The current phase and amplitude of the Madden-Julian Oscillation (MJO) are not favourable to bring rainfall in the coming week. We take a look at the reasons impacting the progress of monsoon in northern India.
City Express News
New Delhi, Jun, 23,2021:Parts of North India have to wait for the monsoon, with the IMD saying that its further progress into Delhi and parts of Rajasthan, Haryana and Punjab is “unlikely” this week.
The southwest monsoon has so far covered most parts of the country except parts of Rajasthan, Delhi, Haryana and Punjab,” the IMD said in a statement on Tuesday. Here is what is causing the delay:
The Madden-Julian Oscillation (MJO) is one of the dominant modes of intra-seasonal variability in the tropical atmosphere. Its location and amplitude regulates the genesis and intensity of tropical convection and associated circulating features like low-pressure systems over the North Indian Ocean.
Currently, it is lying in Phase one (east Africa) with amplitude greater than one. It is likely to remain the same for the next one week.
Hence, the phase and amplitude of MJO are not favourable to enhance the convection over the North Indian Ocean and bring rainfall over the region in the coming week.
Mid-latitude westerly and weakening of lower-level easterly over northern India
An analysis of numerical weather prediction (NWP) models till June 30 indicates that mid-latitude westerly winds will be dominating North India next week.
A western disturbance or a cyclonic circulation over northern Pakistan and adjoining parts of Jammu and Kashmir is likely to enhance rainfall along the east coast between June 24 and 26.
However, these conditions are not favourable for bringing rainfall over central and northwest India.
Cross equatorial flow over Arabian Sea
Winds over the eastern and central parts of the Arabian Sea have weakened and are currently about 10 to 20 knots along the west coast. Such weak monsoonal winds will prevail for the next seven days.
Low pressure systems
Forecasts based on model consensus show little probability of formation of low-pressure systems over core monsoon areas as well as over the north of Bay of Bengal till June 30, thus, further weakening the lower levels of easterly winds over the northern plains of India.
Forecast and warning
Under the influence of western disturbance in the mid and upper tropospheric westerlies, the current spell of isolated light to moderate rainfall is likely to continue over the Western Himalayan Region and the adjoining plains of northwest India during the next five days.
Under the influence of lower level wind convergence and monsoonal easterly and south-easterly wind, fairly widespread rainfall is very likely to occur over Odisha, West Bengal, Sikkim, Jharkhand, Chhattisgarh and Bihar during the next five days.
Chhattisgarh and Jharkhand will experience isolated heavy rainfall between June 22 and 23. The Sub Himalayan, West Bengal and Sikkim will have rainfall between June 22 and 25.
Due to the strengthening of moist south-westerly winds, Northeast India is likely to experience fairly widespread rainfall during the next seven days.
Subdued rainfall activity is likely over west-central and southern parts of India during the next week.