In the heart of New Delhi, the Indian Meteorological Department (IMD) declared that the eagerly anticipated Southwest monsoon is slated to make landfall along the Kerala coast on May 31, a day prior to its customary arrival on June 1.
Traditionally, the monsoon graces the Kerala coast around June 1, allowing for a seven-day leeway. It then spreads across the entirety of the nation in the ensuing fortnight.
Southwest Monsoon Phenomenon
According to a publication titled “Novel Standard Dates of Commencement/Advancement and Withdrawal of Southwest Monsoon across India” released by the Weather bureau in 2020, the bulk of the nation garners 70-90% of its yearly precipitation during the southwest monsoon period spanning June to September.
The publication explicates, “the inaugural monsoon showers materialize during May over the southern Andaman Sea, with subsequent northwesterly propagation of monsoon currents over the Bay of Bengal.”
It underscores that the initiation and duration of this principal rainy phase, coupled with the volume of rainfall, significantly influence “agricultural scheduling, food security, and the livelihoods of roughly 25 million robust laborers in the agrarian and affiliated domains of the nation.”
The duration of monsoon coverage extends beyond four months in numerous southern Peninsula regions, whereas it contracts by half in the northwestern sectors. The onset of the southwest monsoon across the Indian mainland is heralded by its debut in Kerala and serves as a pivotal gauge marking the transition from a sweltering, parched season to a pluvial one.
Deriving Forecast Data
For the ongoing monsoon season, the IMD’s prognostications indicate the southwest monsoon’s commencement in Kerala circa May 31, subject to a potential deviation of four days. The meteorological bureau has been dispensing operational forecasts for the onset date of the monsoon in Kerala since 2005.
An indigenous, sophisticated statistical framework, characterized by a margin of model error of ± 4 days, is employed for this purpose, as conveyed by a senior IMD functionary.
The six “Predictors” enlisted in the models encompass Minimum Temperatures across Northwestern India, Pre-monsoon precipitation peaks in the southern Peninsula, Outgoing Long wave Radiation (OLR) across the South China Sea, Lower tropospheric zonal wind patterns over the equatorial southeast Indian Ocean, OLR across the Southwest Pacific Ocean, and upper tropospheric zonal wind dynamics over the equatorial northeast Indian Ocean.
As per the meteorological authority, its forecasts concerning the onset of the monsoon have remained accurate over the past 19 years, save for an anomaly in 2015.
“IMD’s operational forecasts regarding the date of monsoon onset in Kerala over the preceding 19 years (2005-2023) were validated, barring the year 2015,” affirmed the official.
In the preceding year, the monsoon inaugurated on June 8. Contrastingly, it commenced on May 29 in 2022, June 3 in 2021, June 1 in 2020, and June 8 in 2019.
Prognostication of Heatwave Incidence in Specific States
As per the IMD’s projections, heatwave conditions are anticipated to ensue in isolated/localized regions across the Gujarat Region on May 16-17, Konkan on May 16, Saurashtra and Kutch on May 16-17, Western Rajasthan during May 16-20, Punjab, southern Haryana during May 16-19, and northern Madhya Pradesh, Eastern Rajasthan, Uttar Pradesh, Bihar during May 17-19.
Likewise, heatwave conditions are foreseen to persist in scattered regions across Delhi, Jharkhand, the Gangetic West Bengal, and Odisha during May 18-19.
The mercury in the national capital is poised to soar to 45 degrees Celsius over the ensuing weekend, as per the Meteorological department’s forecasts.
The surge in temperatures is attributed to arid westerly and northwesterly currents, in conjunction with cloudless skies facilitating direct sunlight across northern territories from Thursday onwards.
Delhi Heatwave Outlook
Elevated temperatures are expected to prevail over Delhi, Haryana, and Punjab from May 17-19, with Delhi primed to undergo its inaugural bout of severe heatwave conditions this weekend.
The National Capital is yet to register a day characterized by a heatwave, as the maximum temperature has not surpassed 4.5° C above the norm.
While Delhi and its environs are presently experiencing temperatures hovering around 40° C, projections suggest a potential escalation to 45° C come Saturday.
Prediction of Precipitation in Designated States
Isolated bouts of intense precipitation are highly probable over Tamil Nadu, Puducherry, and Karaikal, Kerala and Mahe, Coastal and South Interior Karnataka during May 16-20. Moreover, isolated instances of extremely heavy rainfall are anticipated over Tamil Nadu on May 18-19 and Kerala on May 19.
Similarly, isolated episodes of mild to moderate rainfall accompanied by thunderstorms, lightning, and gusty winds (ranging from 40-60 kmph) are expected over Konkan and Goa, Central Maharashtra, Marathwada on May 16-17, across Madhya Pradesh, Vidarbha, Chhattisgarh, Odisha, and the Gujarat Region on May 16, while isolated occurrences of hailstorm activity are forecasted in Central Maharashtra on May 16.
The meteorological office also envisages precipitation for the northeastern states encompassing Arunachal Pradesh, Assam, Meghalaya, Nagaland, Manipur, Mizoram, and Tripura during May 16-19. Furthermore, isolated spells of intense rainfall are predicted over Arunachal Pradesh during May 16-19 and Assam & Meghalaya on May 17-19.