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A radar-based nowcasting scheme is developed to predict lightning initiation and intensity. The approach builds on a four-stage lightning evolution sequence using selected radar predictors and emphasizes near-storm thermal structure through derivation of isothermal radar reflectivities. Preliminary testing results and future improvement directions are discussed.",{"@graph":69,"@context":123},[70,84,106],{"@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":40,"@type":76,"position":81},"https://docshare.wps.com/document/research-report/",3,{"item":83,"name":65,"@type":76,"position":19},"https://docshare.wps.com/document/lightning-initiation-and-intensity-nowcasting-based-on-isothermal-radar-reflectivity-a-conceptual-model/238677/",{"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/lightning-initiation-and-intensity-nowcasting-based-on-isothermal-radar-reflectivity-a-conceptual-model/238677.png","ImageObject",300,407,{"name":92,"@type":93},"Lucas Vance","Person",{"url":74,"name":95,"@type":96},"DocShare","Organization","application/pdf","2026-10-28","2026-09-11",true,{"@type":102,"interactionType":103,"userInteractionCount":105},"InteractionCounter",{"@type":104},"ViewAction",11,{"@type":107,"mainEntity":108},"FAQPage",[109,115,119],{"name":110,"@type":111,"acceptedAnswer":112},"What problem does the paper address?","Question",{"text":113,"@type":114},"The paper addresses radar-based nowcasting of lightning initiation and lightning intensity for severe convective storms in Hong Kong.","Answer",{"name":116,"@type":111,"acceptedAnswer":117},"How is the lightning initiation process modeled?",{"text":118,"@type":114},"The scheme assumes a four-stage evolution sequence within the thunderstorm lifecycle, as summarized in a conceptual model table.",{"name":120,"@type":111,"acceptedAnswer":121},"Why are isothermal radar reflectivities important?",{"text":122,"@type":114},"Isothermal radar reflectivities link lightning-relevant charge development to near-storm thermal structure rather than using height alone.","https://schema.org",{"og:url":83,"og:type":125,"og:title":65,"og:site_name":95,"og:description":67},"article",{"robots":127,"canonical":83},"index,follow",{"doc_id":129,"site_id":62},238677,1789138814,{"code":4,"msg":5,"data":132},{"doc_id":129,"user_id":133,"nickname":92,"user_avatar":134,"doc_module":4,"category_id":39,"category_name":40,"doc_title":65,"doc_description":67,"doc_content":135,"file_id":136,"file_url":137,"file_type":138,"file_size":139,"view_count":105,"is_deleted":4,"is_public":8,"is_downloadable":8,"audit_status":8,"page_count":29,"language":140,"language_code":63,"site_id":62,"html_lang":63,"table_of_contents":141,"faqs":142,"seo_title":143,"seo_description":67,"update_tm":130,"read_time":144,"preview_page_count":4},549768064622,"https://ap-avatar.wpscdn.com/davatar_6f874abed73319feea01a86fa6f0fab8","11A.7 LIGHTNING INITIATION AND INTENSITY NOWCASTING BASED ON ISOTHERMAL RADAR REFLECTIVITY — A CONCEPTUAL MODEL  \nLinus H.Y. Yeung * 1, Edwin S.T. Lai 1 and Samson K. S. Chiu2  \n1 Hong Kong Observatory, Hong Kong, China  \n2 City University of Hong Kong, Hong Kong, China  \n1. INTRODUCTION  \nIntense convective activity associated with summer monsoon, monsoon troughs and tropical cyclones poses a major weather threat in the warm seasons of Hong Kong. Very often, such intense convective activity will also trigger other types of hazardous weathers . As shown in Table I, lightning strikes, heavy rainstorms, damaging downbursts/squalls, hails, waterspouts and even tornadoes are not uncommon in Hong Kong. In terms of occurrence frequencies as shown in Table I, thunderstorm lightning is actually the most frequent type of weather hazard in Hong Kong. At the Hong Kong Observatory (HKO), a second generation nowcasting system is currently under development to track and nowcast such severe weather phenomena . For more details on SWIRLS (Short-range Warning of Intense Rainstorms in Localized Systems ), readers are referred to Li and Lai 2004.  \nIn this paper, a radar-based scheme for the nowcasting of lightning initiation and intensity is presented. In Section 2, the simple conceptual model behind the scheme is outlined. The selection of key radar parameters as lightning predictors and the considerations involved are given in Section 3. The importance of near-storm thermal structure and the corresponding derivation of isothermal radar reflectivities are highlighted in Section 4. The details of the lightning nowcast scheme are documented in Section 5 and the preliminary testing results presented in Section 6. Conclusionsand further improvement areas are discussed in Section 7.  \n2. CONCEPTUAL MODEL  \nFollowing Zajac and Weaver’s extension (Zajac & Weaver 2002) to the classical thunderstorm lifecycle of Byers and Braham (1949), we assume a lightning initiation process through the 4-stage evolution sequence as shown in Table II.  \nSymbols ⇑ and ⇓ in Table II represent updraft and downdraft in a convective cloud, whereas ←→ and →←  \n* Corresponding author address: Linus H.Y. Yeung, Hong Kong Observatory, 134A, Nathan Road, Kowloon, Hong Kong, China; e-mail: [hyyeung@hko.gov.hk](hyyeung@hko.gov.hk)  \nTable I – Occurrence frequencies of various types of weather hazards in the warm seasons of Hong Kong.  \n\n| Weather Hazards | Period | Total Number |\n| --- | --- | --- |\n| Thunder/Lighting | 1977-2006 | 2620 warnings |\n| Amber Rainstorm(1) | 1997-2006 | 240 warnings |\n| Red Rainstorm(1) | 1997-2006 | 48 warnings |\n| Black Rainstorm(1) | 1997-2006 | 13 warnings |\n| Severe Squalls(2) | 1987-2006 | 214 days |\n| Hail | 1977-2006 | 30 reports |\n| Waterspout | 1977-2006 | 22 reports |\n| Tornado | 1982-2006 | 8 reports |\n\nNote: (1) Amber, Red and Black Rainstorms respectively refer to hourly rainfall ≥ 30, 50 and 70 mm widespread over Hong Kong. (2) Severe squalls is operationally defined as 1-sec wind speed ≥ 70 km/h (near surface) .  \nimply divergence and convergence respectively. Hydrometeors critical to cumulus cloud electrification, namely cloud liquid water, supercooled cloud liquid water, ice crystal and graupel, are denoted by symbols \",\", *, and 􀀑 respectively. Positive and negative charges are presented by symbols r and s . Positive and negative ground strikes are symbolized as 􀀀 and 􀀀 . The symbol 􀀏 has its usual meaning of shower. The relative sizes of these symbols are drawn to contrast their relative abundance/magnitude.  \nThough simplistic, the conceptual model in Table II captures the essence of recent studies on cloud electrification, namely: (i) the formation of graupel at sub-zero levels and its correlation to initial electrification (Dye et al 1986); (ii) charges generated by graupel-ice collision under strong convection; (iii) charges separated vertically by updrafts and downdrafts resulting in a large-scale electrical dipole structure ","cbCaigcvhYHaP7up","https://ap.wps.com/l/cbCaigcvhYHaP7up","pdf",1984447,"English","# Introduction\n## Conceptual model","[{\"question\":\"What problem does the paper address?\",\"answer\":\"The paper addresses radar-based nowcasting of lightning initiation and lightning intensity for severe convective storms in Hong Kong.\"},{\"question\":\"How is the lightning initiation process modeled?\",\"answer\":\"The scheme assumes a four-stage evolution sequence within the thunderstorm lifecycle, as summarized in a conceptual model table.\"},{\"question\":\"Why are isothermal radar reflectivities important?\",\"answer\":\"Isothermal radar reflectivities link lightning-relevant charge development to near-storm thermal structure rather than using height alone.\"}]","Lightning Initiation and Intensity Nowcasting Based on Isothermal Radar Reflectivity - A Conceptual Model | PDF",15]