Agency makes model to forecast rain for 20 days in advance every 5 days

“Only when it is validated by the Indian Meteorological Department, it could become an indigenous model of rain forecast,” IITM senior scientist A K Sahai told The Indian Express. Scientists said it is likely to become operational in the next six months.

A system of predicting rain after every five days for a period of 15-20 days does not exist anywhere in the world, scientists claimed.

“Such a system is already in existence in India. Since 2013, we are putting it out on the IITM website. It is being used by researchers and the IMD,” said Sahai.

The sub-seasonal or extended range prediction (ERP) refers to a meteorological forecast more than 10 days in advance.

“The ERP of active (rainy) and break (dry) phases during the monsoon has tremendous operational importance for agricultural planning, dam management, city planning and management of various similar resources that depend on the spatial-temporal variability of rainfall,” said scientists.

IITM said the importance of ERP has been recognised by the Ministry of Earth Sciences and it has emphasised the development of an ensemble system for dynamic Extended Range Prediction of Active/Break Spells (ERPAS) of Indian summer monsoon (ISM) rainfall under the National Monsoon Mission Project.
For developing the indigenous system, the IITM has relied on the CFS (Climate Forecast System) of US.

“The CFS model (which is a fully coupled ocean atmosphere model) of NCEP, USA has been selected as the basic modelling system for developing a state-of-the-art dynamical prediction system for monsoon rainfall on different time scales at our Institute, IITM. Therefore, all our model developmental activities and forecasts are based on the CFS model,” said Sahai.

Based on the CFS, IITM scientists have come up with four indigenous models.

“Our ERP group at IITM has indigenously developed an Ensemble Prediction System (EPS) based on CFS model for the prediction of monsoon onset over Kerala (MOK), active/break spells and withdrawal of ISM and real-time forecasts. The experimental operational forecasts are being updated at the IITM website in real-time basis since 2013,” he added.