Rainfall in Jun-Sept this year will be above normal in country except Kerala & Karnataka. IOD turning negative from July onwards may see brewing of cyclones in Bay of Bengal
SANJEEV KUMAR PATRO, ODISHA: The State is in the midst of pre-monsoon season. When the monsoon is being seen as the lifeline for Indian economy, it remains to be seen this year will it dissolve things to the bone or make them dry.
Even though the India’s top weather agency IMD is yet to come out with its Monsoon forecast, it may come in the second fortnight of April, the agency’s latest ENSO bulletin and the weather outlook by Asia Pacific Climate Centre (APCC) hint at the country witnessing a normal Monsoon this year.
While IMD says that weak La Nina conditions and neutral IOD (Indian Ocean Dipole) will prevail till June, the APCC has predicted that India will witness above normal rainfall during the period of June – September.
As per APCC, there is a 40-60 percent probability of India receiving above-normal rainfall during the period of June – Sept this year. The ace weather agency has further explained that the country will record rainfall above the mean normal rainfall computed for the 20-year period of 1991 -2010.
“Our latest ENSO outlook suggests an around 60 percent chance of La Niña conditions with weak intensity for April – June 2022, which gradually decreases. And ENSO-neutral conditions are likely to be gradually intensified and then dominant (~56%) during July – September 2022,” said APCC.
IMD Hints On Monsoon
As per the country’s premier weather forecasting agency, these are the following conditions that will drop hints about the Monsoon.
– Surface heating over South Asia reduces the near-surface stability of the atmosphere.
– Increase in south-westerlies over the Bay of Bengal.
– Rise of south easterlies in South China sea.
– Development of Somali Jet and Iranian High.
A look at the APCC data reveals that there is over 50-70 percent probability of north Indian landmass recording above normal temperature during the summer months of April-May. Similarly, the Tibetan Plateau will also be recording above normal temperature during the same period.
As per IMD report, the extreme heat conditions will release sensible heat flux leading to a large-scale reversal of the meridional temperature gradient at the surface and in the deep troposphere. As a consequence, the deep baroclinic (imbalance in the atmosphere) structure of the monsoon circulation will develop.
While the land-sea temperature contrast will lead to a shallow circulation and convection, the deep tropospheric meridional temperature gradient may lay the ground for a strong pressure gradient causing the intense low-level cross-equatorial monsoon flow and moisture transport.
The IMD’s latest ENSO forecast shows that IOD will remain neutral till June. Due to this condition, westerly winds will blow along the equator. This condition will help in the onset of monsoon in India on time.
APCC Forecast
A look at the APCC precipitation outlook shows that though monsoon will be above normal in the north, central, east and northeast India, it will be below normal in Kerala. Southern states like Kerala and Karnataka are predicted to record below normal rainfall in June-Sept period.
The probable reason behind the prediction of below-normal rainfall in the southern states like Kerala and Karnataka is attributed to negative IOD from July onwards.
Odisha Monsoon 2022
Though IMD is yet to open its cards, APCC forecast shows that Odisha will receive above-normal rainfall in June, July and September.
The deterministic forecast of APCC predicts that the State in the month of June will receive nearly 1 mm per day more than the normal mean June rainfall. It further hints at July getting bountiful rainfall for the State.
However, the month of August is predicted to record lean monsoon season for the State. Depressions will bring above-normal rainfall for the State in September, the model outlook indicates.
In sum, the State will record above-normal rainfall during the period of June – Sept this year.
2021 Flashback: Odisha had received 1060 mm rainfall between Jun – Sept 2021 (monsoon period). The normal rainfall figure had been 1158mm. As the deficit is below 20 percent, the State had been categorised as having a normal monsoon.
Though June had recorded normal rainfall, the State witnessed highly deficient July and August in 2021. Only September saw excess rainfall.
Post Monsoon And Cyclone
As per IMD study, in years when IOD has turned negative, the Bay of Bengal had seen increased instances of cyclonegenesis in the post-monsoon season. And if the historical phenomenon sets in, the states bordering the Bay of Bengal have a reason to worry.
