31 May 2012

Delay in Rain Forecast

Minister of State in the Ministry of Planning, Minister of State in the Ministry of Science and Technology and Minister of State in the Ministry of Earth Sciences Dr Ashwani Kumar today stated in Rajya Sabha that IMD issues monsoon season rainfall forecast for the country as a whole in two stages-in April and in June. Generally, April forecast is issued in the second half of the month as required global data measured up to end of March is the critical forecast analysis/assessment and such data becomes available only around 10th April. In reply to a question the Minister pointed out that in recent years, IMD also utilizes experimental/operational rainfall forecasts along with projected sea surface temperature anomalies and more so El-Nino Predictions from many global climate centres for wider scrutiny and analysis and such inputs are updated normally during 15th - 25th of every month. Depending upon the availability of these global inputs, IMD had to adjust the date of issue of monsoon season rainfall forecast for the country. 
The Minister further stated that factors for the perceived delay cannot be the reason for the delay in issuing monsoon season rainfall forecast for the country. In fact, SACOF-3 outlook for the south Asian region is finalized with the IMDs lead role only and after its establishment India has been hosting the SACOF Meetings for the last 3-years in succession as our south Asian partners do not have the institutional mechanisms to generate seasonal rainfall forecast outlook. Outlining the forecast basis the Minister described various models as follows: 
(i) As the seasonal rainfall outlook for the SACOF region for 2012 monsoon season has shown large divergence, ranging from deficient rainfall to normal/excess rainfall from various sources both from India and abroad viz. Japan Agency for Marine-Earth Science and Technology (JAMSTEC) and National Centers for Environmental Prediction (NCEP), USA indicated normal and below normal for most parts of the country based on two versions of the model. While the multi-model forecast from European Center for Medium Range Weather Forecasts (ECMWF), UK prepared based on coupled models of ECMWF, UKMO and Meteo France indicated normal to above normal rainfall over most parts of the country. 
(ii)The El Nino-Southern Oscillation (ENSO) conditions over equatorial Pacific, significantly influences the performance of the monsoon season rainfall which was in transition phase from weak La Nina to neutral conditions. The latest forecasts from both statistical and dynamical models suggested 53% probability for continuation of neutral ENSO conditions during the monsoon season and about 39% probability for emergence of El Nino conditions during later part of the season. Therefore, things will become clear only after May. That is why IMD also updates its monsoon forecast in June after accounting for all these factors. 

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