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Improvement of displacement error of rainfall and wind field forecast associated with landfalling tropical cyclone AMPHAN

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Tropical Cyclone Research and Review 2022年第3期11卷 146-162页

作者： s.d.kotal s.K.Bhattacharya India Meteorological department Ministry of Earth science Government of IndiaNew DelhiIndia

spatial distribution of rainfall and wind speed forecast errors associated with landfalling tropical cyclones(TC)occur significantly due to incorrect location forecast by numerical *** major areas of errors are:(i)over-estimation over the model forecast locations and(ii)underestimation over the observed locations of the TCs.A modification method is proposed for real-time improvement of rainfall and wind field forecasts and demonstrated for the typical TC AMPHAN over the Bay of Bengal in *** proposed method to improve the model forecasts is a relocation method through shifting of model forecast locations of TC to the real-time official forecast locations of India Meteorological department(IMd).The modification is applied to the forecasts obtained from the operational numerical model,the Global Forecast system(GFs)of *** of the proposed method shows considerable improvement of both the parameters over both the *** rainfall forecast errors due to displacement are found to have improved by 44.1%–69.8%and 72.1%–85.2%over the GFs forecast locations and over the observed locations respectively for the respective forecast lead times 48 h,72 h,and 96 ***,the wind speed forecasts have improved by 27.6%–56.0%and 63.7%–84.6%over the GFs forecast locations and over the observed locations respectively for the respective forecast lead times 60 h,72 h,and 84 *** results show that the proposed technique has capacity to provide improved spatial distributions of rainfall and wind speed forecasts associated with landfalling TCs and useful guidance to operational forecasters.

关键词： Tropical cyclone Track forecast Rainfall forecast Wind field spatial distribution North Indian ocean

Forecasting of tropical cyclones AsANI(2022)and MOCHA(2023)over the Bay of Bengal-real time challenges to forecasters

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Tropical Cyclone Research and Review 2024年第2期13卷 88-112页

作者： s.d.kotal T.Arulalan M.Mohapatra India Meteorological department Ministry of Earth ScienceGovernment of IndiaNew DelhiIndia

This study examines the track and intensity forecasts of two typical Bay of Bengal tropical cyclones(TC)AsANI and *** analysis of various Numerical Weather Prediction(NWP)model forecasts[ECMWF(European Centre for Medium range Weather Forecast),NCEP(National Centers for Environmental Prediction),NCUM(National Centre for Medium Range Weather Forecast-Uniﬁed Model),IMd(India Meteorological department),HWRF(Hurricane Weather Research and Forecasting)],MME(Multi-model Ensemble),sCIP(statistical Cyclone Intensity Prediction)model,and OFCL(Ofﬁcial)forecasts shows that intensity forecasts of AsANI and track forecasts of MOCHA were reasonably good,but there were large errors and wide variation in track forecasts of AsANI and in intensity forecasts of *** all model forecasts,the track forecast errors of IMd model and MME were least in general for AsANI and MOCHA ***,the landfall point forecast errors of IMd were least for AsANI,and the MME and OFCL forecast errors were least for *** model is found to be consistently better for landfall time forecast for AsANI,and the errors of ECMWF,IMd and HWRF were least and of same order for *** intensity forecast errors of OFCL and sCIP were least for AsANI,and the forecast errors of HWRF,IMd,NCEP,sCIP and OFCL were comparable and least for MOCHA up to 48 h forecast and HWRF errors were least thereafter in *** ECMWF model forecast errors for intensity were found to be highest for both the *** results also show that although there is signiﬁcant improvement of track forecasts and limited or no improvement of intensity forecast in previous decades but challenges still persists in real time forecasting of both track and intensity due to wide variation and inconsistency of model forecasts for different TC cases.

关键词： Tropical cyclone Track forecast Intensity forecast NWP model Bay of Bengal North Indian Ocean

EVOLUTION OF THERMOdYNAMIC sTRUCTUREs dURING RAPId GROWTH ANd dECAY OF EXTREMELY sEVERE CYCLONIC sTORM CHAPALA(2015)

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Tropical Cyclone Research and Review 2017年第3期6卷 67-81页

作者： s.d.kotal s.K.BHATTACHARYA India Meteorological department

The structure and evolution of inner-core convective bursts and their differences associated with rapid intensification(RI) and rapid decay(Rd) of tropical cyclone CHAPALA are examined. The inception of RI was associated with substantial increase of convective heating and its vertical extent in the inner core. Increase in diabatic heating was of the order of 12-21 oC, particularly in the middle and upper troposphere. Latent heat release produced a diabatically generated potential vorticity(PV) in vertical column. The immediate cause of RI was a significant increase of moisture flux from surface to 500 h Pa. This was accomplished primarily by updrafts of the order of 6-12 Pa s-1, representing the strong vertical motion distribution inside the warm core convective zone. The episode of deep convective bursts transpired during the period of RI. The evolving flow became highly symmetric and dominated by deep convective axisymmetric vortex structures. The Rd coincided with the significant weakening in updraft of moisture flux consequently decrease of diabatic heating in the middle and upper troposphere and dissipation of upper and lower PV.

关键词： tropical cyclone rapid intensification rapid decay potential vorticity latent heat diabatic heating Arabian sea

sOME sPECIAL CHARACTERIsTICs OF TRACK ANd INTENsITY OF TYPHOONs OVER THE WEsTERN NORTH PACIFIC

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Tropical Cyclone Research and Review 2017年第3期6卷 82-93页

作者： TARAsHA KHURANA s.K.BHATTACHARYA s.d.kotal Netaji subhas Institute of Technology India Meteorological department NWP Division

Joint Typhoon Warning Center(JTWC) Best Track data from 1995 to 2014 are processed to examine some specific patterns and trends shown by Typhoons over the Western North Pacific. With a multivariate dataset of 588 TC cases in hand, we carry out a sub-domain analysis by dividing the Western North Pacific region into domains of 2°x2° and find the preferred regions of genesis, favourable direction of movement, steep recurvature, rapid intensification, and rapid decay. The region from longitude 132°E to 134°E and latitude 16°N to 18°N showed the highest number of cases(19) for rapid intensification(RI) and a general pattern is found that the RI systems occurred mostly in the later half of the year with a negative Pacific decadal Oscillation(PdO) index. similarly, the domain from longitude 114°E to 116°E and latitude 26°N to 28°N had the highest probability of 0.857 for rapid decay. The probabilities of recurvature for each sub-domain were calculated for angles 30°, 45°, 60°, 90°, 120° and 150°. The sub-domain around longitude 118°E and latitude 12°N had the steepest recurve of 168.69°. It also had a high probability of 0.714 for a recurvature of greater than 90°. The most taken direction of movement of typhoons around the Western North Pacific were analysed in different ways and along the 16 points of compass, the direction from 270° to 292.5° was found to be the most preferred direction of movement.

关键词： typhoons Western North Pacific genesis track recurvature intensity rapid intensification rapid decay sub-domain PdO index

APPLICATION OF FUZZY CLUsTERING TECHNIQUE FOR ANALYsIs OF NORTH INdIAN OCEAN TROPICAL CYCLONE TRACKs

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Tropical Cyclone Research and Review 2015年第3期4卷 110-123页

作者： sANKAR NATH s.d.kotal P.K.KUNdU India Meteorological DepartmentNew DelhiIndia department of Mathematics Jadavpur UniversityKolkataIndia

A fuzzy, c-means(FCM) clustering technique is explored to investigate the track of tropical cyclones over the North Indian Ocean(NIO) for the period(1976-2014). A total of fi ve clusters is objectively identifi ed based on partition index,partition coeffi cient, dunn Index and separation index. The results obtained during analysis emphasized that each cluster has the unique features in terms of their genesis location, landfall, travel duration, trajectory, seasonality, accumulated cyclone energy and Intensity. Analysis of large scale environmental parameters, constructed preceding day of genesis show some of these parameters to be potential precursors to TC formation for almost all the clusters, most prominently, mid-tropospheric humidity, zonal wind,vorticity and outgoing long wave radiation of the main developing regions. The individual clusters have the several distinct features in their seasonal *** cluster C5 shows distinct bimodal distributions where as other clusters are formed throughout the year. ENsO infl uenced the cyclone frequency in two of the fi ve clusters. The MJO is found to play an important role in the genesis of the cyclone. The post monsoon season cyclone frequency is more in MJO phase 2, 3 and 4. The technique(FCM) can be used as a guideline in terms of the probable affected zone of TC Tracks by the operational forecasters.

关键词： tropical cyclone North Indian Ocean cluster analysis fuzzy c-means clustering

dEVELOPMENT OF NWP BAsEd OBJECTIVE CYCLONE PREdICTION sYsTEM(CPs) FOR NORTH INdIAN OCEAN TROPICAL CYCLONEs——EVALUATION OF PERFORMANCE

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Tropical Cyclone Research and Review 2014年第3期3卷 162-177页

作者： s.d.kotal s.K.BHATTACHARYA s.K.ROY BHOWMIK India Meteorological department

An objective NWP based Cyclone Prediction system(CPs) has been developed and implemented at IMd for operational cyclone forecasting over the north Indian Ocean(NIO). The five forecast components of CPs are(a) Genesis Potential Parameter(GPP),(b) Multi-Model Ensemble(MME) technique for track prediction,(c) statistical Cyclone Intensity Prediction(sCIP),(d) rapid intensification and(e) decay model to forecast intensity after the *** shows GPP had higher probability of detection(0.98) and lower false alarm ratio(0.27) with higher critical success index(0.72). Mean track error of MME ranged from 74 km at 12 h to 200 km at 72 h and reduced by 27% to 52% for 36 h to 72 h forecast during 2009-2013. The mean forecast errors of landfall position ranged from 56 km at 24 h to 137 km at 72 h and landfall time error ranged from 3.6 h at 24 h to 6.1 h at 72 h. Mean intensity errors of sCIP ranged from 5.4 kt at 12 h to 16.9 kt at 72 h. The probabilistic rapid intensification forecast was skillful compared to climatology. The 6-hourly decaying intensity(after landfall) errors ranged from 3 kt to 4.9 kt. Results demonstrate the potential of CPs for operational cyclone forecast over the NIO.

关键词： tropical cyclone Cyclone Prediction system (CPs) forecast verification North Indian Ocean

AN ANALYsIs OF RECURVATURE ANd dECAY OF THE TROPICAL CYCLONE ‘MAdI’(2013) OVER THE BAY OF BENGAL

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Tropical Cyclone Research and Review 2015年第1期4卷 27-37页

作者： s.K.BHATTACHARYA s.d.kotal P.K.KUN dU India Meteorological department,NWP division department of Mathematics,Jadavpur University India Meteorological department NWP Division department of Mathematics Jadavpur University

The track of tropical cyclone‘Madi’showed almost 180° turn around,while immediately after recurvature it decayed rapidly in the following 24 *** surface temperature(ssT)analyses rule out confrontation with low ssT as cause of *** 0000 UTC of 9 december 2013 diabatic heating(dH),potential vorticity(PV)and vertical wind shear(VWs)were favourable for ***,a dry area close to the system centre at mid-troposphere subsequently engulfed the middle strata and the mid-tropospheric relative humidity(MTH)drastically reduced on 0000 UTC of 10 december *** MTH further reduced on 0000 UTC of 11 december *** of moisture in mid-troposphere apparently caused a mutation within the structure causing a sudden decrease in *** the system dried up,reduction in convection above 400 h Pa hindered latent heat *** above 400 h Pa decreased ***,there was a spurt of VWs at 1200 UTC of the 10december *** opposite wind flow between lower level and upper level whisked away the top of the system to *** the influence of the net northeasterly flow in lower to middle troposphere,the miniature vortex recurved southwestward and the vertical distortion due to shear weakened the system into a depression.

关键词： decay recurvature mid-tropospheric humidity steering current

OPERATIONAL PERsPECTIVEs ON TROPICAL CYCLONE INTENsITY CHANGE PART 1:RECENT AdVANCEs IN INTENsITY GUIdANCE

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Tropical Cyclone Research and Review 2019年第3期8卷 123-133页

作者： Joseph B.Courtney sébastien Langlade Charles R.sampson John A.Knaff Thomas Birchard stephen Barlow s.d.kotal Tarik Kriat Woojeong Lee Richard Pasch Udai shimada Bureau of Meteorology Australia Meteo-France La RéunionFrance Naval Research Laboratory(NRL) USA NOAA/Center for satellite Applications and Research USA Central Pacific Hurricane Centre(CPHC) USA Joint Typhoon Warning Centre(JTWC) USA India Meteorological department(IMd) India Korea Meteorological Administration(KMA) Korea National Hurricane Centre(NHC) USA Japanese Meteorological Agency(JMA) Japan

This review summarizes techniques used by operational centers to forecast tropical cyclone intensity change as presented to the International Workshop on Tropical Cyclones(IWTC-9)in Hawaii in *** advances and major changes over the past four years are presented,with a special focus on forecasting rapid intensity *** intensity change remains one of the most difficult aspects of tropical cyclone forecasting,objective guidance has shown some *** greatest improvements are realized when consensus methods are utilized,especially those that blend statistical-dynamical based guidance with dynamical ocean-coupled regional *** models become even more skillful when initialized with inner core observational *** improvement and availability of intensity guidance along with associated forecaster training are expected to deliver forecasting improvements in the future.

关键词： tropical cyclone intensity change rapid intensification

OPERATIONAL PERsPECTIVEs ON TROPICAL CYCLONE INTENsITY CHANGE PART 2:FORECAsTs BY OPERATIONAL AGENCIEs

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Tropical Cyclone Research and Review 2019年第4期8卷 226-239页

作者： Joseph B.Courtney sébastien Langlade stephen Barlow Thomas Birchard John A.Knaff s.d.kotal Tarik Kriat Woojeong Lee Richard Pasch Charles R.sampson Udai shimada Amit singh Bureau of Meteorology Australia Meteo-France La RéunionFrance Joint Typhoon Warning Centre(JTWC) USA Central Pacific Hurricane Centre(CPHC) USA NOAA/Center for satellite Applications and Research USA India Meteorological department(IMd) India Meteo-France France Korea Meteorological Administration(KMA) Korea National Hurricane Centre(NHC) USA Naval Research Laboratory(NRL) USA Japanese Meteorological Agency(JMA) Japan Fiji Meteorological service(FMs) Fiji

This review summarizes experiences at operational centers to forecast tropical cyclone(TC) intensity change as presented to the International Workshop on Tropical Cyclones(IWTC-9) in Hawaii in 2018. some operational forecast centers have been able to leverage advances in intensity guidance to increase forecast skill, albeit incrementally, while others have struggled to make any significant improvements. Rapid intensity changes continue to present major challenges to operational centers and individual difficult cases illustrate the forecasting *** is noteworthy that the realization of a recommendation from IWTC-8 in 2014, to adapt guidance initially developed for the North Atlantic and North-East Pacific to other basins, has led to improved forecast skill of some agencies. Recent worldwide difficult cases are presented so that the research community can further investigate, potentially leading to improved intensity forecasts when similar cases are observed in the future.

关键词： tropical cyclone intensity change rapid intensification