Southwest Monsoon Onset Likely Today: Progress May Be Slow
Key Takeaways:
- Southwest Monsoon is likely to make onset over Kerala today.
- Rainfall has already intensified across coastal and interior Kerala.
- Strong monsoon westerlies and cross-equatorial flow are supporting the onset conditions.
- Further advancement of monsoon across South India may remain slow initially.
Southwest monsoon is likely to set in over mainland Kerala today. It has rained well for the past two days all along the coastline of the state and interiors as well. Though the monsoon may not start with a bang, yet the basic conditions are likely to be met and facilitate the announcement of onset. Further progress may remain slow and sluggish over southern parts.
Normally, within about five days after the onset over mainland Kerala, the stream covers the entire state of Kerala, Tamil Nadu, Coastal Karnataka and reaches Goa along the Western Coast. The monsoon winds run across most parts of Karnataka, half of Andhra Pradesh and complete Northeast India during this period.
Prior to the arrival of monsoon, a set of conditions need to get aligned for the declaration of the much-awaited event. These conditions include rainfall, cloud cover and the seasonal westerly winds. Most important among these are the streaming monsoon westerly winds, which need to have adequate speed and sufficient depth over a specified area in the Arabian Sea and equatorial Indian Ocean. Though the visible manifestation of arrival is through rainfall, both along and off the coast of Kerala, Lakshadweep region and Coastal Karnataka, the prevalence of westerly winds scores over all other conditions.
At times, the pre-monsoon showers over the state may sound similar to the monsoon current and therefore, the monsoon westerly winds are more authentic to justify the landing of monsoon. The westerly winds need to be strong over the sea and supported by healthy cross-equatorial flow. Also, these winds need to have sufficient depth, preferably up to 12,000 feet above sea level.
During the last two years, in 2024 and 2025, the monsoon had arrived a little earlier than the stipulated date of 01st June. The onset date has a standard deviation of one week. Therefore, even the onset on 04th June will be considered timely. The seasonal rainfall count starts from 01st June, irrespective of the arrival date of monsoon. For the first three days, the monsoon rainfall is short by 29% between 01st and 03rd June 2026.
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