Skymet weather

Why Monsoon Has Become 'Doldrums': August May Be Driest In Over 100 Years

August 21, 2023 2:12 PM |

Month of July boosted monsoon outlook 2023 with 13% surplus rainfall.  Soaking month also covered 10% rainfall deficiency of June and raised the long period average (LPA) to above normal at 105%, half way through the season. Most weather services and few individual ‘bloggers’ discarded evolving El Nino conditions and announced safe passage to the southwest monsoon 2023.  Typical ‘Evolving El Nino’ strikes hard in the 2nd half of the season, as is being witnessed now. Skymet had cautioned in its comprehensive monsoon forecast released on 10thApril 2023 about aberration of monsoon rainfall during 2nd half of the season.

El Nino does not spare the Indian monsoon very often. Last it remained soft on monsoon was 1997 when the country recorded a normal monsoon with seasonal rainfall of 102% of LPA.  Thereafter, 2002, 2004, 2009, 2014, 2015 suffered drought with 2002 and 2009 recording severe drought.  Season 2018 narrowly escaped drought and monsoon ended with a deficit of 9.4 %. Any deficiency, above 10% lists the monsoon as a ‘drought’ year.

Sufficient warming of central and eastern Pacific Ocean lasting for longer duration is termed as El Nino. El Nino is the most chaotic climate fluctuation affecting globally at different times, in general, and Indian sub-continent during southwest monsoon from June to September.  Evolving El Nino has a lag in its evolution and impact, as volume of water is always slow to absorb heat.

El Nino derailed the monsoon track in August, by going in to a long ‘break’ for nearly 2 weeks.  Though, monsoon break is very common in August, specially after an active spell for couple of weeks in July.  It is part of intra-seasonal variation of the monsoon characteristics. However, most ‘breaks’ last for about a week or less. Any prolonged slumber is attributable to the El Nino.  Longer than normal ‘break’, as usual, shifted the monsoon trough closer to the foothills of Himalayas. In such situations, rainfall activity gets limited to foothills of Indo-Gangetic plains, stretching from Punjab to Bihar, Sikkim, Sub Himalayan West Bengal and Northeast India.

Revival from the ‘break’ invariably commences with the formation of monsoon system over Bay of Bengal (BoB).  Monsoon low pressure did form over BoB, but the powerful El Nino did not allow a proper revival. Monsoon low pressure followed indifferent track and also did not penetrate deep in to western and northern parts of the country. Accentuation of rainfall for merely 2 days was not adequate enough to break the jinx of weak phase of monsoon.  This low pressure area which formed on 18thAug 2023 had travelled across Odisha, Chhattisgarh and Madhya Pradesh. The system has become less marked now and is likely to merge with the monsoon trough shortly. The monsoon trough, which temporarily shifted southward, will again get relocated to the foothills. Active rainfall belt will shift again to the northern parts of Indi-Gangetic plains, akin to another ‘break’ in the monsoon.

El Nino had increased the frequency and intensity of typhoons in the Western Pacific. Severe Tropical Storms namely Dodong, Doksuri, Khanun, Lan and Dora struck the Pacific ring countries and trampled the Philippines, China, Taiwan, Japan and South Korea during July and till the middle of August.  Dora was the only typhoon crossing International Date Line, during its travel over open seas. Though these storms appear to be sailing at a safe distance from the Indian region, these monsters sap the monsoon stream of moisture, much need for active monsoon conditions. These typhoons influence the wind pattern to thousands of kilometres and suppress the revival of monsoon and restrict the relocation of seasonal monsoon troughs to their normal position.

The El Nino basin in the central and eastern Pacific Ocean is too warm and is churning numerous storms and hurricanes. Currently, there are 4 strong tropical storms ( Hilary, Franklin, Gert, Emily)  and 2 potential storms as ‘Invest Area’ in close proximity over Equatorial Pacific and North Equatorial Atlantic. This proves the power of El Nino disrupting weather over  large pockets around the globe.

For the Indian monsoon, the month of August has gone on record to have rainfall deficiency in excess of 35%, the highest ever in the last more than 100 years. There are still 10 days to go but any major recovery is unlikely. The month of August recorded a large deficit of 24% (2005), 26% (2009), 23% (2015) and 24% (2021). Prior to this, a deficiency of 31% ( only deficit year with a shortfall of > 30% in over 100 years) was recorded in 1913. In between, 1920 also recorded a shortfall of 28% in the month of August. The highest-ever shortfall of 40% rainfall was recorded in August 1899.  August 2023 may fall short of breaching this record but still score as the  ‘most deficit’  in the last over 100 years.

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