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GOVERNMENT OF INDIA IMD Met. Monograph No. : MINISTRY OF EARTH SCIENCES Synoptic Meteorology No. 10/2011 INDIA METEOROLOGICAL DEPARTMENT Monsoon 2010 AA RReeppoorrtt Edited by Ajit Tyagi, A. B. Mazumdar and D. S. Pai Monsoon 2010 AA RReeppoorrtt DESIGNED & PRINTED AT OAOTHDFFE DFMI ICMTEIEETO ETONEOFAOR LTRO HDOLEIROLOEGCGYTI C(ORAREL S GOEEFANFREICCREHA )PL,P RUENSES, NDIIA METEOROLOGICAL DEPARTMETN ADNDAITTIIOONNOAAFLLF DICCILREIE MOCAFTT OTEHR CE GEENNTREREAL NATIONAL CLIMATE CENTRE OF METEOROLOGY (RESEARCH),PUNE NATIONAL CLIMATE CENTRE IMD Met Monograph: Synoptic Meteorology No: 10/2011 Government of India India Meteorological Department Edited by Ajit Tyagi, A. B. Mazumdar and D. S. Pai National Climate Centre India Meteorological Department PUNE- 411 005 INDIA Copyright © India Meteorological Department, 2011 The right of publication in print, electronic or any other form reserved by the India Meteorological Department. Short extracts may be reproduced, however the source should be clearly indicated. DISCLAIMER & LIMITATIONS The contents published in this report have been checked and authenticity assured within limitations of human errors. India Meteorological Department is not responsible for any errors and omissions. The geographical boundaries shown in this report do not necessarily correspond to the political boundaries. List of Authors Ajit Tyagi Director General of Meteorology, India Meteorological Department A. B. Mazumdar Additional Director General of Meteorology (Research), India Meteorological Department, Pune Ananda Kumar Das, V.R. Durai, Office of the S.D. Kotal, M Mohapatra, Naresh Director General of Meteorology, Kumar, D. R. Pattanaik, S.K. Roy India Meteorological Department, New Delhi Bhowmik, O. P. Singh, C. S. Tomar, B. P. Yadav D. S. Pai, O.P. Sreejith and A.K. Office of the Srivastava Additional Director General of Meteorology (Research), India Meteorological Department, Pune Medha Khole, Sunitha Devi. S. Office of the DeputyDirector General of Meteorology (Weather Forecasting) India Meteorological Department, Pune Manish Ranalkar Office of the DeputyDirector General of Meteorology (Surface Instruments) India Meteorological Department, Pune C o n t e n t s Acknowledgements Preface Executive Summary Chapter- 1 Onset, advance and withdrawal of southwest monsoon Chapter- 2 Semi Permanent Systems and Synoptic Features Chapter- 3 Rainfall Statistics Chapter- 4 Global and Regional Circulation Anomalies Chapter- 5 Performance of Operational NWP Short Range Forecasts – Southwest Monsoon 2010 Chapter- 6 Performance of Global Forecast System of IMD In the Medium Range Time Scale During Summer Monsoon 2010 Chapter- 7 Performance of Extended Range Forecast during Southwest Monsoon 2010 Chapter- 8 Verification of the operational and experimental Long Range Forecasts Chapter- 9 Features of Southwest Monsoon -2010 as observed In Satellite Products Chapter- 10 Utility of Automatic Weather Station (AWS) data for monitoring and prediction of Cyclonic Disturbances during 2010 Chapter- 11 Summary and Conclusions ACKNOWLEDGEMENTS The editorial team could complete this report in time and in detail only due to the whole hearted support of all the authors and co-authors of various chapters of this report. The editorial team expresses sincere thanks to all of them. The report was prepared in the Office of the ADGM(R), IMD, Pune. The officers and staff of the Long Range Forecasting Section and National Climate Center provided the technical assistance. We are particularly thankful to Shri. S. M. Jamadar, Smt. Madhuri Musale, Smt. Latha Sridhar, Shri. C.N. Shaligram, and Shri. Bhushan Patkar for their technical support. We are also thankful to Shri. Philipose Abraham and other staff members of the Printing and Documentation Section of the Office of ADGM(R), IMD, Pune for designing, type setting and printing and publication of the report. Our sincere thanks are also due to the officers and staff of DGM (Hydromet), New Delhi for providing the station rainfall data extensively used in this report. PREFACE The 2010 southwest monsoon season was a normal monsoon season with the season (June-September) rainfall over the country as a whole of 102% of its long period average (LPA). Out of the total 36 meteorological subdivisions, 31 subdivisions constituting 85% of the total area of the country received excess/normal season rainfall and the remaining 5 subdivisions (15% of the total area of the country) received deficient season rainfall. The monthly rainfall over the country as a whole during all the months of the season except June was above the LPA value. The monsoon set in over Kerala on 31st May, one day earlier than its normal date of 1st June and covered the entire country by 6th July, earlier than its normal date of 15th July. However, the withdrawal of monsoon from west Rajasthan was delayed and it commenced only on 27th September compared to its normal date of 1st September. After 2002 (a deficient monsoon year), this was the only year when no depressions formed over the Indian monsoon region during the entire season. The monsoon rainfall was impacted by the different regional and global features such as moderate to strong La Niña conditions over equatorial Pacific, weak negative Indian Ocean Dipole and strong activities of Madden Julian Oscillations in the equatorial Indian Ocean. The mid latitude wave activities north of Indian region had also significant bearing on the rainfall distribution over the country. Thus the 2010 monsoon season witnessed many anomalous rainfall and circulation features which call for more focused studies for improving our understanding of monsoon and its predictability. The main objective of bringing out the monsoon monographs every year is to document various challenging aspects of each monsoon for quick reference to both operational and research communities. The present report has been divided in different chapters each of which discusses specific aspects of the 2010 southwest monsoon like progress and withdrawal of monsoon, synoptic systems over the Indian region, large scale regional and global thermal, circulation and convective features observed during the season, rainfall statistics, forecasts at various scales and its verification etc. The report also includes chapters on the utility of the satellite and automatic weather station data in monitoring and prediction of monsoon. There is no doubt that this report provides useful and authentic information about the 2010 southwest monsoon season. I sincerely appreciate all the authors for their valuable contribution. I also appreciate the efforts made by Dr. D. S. Pai and other officers/ staff of the office of the ADGM(R ), IMD, Pune in bringing out this met. monograph, which is sixth in the series of monographs. Ajit Tyagi Director General of Meteorology India Meteorological Department Executive Summary 1 Document title Monsoon 2010 Report 2 Document type Meteorological Monograph 3 Issue No. Synoptic Meteorology No.10/2011 4 Issue date 17.02.2011 5 Security Classification Unclassified 6 Control Status Unclassified 7 Document type Scientific Report 8 No. of Pages 212 9 No. of Figures 131 10 No. of references 28 11 Distribution Unrestricted 12 Language English 13 Editors Ajit Tyagi, A. B. Mazumdar and D. S. Pai Originating National Climate Centre, Office of ADGM (R), India 14 Division/Group Meteorological Department, Pune Reviewing and Director General of Meteorology, India Meteorological 15 Approving Authority Department, New Delhi. Operational Forecasters, Modelers and Researchers, 16 End users Government Officials etc. The 2010 southwest monsoon was a normal with season rainfall of 102% of long period average (LPA) over the county as a whole. Monsoon set over Kerala close to its normal date but covered the entire country nearly one week before the normal date. No break events were observed and no depressions were formed during the season. In association with the evolution of La Nina during the season, the rainfall of the second half of the season was more than that in the first half. Monthly rainfall except in June was above its LPA. The rainfall over most of the subdivisions, except 5 (deficient) 17 Abstract subdivisions over eastern part of the country was normal or excess. Region wise, rainfall over south Peninsula was excess and that over northeast India was deficient. The rainfall over northwest India and central India was normal. The first 10 chapters of this report discusses various important aspects of the 2010 SW monsoon such as the rainfall, regional and global features, verification of forecasts at different temporal and spatial scales, satellite & AWS analysis of the events etc. The summary and conclusions of the report are given in the Chapter 11. Southwest Monsoon, La Niña, Multi-model Ensemble, 18 Key Words Forecast Verification, Rainfall, Satellite Imageries. 1 ONSET, ADVANCE AND WITHDRAWAL OF SOUTHWEST MONSOON Medha Khole, A. B. Mazumdar, Sunitha Devi. S. and B.P. Yadav The Monsoon Onset over Kerala (MOK) and the further advance of the South West monsoon exhibit inter annual as well as intra seasonal variability. The advance of the monsoon is often not very systematic and regular. It is marked by phases of rapid advance and periods of hiatus in the advance. These phases are largely modulated by strength of the south westerly winds [cross equatorial flow] over north Indian Ocean, which, in turn, is governed by placement and intensity of components of monsoon and also the tele- connections of monsoon. This chapter discusses the various meteorological aspects of onset, advance and withdrawal of southwest monsoon 2010. 1.1 Arrival of southwest monsoon current over the Andaman Sea Southwest monsoon set in over the Andaman Sea on 17th May, 3 days prior to normal date in association with a severe cyclonic storm (Laila, 17th–21stMay 2010) over the Bay of Bengal. The southwest monsoon further advanced over parts of Comorin area and some more parts of Bay of Bengal on 21st May and thereafter, there was a hiatus in the monsoon advance lasting for more than a week, due to a temporary weakening of the cross equatorial flow. 1
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