Spring • ANALYSIS • SOUTH-WEST MONSOON Chinchorkar et al. Long Range Forecast of South-West Monsoon Rainfall for 2013 for Different Regions of Gujarat, Spring, 2013, 2(2), 6-9, www.discovery.org.in http://www.discovery.org.in/springjournal.htm © 2013 discovery publication. All rights reserved Page6 Chinchorkar SS 1☼ , Vaidya VB 2 , Vyas Pandey 3 1. Assistant Professor, Polytechnic in Agricultural Engineering, AAU, Muvaliya Farm,Dahod-389151, India 2. Assistant Professor, Department of Agricultural Meteorology, BACA, ,AAU, Anand- 388 110, India 3. Professor and Head, Department of Agricultural Meteorology,BACA, ,AAU, Anand- 388 110, India ☼ Corresponding author: Assistant Professor, Polytechnic in Agricultural Engineering, AAU, Muvaliya Farm, Dahod-389151, Mail: sachin_chinchorkar@yahoo.com Received 16 August; accepted 10 October; published online 01 November; printed 30 November 2013 ABSTRACT The large spatial variability in monsoon rainfall over India demands for regional models for predicting the seasonal rainfall. Hence, models were developed for predicting seasonal (June-September) rainfall of three regions (north, middle and south) of Gujarat using multiple regression technique. The monthly weather data of 30 years of Anand (1980-2009), 22 years (1987-2009) of Navsari and 27 years (1983-2009) of SK Nagar were used. The models were validated with independent data set of four year (2006-2011). The best models were selected based on higher R 2 and lower model error. Four models were obtained; 2 for Anand (middle Gujarat) and one each for SK Nagar (north Gujarat) and Navsari (south Gujarat). Anand (Model-1) has showed 8.5% error (2006 to 2011) while, model-2 shows -0.16% error. S K. Nagar station (North Gujarat) has shown the -3.8% error. Navsari (South Gujarat) station has shown -5.6% error. Since all models have shown less than 10% error, hence above operational models can be used for the rainfall forecast of monsoon. Results suggested that for Model 1 (November to March) is predicting 1054.0 mm (Seasonal normal rainfall is 796.0 mm) higher rainfall than the normal by 32.4%. Model 2 (March to May) is predicting 1454.7mm is higher than normal by +82.7 % (Seasonal Normal 796 mm). For north Gujarat SK Nagar station is predicting 778.5mm rainfall which is more by 31.5% than normal (591.1 mm) . In south Gujarat Navsari station is predicting 1646.6 higher (normal rainfall is 1363.0 mm) by 20.8%. Key words: Multiple regression, rainfall forecasting, rainfall analysis, statistical model. How to cite this article: Chinchorkar SS, Vaidya VB, Vyas Pandey. Long Range Forecast of South-West Monsoon Rainfall for 2013 for Different Regions of Gujarat. Spring, 2013, 2(2), 6-9 1. BACKGROUND South-west monsoon rainfall (received during June to September) determines the fate of dry land farmers as well as the status of national food security in India almost every year. The need for information about south-west monsoon rainfall is great in these areas. An accurate long-range forecast can help farmers increasing agricultural productivity in good rainfall years and negate the sudden downturns in agricultural production during anticipated drought years by giving farmers sufficient time to adopt drought resistant crop varieties and appropriate crop, soil and water management practices. The Indian meteorological Department (IMD) is now able to make all- India long- range forecasts of south-west monsoon rainfall accurately using power regression model based on 16 regional and global parameters from 1988 onwards. The India Meteorological Department (IMD) has been issuing operational long- range forecasts for summer monsoon rainfall for more than one century. Since 1988, the operational forecasts have been issued using the 16 Parameter Power Regression and Parametric models for the summer monsoon rainfall over the country as a whole ANALYSIS • SOUTH-WEST MONSOON Spring, Volume 2, Number 2, November 2013 Spring Long Range Forecast of South-West Monsoon Rainfall for 2013 for Different Regions of Gujarat ☼ SAVE NATURE, SAVE EARTH The International Daily Journal for Climate Change, Global Warming & Sustainability ISSN 2347 – 3800 EISSN 2347 – 3851