Informatics Publishing Limited

M. Mohapatra ¹, B. Geetha ¹, Monica Sharma ¹

Affiliations
1 India Meteorological Department, Mausam Bhavan, Lodhi Road, New Delhi 110 003, IN

Abstract

Over the North Indian Ocean (NIO) basin, the uncertainty in tropical cyclone (TC) track forecast is depicted by constructing a cone of uncertainty (COU) around the forecast track for the benefit of disaster managers in their decision-making, especially with respect to area of evacuation. The COU is constructed by drawing a tangent to the circles with the radii equal to average track forecast errors during the past five years for forecast times of 12, 24, 36, …, up to 120 h. The COU which is revised periodically to reflect the track forecast accuracy, has been recently revised by India Meteorological Department (IMD) from the post-monsoon season of 2014. Hence, a study has been undertaken to evaluate this newly introduced COU forecast by IMD. The revised radii used to construct the COU have shrunk by 20-30% due to improved TC track forecast in the recent years (2009-2013). For the new COU, the radii of circles for 24, 48, 72, 96 and 120 h forecasts are 65, 105, 140, 170 and 200 nm respectively, against 80, 135, 185, 235 and 285 nm for the previous COU (2009-2013). The accuracy of the newly constructed forecast COU is 70-80% and is comparable with those of other leading TC forecasting centres in the world.

Keywords

Cone of Uncertainty, Forecast, Ocean Basin, Track, Tropical Cyclone.

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D. R. Pattanaik ¹, M. Mohapatra ¹

Affiliations
1 Director General of Meteorology, India Meteorological Department, New Delhi 110 003, IN

Abstract

Associated with strong El Nino, the southwest monsoon rainfall over India during June to September 2015 was deficit, while the northeast monsoon (NEM) during October to December 2015 over the southern peninsula was very active, particularly during November and early December. Associated with the active phases of NEM, southeast India, especially Tamil Nadu (TN) and Puducherry experienced unprecedented rainfall activity leading to devastating floods over TN, with the megacity of Chennai being the worst affected. The present study discusses the performance of operational extended range forecast (ERF) up to three weeks of this unprecedented NEM rainfall activity over the southern peninsula and TN using the bi-model average (BMA) ERF based on outputs from the Japan Meteorological Agency Ensemble Prediction System and National Centre for Environmental Prediction's (NCEP's) latest version of Climate Forecast System (CFSv.2) coupled model. The BMA forecast captured the likely delay in the onset of NEM over meteorological (met) subdivision TN and associated weak phase of monsoon during October 2015. Similarly, the BMA forecasts also captured the active phases of NEM during November and early December 2015. Although it is difficult to capture the actual magnitude of observed high-rainfall departure over a smaller domain of met-subdivision scale, the BMA-based ERF could capture the active phase of NEM over southern peninsular India, including the metsubdivision TN with a lead time of 1-2 weeks. Quantitatively, the excess NEM rainfall spells during 2015 and particularly that during 5-11 November and 12-18 November 2015 are reasonably well captured in the BMA forecast, although forecast rainfall departure was lower than the actual departure.

Keywords

Bi-Model Average, Climate Forecast System, Extended Range Forecast, Floods, Northeast Monsoon.

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Subimal Ghosh ¹, Subhankar Karmakar ², Anamitra Saha ¹, Mohit Prakash Mohanty ³, Shees Ali ¹, Satya Kiran Raju ⁴, Vrinda Krishnakumar ¹, Maneesha Sebastian ¹, Manasa Ranjan Behera ¹, R. Ashrit ⁵, P. L. N. Murty ⁶, K. Srinivas ⁶, B. Narasimhan ⁷, Tune Usha ⁴, M. V. Ramana Murthy ⁴, P. Thiruvengadam ¹, J. Indu ¹, D. Thirumalaivasan ⁸, John P. George ⁵, S. Gedam ⁹, A. B. Inamdar ⁹, B. S. Murty ⁷, P. P. Mujumdar ¹⁰, M. Mohapatra ¹¹, Arun Bhardwaj ¹², Swati Basu ¹², Shailesh Nayak ¹³

Affiliations
1 Department of Civil Engineering, Indian Institute of Technology Bombay, Mumbai 400 076, IN
2 Interdisciplinary Program in Climate Studies, Indian Institute of Technology Bombay, Mumbai 400 076, IN
3 Environmental Science and Engineering, Indian Institute of Technology Bombay, Mumbai 400 076, IN
4 National Centre for Coastal Research, NIOT Campus, Velacherry–Tambaram Main Road, Pallikaranai, Chennai 600 100, IN
5 National Centre for Medium Range Weather Forecasting, Ministry of Earth Sciences, Government of India, A-50, Sector-62, Noida 201 309, IN
6 Indian National Centre for Ocean Information Services, Pragathi Nagar (BO), Nizampet (SO), Hyderabad 500 090, IN
7 Department of Civil Engineering, Indian Institute of Technology Madras, Chennai 600 036, IN
8 Institute of Remote Sensing, Anna University, Chennai 600 040, IN
9 Centre of Studies in Resources Engineering, Indian Institute of Technology Bombay, Mumbai 400 076, IN
10 Department of Civil Engineering, Indian Institute of Science, Bengaluru 560 012, IN
11 India Meteorological Department, New Delhi 110 003, IN
12 Office of the Principal Scientific Adviser to the Government of India, Vigyan Bhavan Annexe, Maulana Azad Road, New Delhi 110 011, IN
13 National Institute of Advanced Studies, Indian Institute of Science Campus, Bengaluru 560 012, IN

Abstract

Floods are the most common and recurring natural hazards faced by humans since time immemorial. They pose a severe threat to the population, environment and economy in many places across the world, especially urban areas. Urbanization caused due to increasing migration into the floodplains has substantially increased the trend of devastation due to floods in a developing country like India. In Chennai and the surrounding suburban areas, torrential rainfall associated with low-pressure systems engulfed the city during December 2015, affecting more than 4 million people along with economic damages that cost around 3 billion USD.

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M. Mohapatra ¹, A. K. Mitra ¹, Virendra Singh ¹, S. K. Mukherjee ¹, Kavita Navria ², Vikram Prashar ¹, Ashish Tyagi ¹, Atul Kumar Verma ¹, Sunitha Devi ¹, V. S. Prasad ³, Mudumba Ramesh ⁴, Raj Kumar ⁵

Affiliations
1 National Meteorological Satellite Centre, India Meteorological Department, New Delhi 110 003, IN
2 National Meteorological Satellite Centre, India Meteorological Department, New Delhi 110 003ii
3 National Centre for Medium Range Weather Forecasting, Noida 201 309, IN
4 Master Control Facility, Indian Space Research Organisation, Hassan 573 201, IN
5 Space Applications Centre, Indian Space Research Organisation, Ahmedabad 380 015, IN

Abstract

In order to observe severe weather conditions during cyclones, thunderstorms, etc., IMAGER instruments on-board INSAT3D/3DR have been built with a flexible scanning feature known as ‘rapid scan mode’. Using this feature, the number of scan lines over a given coverage region and the number of repetitions of the selected region can be programmed for scanning. Therefore, to understand the physical processes involved in convective clouds associated with severe weather phenomena, rapid scan of INSAT3DR mode is attempted. It has very high temporal resolution of approximately 4 min and 30 sec. The present study will help in better understanding of the physical processes of severe weather phenomena and in nowcasting. It will also help to improve the accuracy in the NWP model forecast through assimilation of radiances and atmospheric motion wind determined using rapid scan mode.

Keywords

Nowcasting, Physical Processes, Rapid Scan Operations, Severe Weather Conditions, Weather Monitoring.

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S. D. Kotal ¹, Soma Sen Roy ², R. S. Sharma ³, M. Mohapatra ²

Affiliations
1 Meteorological Centre Ranchi, Ranchi, Jharkhand 834 002, IN
2 India Meteorological Department, New Delhi 110 003, IN
3 Meteorological Centre Jaipur, Jaipur 302 029, IN

Abstract

Effective nowcasting for thunderstorms has been a challenge to operational forecasters in Jharkhand, India as lightning strikes-related deaths are significantly high. Extrapolation of radar echoes is the very foundation of nowcasting. Multiple radar mosaic data are able to pick out the size, shape, intensity, speed and direction of movement of individual storms on a continuous basis. This makes it possible to determine the likely location of a moving storm by extrapolation. This article demonstrates a new approach of locationspecific nowcast and SMS (short message service)- based dissemination system for thunderstorm and lightning warning up to 3 h ahead over Jharkhand. There are three components of the system. First, identification of the initial development and tracking of thunder cells by mosaic composite reflectivity data from multiple radars. The future location of thunder cells, and their growth or dissipation in terms of radius is estimated by extrapolation using their past trends. Secondly, based on this forecast information, an SMS is generated by the web-based GIS portal of Jharkhand Space Applications Centre for the forecast location and sent to the concerned state officials and mobile service providers over that region. Finally, the warning SMS is sent to all the active mobile users over that region at that time. The system combining nowcasting and dissemination of warning directly to the likely affected people is expected to be more robust considering its effectiveness in the reduction of human casualty.

Keywords

Dissemination System, Lightning, Nowcast, Short Message Service, Thunderstorm.

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