IMD to use three models to better weather forecasts

Pune: For more accurate weather forecasts in 2021, the India Meteorological Department (IMD) will be using data from three weather prediction models.

Speaking at the annual monsoon e-workshop and national e-symposium on “Cloud and Precipitation Processes” on Monday, DS Pai, scientist and head, climate research and services, IMD, Pune, said the three models will be used by the weather department to ensure that the predictions are more detailed and accurate.

Pai said the three models will forecast monsoon based on various factors.

“A multi-model ensemble (MME), the Nigam model developed by professor Sumant Nigam and his team from the University of Maryland, US, and MME forecast based on calibrated rainfall forecasts obtained through principal component regression models of different observed climate variables prior to the monsoon season will be used to forecast the weather system in 2021,” said Pai.

Pai said that various models have been used to forecast rainfall during the southwest monsoon in the last decade.

“For 2020, southwest monsoon forecast by models were indicating heavy rainfall. However, the seasonal rainfall was relatively less, but near to normal. Expect for July 2020, the rainfall predicted by IMD was underestimated in most months. However, we upgraded the forecast. We observed weak La Nina conditions likely during the late monsoon of 2020. This affected the rainfall system and we were able to forecast that correctly,” said Pai.

He said that the weather department has several models which are rainfall calibrated and some predict in a particular way.

“The deficiency of one model can be fulfilled by other models. For example, in 2020, 102 per cent of rainfall was forecasted, but the observation was 109 per cent. Such discrepancies can be avoided by using a multi-model approach for forecast,” said Pai.

Pai said that 2020 did not see a single monsoon depression, but only excess monsoon with many low pressure systems.

“There are two reasons to this. One was that the system formed was very close to the coast and entered into land very quickly. Second is that the easterly jet was very strong which did not allow any system to develop,” said Pai.

Jet streams are strong winds that can push air masses around and affect weather patterns, according to the weather officials.