68,"social_meta":123,"head_meta":125,"extra_data":127,"updated_unix":129},105,"en","tc-formation-and-rainfall-outlook-august-20th-update","TC Formation and Rainfall Outlook - August 20th Update","","Tropical cyclone (TC) hazard outlook updates focus on evolving intraseasonal tropical dynamics, including forecasts for a Kelvin wave crossing the Indian Ocean toward the Maritime Continent in 10–15 days. Monitoring by NHC and JTWC describes shifting formation probabilities for disturbances in the Atlantic, East Pacific, Central Pacific, and West Pacific, with several systems introduced or removed based on guidance. Wind shear and subsidence trends over the Atlantic MDR inform Week-2 cyclogenesis risk, while rainfall anomalies are revised using latest TC track and precipitation model forecasts.",{"@graph":69,"@context":122},[70,84,105],{"@type":71,"itemListElement":72},"BreadcrumbList",[73,77,79,82],{"item":74,"name":75,"@type":76,"position":8},"https://docshare.wps.com","Home","ListItem",{"item":78,"name":9,"@type":76,"position":14},"https://docshare.wps.com/document/",{"item":80,"name":35,"@type":76,"position":81},"https://docshare.wps.com/document/healthcare/",3,{"item":83,"name":65,"@type":76,"position":19},"https://docshare.wps.com/document/tc-formation-and-rainfall-outlook-august-20th-update/388485/",{"url":83,"name":65,"@type":85,"image":86,"author":91,"headline":65,"publisher":94,"fileFormat":97,"inLanguage":63,"description":67,"dateModified":98,"datePublished":99,"encodingFormat":97,"isAccessibleForFree":100,"interactionStatistic":101},"DigitalDocument",{"url":87,"@type":88,"width":89,"height":90},"https://docshare.wps.com/thumbnails/tc-formation-and-rainfall-outlook-august-20th-update/388485.png","ImageObject",300,407,{"name":92,"@type":93},"Sophia Brooks","Person",{"url":74,"name":95,"@type":96},"DocShare","Organization","application/pdf","2026-10-29","2026-09-25",true,{"@type":102,"interactionType":103,"userInteractionCount":39},"InteractionCounter",{"@type":104},"ViewAction",{"@type":106,"mainEntity":107},"FAQPage",[108,114,118],{"name":109,"@type":110,"acceptedAnswer":111},"What tropical wave feature is highlighted as central to the next 10–15 days?","Question",{"text":112,"@type":113},"A Kelvin wave is forecast to track rapidly across the Indian Ocean toward the Maritime Continent, influencing broader intraseasonal conditions.","Answer",{"name":115,"@type":110,"acceptedAnswer":116},"How do NHC and JTWC assessments affect TC formation odds in this outlook?",{"text":117,"@type":113},"They provide formation probabilities for specific disturbances, and guidance is used to add or drop hazard areas when odds change between 48 hours and 5 days (and 24 hours for JTWC monitoring).",{"name":119,"@type":110,"acceptedAnswer":120},"Why is the Atlantic Week-2 cyclogenesis risk tied to wind shear and subsidence?",{"text":121,"@type":113},"Even with relaxed wind shear after the Kelvin wave passage, broad subsidence over the main development region remains a limiting factor, shaping where and whether a TC formation focus is maintained.","https://schema.org",{"og:url":83,"og:type":124,"og:title":65,"og:site_name":95,"og:description":67},"article",{"robots":126,"canonical":83},"index,follow",{"doc_id":128,"site_id":62},388485,1790997174,{"code":4,"msg":5,"data":131},{"doc_id":128,"user_id":132,"nickname":92,"user_avatar":133,"doc_module":4,"category_id":34,"category_name":35,"doc_title":65,"doc_description":67,"doc_content":134,"file_id":135,"file_url":136,"file_type":137,"file_size":138,"view_count":39,"is_deleted":4,"is_public":8,"is_downloadable":8,"audit_status":8,"page_count":81,"language":139,"language_code":63,"site_id":62,"html_lang":63,"table_of_contents":140,"faqs":141,"seo_title":142,"seo_description":67,"update_tm":143,"read_time":39,"preview_page_count":4},962084925636,"https://ap-avatar.wpscdn.com/davatar_994ba38a5ba835b3df7d355c54d3ed8d","The original outlook remains largely on track, with dynamical model forecasts converging around the earlier GEFS/CFS perspective regarding a Kelvin wave tracking rapidly across the Indian Ocean to the Maritime Continent over the next 10-15 days. There is some projection of this feature onto the RMM Index, although the phase speed of the eastward propagating intraseasonal envelope is near the boundary of characteristic MJO and Kelvin wave events (period of approximately 20-25 days) .  \nNHC is currently monitoring a disturbance over the Bahamas, giving it a 70%(90%) chance of becoming a TC over the next 48 hours (5 days) off the Southeast coast, resulting in a high risk for TC formation being introduced here. NHC is also monitoring a tropical wave near 10N/43W, with 40%(50%) chances of development over the next 48 hours (5 days), which corresponds to moderate confidence of TC formation in this outlook. In the East Pacific, Tropical Storm Ivo formed on the 21st, verifying the high risk from the original outlook that is subsequently dropped from this update. The moderate risk of TC formation area from the original outlook may have missed its chance to develop, as the Central Pacific Hurricane Center now gives it a near 0 (30%) chance of forming over the next 48 hrs (5 days), resulting init being left off the update. Tropical Storm Bailu formed over the West Pacific on the 21st and is forecast to track across Taiwan over the weekend. JTWC is monitoring another system (99W) near 7N/145E that  \nhas a low chance of developing in the next 24 hours, but dynamical model guidance is more supportive of development over the weekend or early next week, resulting in a moderate confidence of TC formation area being included east of the Philippines.  \nAs anticipated, wind shear over the Atlantic main development region (MDR) has relaxed in the wake of the Kelvin wave passage. Broad subsidence continues to be forecast over the MDR consistent with the low-frequency state. Model guidance is more bullish than Tuesday on possible TC formation in the vicinity of Cape Verde during Week-2, resulting in moderate confidence of cyclogenesis for a region roughly between 10-20N and 50W and the African coastline. The west-southwest to east-northeast orientation of the TC formation focus suggests a relatively southern track for the system around the base of the subtropical high, supporting a potential track toward the Lesser Antilles during the first third of September. U.S. interests should also pay close attention to subsequent updates of this outlook for more information as the system possibly comes closer to becoming a reality. The Week-2 West Pacific TC formation area is maintained, while any activity southeast of Hawaii appears less likely resulting in that area being downgraded from the graphic.  \nAbove-and below-normal precipitation regions from Tuesday are updated to reflect the latest guidance regarding TC tracks in addition to dynamical model precipitation forecasts.  \n-----The original discussion from Tuesday, August 20th follows below. -----  \nThe Madden-Julian Oscillation (MJO) remained incoherent over the past week, while higher frequency modes of variability such as Kelvin and equatorial Rossby waves dominated the tropics. The most prominent of these features appears to be a Kelvin wave that is most recently analyzed near South America, with origins from extratropical wavebreaking over the Southern Hemisphere. Model guidance varies in whether this feature is able to grow and slow down into a full-fledged MJO (ECMWF) or remains transient (CFS and GEFS) . This Kelvin wave feature is likely to help relax environmental windshear across the main development region in the Atlantic for tropical cyclones (TCs), although model guidance continues to project broad subsidence across the basin. While this combination is slightly more supportive for any easterly waves exiting Africa to become TCs, the large-scale subsidence remains a significant limiter for","cbCaidlKaiz0lN3P","https://ap.wps.com/l/cbCaidlKaiz0lN3P","pdf",331003,"English","# Tropical dynamics and precipitation drivers\n## Kelvin wave and MJO coherence\n# Atlantic basin TC formation risk\n## Wind shear relaxation and subsidence\n# Pacific basin monitoring and TC development\n## East/Central Pacific disturbances and JTWC signals\n# West Pacific and ongoing systems\n## Taiwan track and additional monitoring\n# Rainfall anomaly updates\n## Above-/below-normal precipitation guidance","[{\"question\":\"What tropical wave feature is highlighted as central to the next 10–15 days?\",\"answer\":\"A Kelvin wave is forecast to track rapidly across the Indian Ocean toward the Maritime Continent, influencing broader intraseasonal conditions.\"},{\"question\":\"How do NHC and JTWC assessments affect TC formation odds in this outlook?\",\"answer\":\"They provide formation probabilities for specific disturbances, and guidance is used to add or drop hazard areas when odds change between 48 hours and 5 days (and 24 hours for JTWC monitoring).\"},{\"question\":\"Why is the Atlantic Week-2 cyclogenesis risk tied to wind shear and subsidence?\",\"answer\":\"Even with relaxed wind shear after the Kelvin wave passage, broad subsidence over the main development region remains a limiting factor, shaping where and whether a TC formation focus is maintained.\"}]","TC Formation and Rainfall Outlook - August 20th Update | PDF",1790304669]