DOCSLIB.ORG

The Genesis of Typhoon Nuri As Observed During the Tropical Cyclone Structure 2008 (TCS-08) field Experiment – Part 1: the Role of the Easterly Wave Critical Layer

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The Genesis of Typhoon Nuri As Observed During the Tropical Cyclone Structure 2008 (TCS-08) field Experiment – Part 1: the Role of the Easterly Wave Critical Layer Atmos. Chem. Phys., 10, 9879–9900, 2010 www.atmos-chem-phys.net/10/9879/2010/ Atmospheric doi:10.5194/acp-10-9879-2010 Chemistry © Author(s) 2010. CC Attribution 3.0 License. and Physics The genesis of Typhoon Nuri as observed during the Tropical Cyclone Structure 2008 (TCS-08) field experiment – Part 1: The role of the easterly wave critical layer M. T. Montgomery, L. L. Lussier III, R. W. Moore, and Z. Wang Naval Postgraduate School, Monterey, California, USA Received: 5 June 2009 – Published in Atmos. Chem. Phys. Discuss.: 16 September 2009 Revised: 14 April 2010 – Accepted: 25 May 2010 – Published: 20 October 2010 Abstract. An observational and real-time model forecast Real-time forecasts were produced using operational study of the genesis of Typhoon Nuri during the Tropical Cy- global prediction model data to support scientific missions clone Structure 2008 (TCS-08) field campaign in the western during TCS-08. These forecasts were found to be useful North Pacific sector is presented. Analysis and observational in flight planning discussions and predicted Typhoon Nuri’s data show that the surrounding base state is an easterly trade eventual genesis latitude within 1.5 degrees 72 h in advance. wind flow and the precursor disturbance to Typhoon Nuri is an easterly wave that originates in the ITCZ in the Central Pa- cific. This disturbance can be tracked more than 10 days prior to tropical storm formation. An overview of the field data is 1 Introduction presented here using a newly proposed dynamical framework The western North Pacific region is the most active trop- for tropical cyclone formation within the critical layer of an ical cyclone (TC) basin on the earth, responsible for, on easterly wave. Despite propagating through a hostile envi- average, 26 of the 84 named storms annually (Neumann, ronment ripe with strong vertical wind shear and relatively 1993). Numerous synoptic-scale patterns have been iden- dry air, the easterly wave critical layer protects the proto- tified as favorable to tropical cyclogenesis over the years, vortex and allows it to gestate until it reaches a more favor- including, but not limited to: Tropical Upper Tropospheric able environment. Within this protective “Kelvin cat’s eye Troughs (TUTT) (e.g., Sadler, 1976, 1978), formation within flow” located within the wave’s critical layer existed a sweet a monsoon trough regime (e.g., Holland, 1995) including spot, defined as the intersection between the wave trough and the special cases of monsoon depression formation (Harr critical latitude, which is the preferred location for tropical et al., 1996) and monsoon gyre formation (Lander, 1994), cyclogenesis. Global Forecast System Final Analyses and wave energy dispersion from pre-existing depressions (Carr IR satellite imagery, which shows convective bands wrap- and Elsberry, 1995; Holland, 1995), filamentary intrusions ping around the sweet spot as genesis nears, confirm that this from the subtropics (Deleon, 2008), mixed Rossby-gravity sweet spot is the location where Typhoon Nuri’s dominant waves (Dickinson and Molinari, 2002), and easterly waves low-level circulation emerges. (Ritchie and Holland, 1999; Fu et al., 2007). Ritchie and United States Air Force C130 and Naval Research Labora- Holland (1999) present a climatology of formation mecha- tory P3 research flights on 16 and 17 August collected flight- nisms in this basin and document five synoptic-scale regimes level, dropwindsonde, and Doppler radar data that allowed favorable to tropical cyclogenesis1. Using eight years data an evaluation of the dynamic and thermodynamic processes from the Australian Bureau of Meteorology tropical anal- within the cat’s eye circulation. The dropwindsonde analy- ysis scheme, they attribute 42% of the western North Pa- ses identifies the precursor easterly wave disturbance on 16 cific tropical cyclogenesis cases to monsoon shear lines, 29% August and identifies an area of weak low-level cyclonic cir- to monsoon confluent regions, 18% to easterly wave distur- culation on 17 August. bances, 8% to wave energy dispersion, and 3% to monsoon gyre formations. Ritchie and Holland (1999) note that these 1Ritchie and Holland (1999) define genesis as: “... the series of Correspondence to: M. T. Montgomery physical processes by which a warm-core, tropical cyclone–scale ([email protected]) vortex with maximum amplitude near the surface forms”. Published by Copernicus Publications on behalf of the European Geosciences Union. 9880 M. T. Montgomery et al.: The role of the easterly wave critical layer data most likely underestimate the true number of easterly Using the National Hurricane Center best track data, Na- wave type formations: “development may also occur entirely tional Aeronautics and Space Administration (NASA) Trop- in the easterly wave (18% of cases examined here) although ical Rainfall Measurement Mission (TRMM) data, and Eu- the sample for this pattern most probably has a low bias due ropean Center for Medium-range Weather Prediction Fore- to the exclusion of genesis cases near the date line”. Ad- casts (ECMWF) Reanalysis (ERA-40) data during August ditionally, they note: “It is difficult to distinguish between and September (1998–2001), they examined tropical cyclone genesis in the confluence region and genesis directly from formation from quasi-monochromatic easterly waves in the an easterly wave because of the uncertainty of when genesis Atlantic and eastern Pacific basins and proposed a dynamical processes have finished”. It is possible that the easterly wave pathway to genesis that held true in 53/55 cases4. pathway to genesis is more prominent in the western North This proposed tropical cyclogenesis sequence is centered Pacific basin than Ritchie and Holland (1999) suggest. Moli- around three new hypotheses (hereafter H1–H3) examining nari et al. (2004) examine genesis cases in the western North the flow dynamics, moist thermodynamics, and wave/vortex Pacific basin and “...believe that a significant fraction, and interactions associated with the Kelvin cat’s eye flow within likely the majority, of western-Pacific tropical cyclones form the critical layer of a tropical easterly wave. The cat’s eye in association with westward moving disturbances”. Chen et flow is hypothesized to be important to tropical storm for- al. (2008), for example, have proposed that 80% of the tropi- mation because: H1) wave breaking or roll-up of the cy- cal cyclone formations in this basin are due to easterly wave2 clonic vorticity near the critical surface in the lower tropo- influences either directly or indirectly (through wave-gyre in- sphere provides a favorable environment for the aggregation teractions)3. of vorticity seedlings for TC formation; H2) the cat’s eye Although easterly waves are ubiquitous in the trade wind is a region of approximately closed Lagrangian circulation, region of the tropics, typically only a small percentage of and air is repeatedly moistened by convection and protected these waves develop into tropical cyclones (Frank, 1970; to some degree from dry air intrusion, which favors a pre- Ritchie and Holland, 1999). Recently, Dunkerton, Mont- dominantly convective type of heating profile; and H3) the gomery, and Wang (2009; hereafter DMW09) have devel- parent wave is maintained and possibly enhanced by diabat- oped a new framework to describe the transition sequence ically amplified mesoscale vortices within the cat’s eye. The from synoptic-scale easterly wave to tropical depression. cat’s eye circulation has been shown to be the favored region of storm formation, with the eventual storm center located 2In their analysis, Chen et al. (2008) did not distinguish be- near the intersection of the wave’s critical surface and trough tween easterly waves and other westward propagating wave distur- axis (i.e., the “sweet spot”). This cyclogenesis sequence is bances such as mixed Rossby-gravity and equatorial Rossby waves likened by DMW09 to the development of a marsupial infant that have been shown to lead to tropical cyclogenesis in the west- in its mother’s pouch5 wherein the juvenile proto-vortex is ern North Pacific (e.g., Dickinson and Molinari, 2002; Frank and Roundy, 2006). This reference nonetheless serves to illustrate that 4The two remaining storms were found also to develop in a re- there is a school of thought that believes wave activity is more gion of closed circulation when the meridional component of wave prominent in western North Pacific tropical cyclone formation (e.g., propagation is accounted for, although in one of these cases, the Molinari et al., 2004) than many researchers are willing to believe. horizontal resolution of ERA-40 is barely adequate. For a complete While we care deeply about the different types of waves, the ques- definition of all technical terms used herein please consult DMW09 tions of how they lead to tropical cyclogenesis, and whether or not and the Glossary therein. they can be analyzed in the marsupial framework must await future 5The term “pouch” is defined in DMW09 as the flow bounded by study. Nuri represents a useful and illustrative easterly wave case the closed streamline that passes through the stagnation point clos- that represents a first step in a long process to explore the utility est to the sweet spot. The region of recirculating quasi-horizontal of the marsupial paradigm in this basin. Finally, we note that re- flow located within is the so-called Kelvin cat’s eye circulation. search is underway to study different types of western North Pacific Certain characteristics of the pouch, specifically the moisture gradi- waves and how the marsupial paradigm could be applied to these ent, are used here and elsewhere (Wang et al., 2009) to identify the cases. A particularly interesting case involves Super Typhoon Man- horizontal extent and location of the pouch. yi (2007), whose precursor disturbance was an equatorial Rossby Although the Kelvin cat’s eye now serves as a canonical illus- wave and to which some of the marsupial ideas seem applicable tration of ‘anti-mixing’ behavior in the two-dimensional fluid dy- (Lussier, 2010).
Load more

Recommended publications
  • Recent Advances in Research on Tropical Cyclogenesis
    Available online at www.sciencedirect.com ScienceDirect Tropical Cyclone Research and Review 9 (2020) 87e105 www.keaipublishing.com/tcrr Recent advances in research on tropical cyclogenesis Brian H. Tang a,*, Juan Fang b, Alicia Bentley a,y, Gerard Kilroy c, Masuo Nakano d, Myung-Sook Park e, V.P.M. Rajasree f, Zhuo Wang g, Allison A. Wing h, Liguang Wu i a University at Albany, State University of New York, Albany, USA b Nanjing University, Nanjing, China c Ludwig-Maximilians University of Munich, Munich, Germany d Japan Agency for Marine-Earth Science and Technology, Yokohama, Japan e Korea Institute of Ocean Science and Technology, Busan, South Korea f Centre for Atmospheric and Climate Physics Research, University of Hertfordshire, Hatfield, UK g University of Illinois, Urbana, USA h Florida State University, Tallahassee, USA i Fudan University, Shanghai, China Available online 7 May 2020 Abstract This review article summarizes recent (2014e2019) advances in our understanding of tropical cyclogenesis, stemming from activities at the ninth International Workshop on Tropical Cyclones. Tropical cyclogenesis involves the interaction of dynamic and thermodynamic processes at multiple spatio-temporal scales. Studies have furthered our understanding of how tropical cyclogenesis may be affected by external processes, such as intraseasonal oscillations, monsoon circulations, the intertropical convergence zone, and midlatitude troughs and cutoff lows. Addi- tionally, studies have furthered our understanding of how tropical cyclogenesis may be affected by internal processes, such as the organization of deep convection; the evolution of the “pouch” structure; the role of friction; the development of the moist, warm core; the importance of surface fluxes; and the role of the mid-level vortex.
    [Show full text]
  • Report on UN ESCAP / WMO Typhoon Committee Members Disaster Management System
    Report on UN ESCAP / WMO Typhoon Committee Members Disaster Management System UNITED NATIONS Economic and Social Commission for Asia and the Pacific January 2009 Disaster Management ˆ ` 2009.1.29 4:39 PM ˘ ` 1 ¿ ‚fiˆ •´ lp125 1200DPI 133LPI Report on UN ESCAP/WMO Typhoon Committee Members Disaster Management System By National Institute for Disaster Prevention (NIDP) January 2009, 154 pages Author : Dr. Waonho Yi Dr. Tae Sung Cheong Mr. Kyeonghyeok Jin Ms. Genevieve C. Miller Disaster Management ˆ ` 2009.1.29 4:39 PM ˘ ` 2 ¿ ‚fiˆ •´ lp125 1200DPI 133LPI WMO/TD-No. 1476 World Meteorological Organization, 2009 ISBN 978-89-90564-89-4 93530 The right of publication in print, electronic and any other form and in any language is reserved by WMO. Short extracts from WMO publications may be reproduced without authorization, provided that the complete source is clearly indicated. Editorial correspon- dence and requests to publish, reproduce or translate this publication in part or in whole should be addressed to: Chairperson, Publications Board World Meteorological Organization (WMO) 7 bis, avenue de la Paix Tel.: +41 (0) 22 730 84 03 P.O. Box No. 2300 Fax: +41 (0) 22 730 80 40 CH-1211 Geneva 2, Switzerland E-mail: [email protected] NOTE The designations employed in WMO publications and the presentation of material in this publication do not imply the expression of any opinion whatsoever on the part of the Secretariat of WMO concerning the legal status of any country, territory, city or area, or of its authorities, or concerning the delimitation of its frontiers or boundaries.
    [Show full text]
  • Minnesota Weathertalk Newsletter for Friday, January 3, 2014
    Minnesota WeatherTalk Newsletter for Friday, January 3, 2014 To: MPR's Morning Edition From: Mark Seeley, Univ. of Minnesota, Dept of Soil, Water, and Climate Subject: Minnesota WeatherTalk Newsletter for Friday, January 3, 2014 HEADLINES -December 2013 was climate near historic for northern communities -Cold start to 2014 -Weekly Weather potpourri -MPR listener questions -Almanac for January 3rd -Past weather -Outlook Topic: December 2013 near historic for far north In assessing the climate for December 2013 it should be said that from the standpoint of cold temperatures the month was quite historic for many northern Minnesota communities, especially due to the Arctic cold that prevailed over the last few days of the month. Minnesota reported the coldest temperature in the 48 contiguous states thirteen times during the month, the highest frequency among all 48 states. Many northern observers saw overnight temperatures drop below -30 degrees F on several occasions. The mean monthly temperature for December from several communities ranked among the coldest Decembers ever. A sample listing includes: -4.1 F at International Falls, 2nd coldest all-time 4.6 F at Duluth, 8th coldest all-time 0.1 F at Crookston, 3rd coldest all-time -3.1 F at Roseau, 3rd coldest all-time 0.3 F at Park Rapids, 3rd coldest all-time -4.4 F at Embarrass, 2nd coldest all-time -4.1 F at Baudette, coldest all-time -3.7 F at Warroad, coldest all-time -2.9 F at Babbitt, coldest all-time -2.8 F at Gunflint Lake, coldest all-time In addition, some communities reported an exceptionally snowy month of December.
    [Show full text]
  • Statistical Characteristics of the Response of Sea Surface Temperatures to Westward Typhoons in the South China Sea
    remote sensing Article Statistical Characteristics of the Response of Sea Surface Temperatures to Westward Typhoons in the South China Sea Zhaoyue Ma 1, Yuanzhi Zhang 1,2,*, Renhao Wu 3 and Rong Na 4 1 School of Marine Science, Nanjing University of Information Science and Technology, Nanjing 210044, China; [email protected] 2 Institute of Asia-Pacific Studies, Faculty of Social Sciences, Chinese University of Hong Kong, Hong Kong 999777, China 3 School of Atmospheric Sciences, Sun Yat-Sen University and Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai 519082, China; [email protected] 4 College of Oceanic and Atmospheric Sciences, Ocean University of China, Qingdao 266100, China; [email protected] * Correspondence: [email protected]; Tel.: +86-1888-885-3470 Abstract: The strong interaction between a typhoon and ocean air is one of the most important forms of typhoon and sea air interaction. In this paper, the daily mean sea surface temperature (SST) data of Advanced Microwave Scanning Radiometer for Earth Observation System (EOS) (AMSR-E) are used to analyze the reduction in SST caused by 30 westward typhoons from 1998 to 2018. The findings reveal that 20 typhoons exerted obvious SST cooling areas. Moreover, 97.5% of the cooling locations appeared near and on the right side of the path, while only one appeared on the left side of the path. The decrease in SST generally lasted 6–7 days. Over time, the cooling center continued to diffuse, and the SST gradually rose. The slope of the recovery curve was concentrated between 0.1 and 0.5.
    [Show full text]
  • The Genesis of Typhoon Nuri As Observed During the Tropical Cyclone Structure 2008 (TCS-08) field Experiment – Part 1: the Role of the Easterly Wave Critical Layer
    Atmos. Chem. Phys. Discuss., 9, 19159–19203, 2009 Atmospheric www.atmos-chem-phys-discuss.net/9/19159/2009/ Chemistry © Author(s) 2009. This work is distributed under and Physics the Creative Commons Attribution 3.0 License. Discussions This discussion paper is/has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP if available. The genesis of Typhoon Nuri as observed during the Tropical Cyclone Structure 2008 (TCS-08) field experiment – Part 1: The role of the easterly wave critical layer M. T. Montgomery, L. L. Lussier III, R. W. Moore, and Z. Wang Naval Postgraduate School, Monterey, California, USA Received: 5 June 2009 – Accepted: 12 August 2009 – Published: 16 September 2009 Correspondence to: M. T. Montgomery ([email protected]) Published by Copernicus Publications on behalf of the European Geosciences Union. 19159 Abstract An observational and real-time model forecast study of the genesis of Typhoon Nuri during the Tropical Cyclone Structure 2008 (TCS-08) field campaign in the western North Pacific sector is presented. Analysis and observational data show that the sur- 5 rounding base state flow was an easterly trade wind flow and the precursor disturbance to Typhoon Nuri was an easterly wave that originated in the ITCZ in the Central Pacific and can be tracked more than 10 days prior to tropical storm formation. An overview of the field data is presented here using a newly proposed dynamical framework for tropical cyclone formation within the critical layer of an easterly wave. Despite propa- 10 gating through a hostile environment ripe with strong vertical wind shear and relatively dry air, the easterly wave critical layer protected the proto-vortex and allowed it to gestate until it reached a more favorable environment.
    [Show full text]
  • Intensification and Decay of Typhoon Nuri (2014) Associated with Cold Front and Southwesterly Airflow Observed in Satellite Cloud Images
    Journal of Marine Science and Technology, Vol. 25, No. 5, pp. 599-606 (2017) 599 DOI: 10.6119/JMST-017-0706-1 INTENSIFICATION AND DECAY OF TYPHOON NURI (2014) ASSOCIATED WITH COLD FRONT AND SOUTHWESTERLY AIRFLOW OBSERVED IN SATELLITE CLOUD IMAGES Kuan-Dih Yeh1, Ji-Chyun Liu1, Chee-Ming Eea1, Ching-Huei Lin1, Wen-Lung Lu1, Ching-Tsan Chiang1, Yung-Sheng Lee2, and Ada Hui-Chuan Chen3 Key words: super typhoons, satellite imagery, cold fronts. variety of weather patterns could be observed along the occluded fronts, with the possibility of thunderstorms and cloudy condi- tions accompanied by patchy rain or showers. ABSTRACT This paper presents a framework involving the use of remote sensing imagery and image processing techniques to analyze a I. INTRODUCTION 2014 super typhoon, Typhoon Nuri, and the cold occlusion that Investigating the effects of climate variability and global warm- occurred in the northwestern Pacific Ocean. The purpose of ing on the frequency, distribution, and variation of tropical storms this study was to predict the tracks and profiles of Typhoon (TSs) is valuable for disaster prevention (Gierach and Subrah- Nuri and the corresponding association with the induction of manyam, 2007; Acker et al., 2009). Cloud images provided by cold front occlusion. Three-dimensional typhoon profiles were satellite data can be used to analyze the cloud structures and dy- implemented to investigate the in-depth distribution of the cloud namics of typhoons (Wu, 2001; Pun et al., 2007; Pinẽros et al., top from surface cloud images. The results showed that cold fronts 2008, 2011; Liu et al., 2009; Zhang and Wang, 2009).
    [Show full text]
  • 2008 Tropical Cyclone Review Summarises Last Year’S Global Tropical Cyclone Activity and the Impact of the More Significant Cyclones After Landfall
    2008 Tropical Cyclone 09 Review TWO THOUSAND NINE Table of Contents EXECUTIVE SUMMARY 1 NORTH ATLANTIC BASIN 2 Verification of 2008 Atlantic Basin Tropical Cyclone Forecasts 3 Tropical Cyclones Making US Landfall in 2008 4 Significant North Atlantic Tropical Cyclones in 2008 5 Atlantic Basin Tropical Cyclone Forecasts for 2009 15 NORTHWEST PACIFIC 17 Verification of 2008 Northwest Pacific Basin Tropical Cyclone Forecasts 19 Significant Northwest Pacific Tropical Cyclones in 2008 20 Northwest Pacific Basin Tropical Cyclone Forecasts for 2009 24 NORTHEAST PACIFIC 25 Significant Northeast Pacific Tropical Cyclones in 2008 26 NORTH INDIAN OCEAN 28 Significant North Indian Tropical Cyclones in 2008 28 AUSTRALIAN BASIN 30 Australian Region Tropical Cyclone Forecasts for 2009/2010 31 Glossary of terms 32 FOR FURTHER DETAILS, PLEASE CONTACT [email protected], OR GO TO OUR CAT CENTRAL WEBSITE AT HTTP://WWW.GUYCARP.COM/PORTAL/EXTRANET/INSIGHTS/CATCENTRAL.HTML Tropical Cyclone Report 2008 Guy Carpenter ■ 1 Executive Summary The 2008 Tropical Cyclone Review summarises last year’s global tropical cyclone activity and the impact of the more significant cyclones after landfall. Tropical 1 cyclone activity is reviewed by oceanic basin, covering those that developed in the North Atlantic, Northwest Pacific, Northeast Pacific, North Indian Ocean and Australia. This report includes estimates of the economic and insured losses sus- tained from each cyclone (where possible). Predictions of tropical cyclone activity for the 2009 season are given per oceanic basin when permitted by available data. In the North Atlantic, 16 tropical storms formed during the 2008 season, compared to the 1950 to 2007 average of 9.7,1 an increase of 65 percent.
    [Show full text]
  • Remote Sensing Observations of the Subsidence Zone Within the Eye of Typhoon Nuri in Hong Kong in 2008 C.P
    Remote Sensing Observations of the Subsidence Zone Within the Eye of Typhoon Nuri in Hong Kong in 2008 C.P. Wong1, P.W. Chan1 1Hong Kong Observatory, 134A Nathan Road, Kowloon, Hong Kong, China, [email protected] ABSTR ACT to the south of Tsing Yi Island, and turned northwards There are a number of ground-based remote sensing to cross the northeastern part of Lantau Island, Tuen equipment operating at or near the Hong Kong Inter- Mun and Yuen Long that ev ening. Nuri then crossed national Airport (HKIA), including two wind prof ilers, a Deep Bay, the western part of Shenzhen and the Pearl minisodar (sonic radar) and a multi-wavelength micro- River Estuary that night and made a second landfall wav e radiometer. The wind profilers and minisodar near Nansha of the Guangdong province subse- are able to measure the three components of wind, quently . whilst the microwave radiometer provides the tem- Radar imagery in Figure 2 depicts that there was no perature profile of the troposphere continuously. In intense precipitation at 7 p.m. on 22 August 2008 at August 2008, during the period when Typhoon Nuri Siu Ho Wan and near the centre of Nuri. Only a f ew made landfall in Hong Kong, these equipment millimeters of rainfall were estimated in the imagery. prov ided continuous data f or close monitoring of the In f act, only a few millimeters of rainfall were recorded v ariation of dynamic and thermodynamic parameters by the automatic weather stations nearby Nuri’s eye. of the atmosphere. When the eye of Nuri approached HKIA, a subsidence zone with downward motion of up 2.
    [Show full text]
  • Impact of Storm Size on Prediction of Storm Track and Intensity Using the 2016 Operational GFDL Hurricane Model
    AUGUST 2017 B E N D E R E T A L . 1491 Impact of Storm Size on Prediction of Storm Track and Intensity Using the 2016 Operational GFDL Hurricane Model MORRIS A. BENDER Program in Atmospheric and Oceanic Sciences, Princeton University, Princeton, New Jersey TIMOTHY P. MARCHOK NOAA/GFDL, Princeton, New Jersey CHARLES R. SAMPSON Naval Research Laboratory, Monterey, California JOHN A. KNAFF NOAA/Center for Satellite Applications and Research, Fort Collins, Colorado MATTHEW J. MORIN Engility Holdings, Inc., Chantilly, Virginia (Manuscript received 20 December 2016, in final form 12 May 2017) ABSTRACT The impact of storm size on the forecast of tropical cyclone storm track and intensity is investigated using the 2016 version of the operational GFDL hurricane model. Evaluation was made for 1529 forecasts in the Atlantic, eastern Pacific, and western North Pacific basins, during the 2014 and 2015 seasons. The track and 2 intensity errors were computed from forecasts in which the 34-kt (where 1 kt 5 0.514 m s 1) wind radii ob- tained from the operational TC vitals that are used to initialize TCs in the GFDL model were replaced with wind radii estimates derived using an equally weighted average of six objective estimates. It was found that modifying the radius of 34-kt winds had a significant positive impact on the intensity forecasts in the 1–2 day lead times. For example, at 48 h, the intensity error was reduced 10%, 5%, and 4% in the Atlantic, eastern Pacific, and western North Pacific, respectively. The largest improvements in intensity forecasts were for those tropical cyclones undergoing rapid intensification, with a maximum error reduction in the 1–2 day forecast lead time of 14% and 17% in the eastern and western North Pacific, respectively.
    [Show full text]
  • 二零一七熱帶氣旋tropical Cyclones in 2017
    => TALIM TRACKS OF TROPICAL CYCLONES IN 2017 <SEP (), ! " Daily Positions at 00 UTC(08 HKT), :; SANVU the number in the symbol represents <SEP the date of the month *+ Intermediate 6-hourly Positions ,')% Super Typhoon NORU ')% *+ Severe Typhoon JUL ]^ BANYAN LAN AUG )% Typhoon OCT '(%& Severe Tropical Storm NALGAE AUG %& Tropical Storm NANMADOL JUL #$ Tropical Depression Z SAOLA( 1722) OCT KULAP JUL HAITANG JUL NORU( 1705) JUL NESAT JUL MERBOK Hong Kong / JUN PAKHAR @Q NALGAE(1711) ,- AUG ? GUCHOL AUG KULAP( 1706) HATO ROKE MAWAR <SEP JUL AUG JUL <SEP T.D. <SEP @Q GUCHOL( 1717) <SEP T.D. ,- MUIFA TALAS \ OCT ? HATO( 1713) APR JUL HAITANG( 1710) :; KHANUN MAWAR( 1716) AUG a JUL ROKE( 1707) SANVU( 1715) XZ[ OCT HAIKUI AUG JUL NANMADOL AUG NOV (1703) DOKSURI JUL <SEP T.D. *+ <SEP BANYAN( 1712) TALAS(1704) \ SONCA( 1708) JUL KHANUN( 1720) AUG SONCA JUL MERBOK (1702) => OCT JUL JUN TALIM( 1718) / <SEP T.D. PAKHAR( 1714) OCT XZ[ AUG NESAT( 1709) T.D. DOKSURI( 1719) a JUL APR <SEP _` HAIKUI( 1724) DAMREY NOV NOV de bc KAI-( TAK 1726) MUIFA (1701) KIROGI DEC APR NOV _` DAMREY( 1723) OCT T.D. APR bc T.D. KIROGI( 1725) T.D. T.D. JAN , ]^ NOV Z , NOV JAN TEMBIN( 1727) LAN( 1721) TEMBIN SAOLA( 1722) DEC OCT DEC OCT T.D. OCT de KAI- TAK DEC 更新記錄 Update Record 更新日期: 二零二零年一月 Revision Date: January 2020 頁 3 目錄 更新 頁 189 表 4.10: 二零一七年熱帶氣旋在香港所造成的損失 更新 頁 217 附件一: 超強颱風天鴿(1713)引致香港直接經濟損失的 新增 估算 Page 4 CONTENTS Update Page 189 TABLE 4.10: DAMAGE CAUSED BY TROPICAL CYCLONES IN Update HONG KONG IN 2017 Page 219 Annex 1: Estimated Direct Economic Losses in Hong Kong Add caused by Super Typhoon Hato (1713) 二零一 七 年 熱帶氣旋 TROPICAL CYCLONES IN 2017 2 二零一九年二月出版 Published February 2019 香港天文台編製 香港九龍彌敦道134A Prepared by: Hong Kong Observatory 134A Nathan Road Kowloon, Hong Kong © 版權所有。未經香港天文台台長同意，不得翻印本刊物任何部分內容。 ©Copyright reserved.
    [Show full text]
  • The MJO Continues to Be Weak According to Both the RMM And
    The MJO continues to be weak according to both the RMM and CPC indices, though there is some suggestion that a weak enhanced phase may be emerging over the Western Hemisphere. The pattern continues to be complicated by westward-moving variability, including tropical cyclones, over the western Pacific, Maritime Continent, and Indian Ocean. As the ongoing TC activity over the Bay of Bengal times off, and with Nuri’s departure to the north, the velocity potential structure is expected to evolve toward a more coherent wave-1 structure over the eastern Pacific and Americas over the next several days, in phase with the weak low-frequency state. This is expected to propagate quickly into the western Indian Ocean during Week-2. The updates made today include the addition of a moderate risk of TC formation in the eastern Pacific, consistent with NHC’s latest guidance. This system was expected to be shear limited, but conditions now appear more favorable for the development of at least a weak TC over the next few days. The shape in the West Pacific was modified to reflect the latest model guidance. Confidence in this region is fairly low, though sufficient to warrant continuing the moderate shape. Very little adjustment was made to the Week-2 TC outlook, with late season cyclogenesis still favored over the eastern Pacific as the large- scale circulation becomes more favorable. Precipitation shapes were updated to reflect the latest model consensus between the CFS and ECMWF guidance. The frontal intrusion into the subtropics over southern North America is still expected to be a focal point for enhanced precipitation.
    [Show full text]
  • Evidence of Rising and Poleward Shift of Storm Surge in Western North
    PUBLICATIONS Journal of Geophysical Research: Oceans RESEARCH ARTICLE Evidence of rising and poleward shift of storm surge in western 10.1002/2016JC011777 North Pacific in recent decades Key Points: Lie-Yauw Oey1,2 and Simon Chou1 Storm surge can potentially become more intense and variable as the 1 2 climate warms Graduate Institute of Hydrological & Oceanic Sciences, National Central University, Taoyuan, Taiwan, Program in We give evidence of rising and Atmospheric & Oceanic Sciences, Princeton University, Princeton, New Jersey, USA poleward shift of storm surge in western North Pacific We relate the rising and poleward- Abstract Recently, there has been considerable interest in examining how sea-level extremes due to storm shifting surges to recurving and slower typhoons caused by surge may be related to climate change. Evidence of how storm-surge extremes have evolved since the start of weakening steering flow due to the most recent warming of mid-1970s and early 1980s has not been firmly established however. Here we use climate change 64 years (1950–2013) of observations and model simulations, and find evidence of a significant rise in the inten- sity as well as poleward-shifting of location of typhoon surges in the western North Pacific after 1980s. The rising Supporting Information: and poleward-shifting trends are caused by the weakening of the steering flow in the tropics, which is related Supporting Information S1 to climate warming, resulting in slower-moving and longer-lasting typhoons which had shifted northward. Correspondence to: L. Oey, [email protected] 1. Introduction Citation: Oey, L-Y., and S. Chou (2016), Approximately 60% of all tropical cyclones (TCs; or typhoons) that originate over the warm pool of the western Evidence of rising and poleward shift North Pacific Ocean traverse west and northwestward across 130E (Fig.
    [Show full text]