Delayed monsoon onset - Part I - Longer wait for Delhi & Telangana

Prof. Dr. Dr. Sc. Elena Surovyatkina is a climate scientist and a leader of monsoon research group at the Potsdam Institute for Climate Impact Research in Potsdam, Germany and a principal researcher at Space Research Institute of Russian Academy of Sciences in Moscow, Russia. Her expertise lies in theoretical physics and in the theory of critical phenomena.

Weather & Radar India interviewed Prof. Surovyatkina regarding the freshly released Forecast of the onset dates of the Indian Summer Monsoon - 2021 over the central part of India, Telangana, and Delhi.

There will be delayed monsoon onset over Central India, Telangana and Delhi. The Indian Summer Monsoon (the Southwest Monsoon) is likely to set over the central part of India, the Eastern Ghats region (20°N,80°E), on the last week of June, between 21 and 29 June 2021. Pre-monsoon isolated rainfall may appear in period 14 -17 June. The continuous monsoon rainfall is expected to start from June 29.

Monsoon research attracts me when we found that the transition from pre-monsoon to monsoon is a critical transition meaning that it is irreversible; there is no way back. Such kinds of phenomena are most interesting for me.

Once temperature passes below a certain threshold, but relative humidity rises over the threshold, a monsoon onset becomes inevitable. Usually, it happens either simultaneously or within a 2-day span. Thus, the range of the days when the conditions appear I define as an onset of monsoon.

Our methodology is different from the numerical weather forecast; it is based on a connection between the process in the atmosphere and the specific geography of the Indian subcontinent. We found a new feature of the Indian summer monsoon wherein two regions in the areas of the Eastern Ghats (EG) and North Pakistan (NP) act as tipping elements, which play a crucial role in the spatial organization of the monsoon. The most interesting feature is how the tipping elements are connected: on the eve of the onset and the withdrawal of the monsoon in the central part of India, the temperature and relative humidity in the two tipping elements become equal. It is a persistent feature that happens every year. Why is it persistent? Because it is defined by geography.

Observations in tipping elements, allow us forecasting of the monsoon onset and withdrawal dates for 40 and 70 days in advance, respectively. Since 2016, I issued a forecast of the monsoon onset and withdrawal 40 days and 70 days in advance, respectively, that´s ten correct forecasts in five years in a row, which show correct results. It is the earliest forecast of the onset date ever made and withdrawal forecast currently the only one available in India!