Weather Watch: Low Pressure Forms, Analyzing the Road to a Grand Northeast Monsoon Start! - As per Weekly Anomaly Update from ECMWF
Welcome back! This is your analysis of current weather systems and a deep dive into the long-range forecast stretching up to early November. Please note: This is an independent weather estimation. For official alerts and information, please follow the India Meteorological Department and government announcements.
The Current Setup: LPA Forms Amidst a Distant Storm
A crucial development is underway in the Bay of Bengal: the circulation between Odisha and West Bengal has strengthened into a Low-Pressure Area (LPA). We anticipate that over the next 24 hours, this LPA will move closer to Odisha, sink back into the Bay, and further intensify into a Depression (ஆழ்ந்த தாழ்வு பகுதி).
However, the strengthening process is currently seeing a slight delay. This is due to a powerful, distant storm: Typhoon Ragasa, a Category 5 super cyclone, is currently active in the South China Sea, boasting an extremely low central pressure of 930 mb. Moisture and energy from Central India, passing over the Bay of Bengal, are currently feeding this powerful Typhoon. It is only after this Typhoon makes landfall in the South China Sea region (expected within the next 24 hours) that the LPA near Odisha will begin to truly gain strength.
Meanwhile, the Southwest Monsoon is continuing its withdrawal process, having already retreated from Gujarat, Himachal Pradesh, Punjab, and Haryana.
Immediate Rainfall Impacts (Next 24-48 Hours)
As the LPA strengthens into a Depression between Odisha and Visakhapatnam, it is expected to travel inland through Telangana at a low latitude.
• West Coast: The strengthening of the Southwest Monsoon winds along the Western coast will lead to a gradual increase in rainfall intensity starting today. Regions like Maharashtra, Goa, Konkan, Kerala, Karnataka (both coastal and interior) are set to receive rain.
• Andhra & Telangana: Rainfall intensity is expected to increase here as the system strengthens.
• Tamil Nadu (TN): For the immediate future, widespread rainfall is expected to be low. TN will primarily experience isolated instances of convective rain (வெப்பச்சலன மழை).
Today's Rain Prospects (Next 24 Hours)
Kerala is predicted to see widespread moderate to heavy rain across many districts, including Thiruvananthapuram, Kollam, Idukki, and Thrissur. Karnataka forecasts include heavy rain for districts in Kalyan Karnataka (Bidar, Gulbarga), Coastal Karnataka (Mangaluru), and cities like Bengaluru.
For Tamil Nadu, moderate to heavy rain is likely in the following areas today:
• The Nilgiris district.
• The Pollachi and Valparai/Sholayar regions.
• The Western Ghats areas near Tenkasi (Kutralam), Tirunelveli (Oothu), and Kanniyakumari.
• North Interior and Coastal districts, including Krishnagiri, Tirupattur, Villupuram, Puducherry, Cuddalore, Kanchipuram, Chengalpattu, Chennai, and Tiruvallur.
• Most other TN districts are likely to experience widespread cloud cover with only light rainfall.
The Long View: Analyzing the Northeast Monsoon (NEM) Timeline
By analyzing weekly weather anomalies (where green/dark green indicates above-normal rain and orange indicates below-normal rain), we can map the transition towards the Northeast Monsoon:
1. September 23 – 29: Rainfall Surge in the Deccan and West Coast
Central India, Andhra Pradesh, Odisha, Telangana, Maharashtra, Chhattisgarh, Jharkhand, Karnataka, and Kerala are expected to receive above-normal rainfall during this period. Tamil Nadu's central and western regions anticipate normal rainfall, while North Coastal districts (including Chennai, Kanchipuram, and Puducherry) may see slightly above-normal rain.
2. September 29 – October 6: A Dip in TN Rain
The Depression moves across Maharashtra and into the Arabian Sea, and a new circulation forms near Odisha. During this time, Central/North India, Maharashtra, Gujarat, Rajasthan, and Coastal Karnataka will experience above-normal rain. However, most districts in Tamil Nadu are forecasted to see below-normal rainfall. Only Northern Coastal areas (from Vellore to Puducherry) are likely to see normal rainfall.
3. October 6 – October 13: The Wind Transition
This phase is critical as the westerly winds begin shifting to easterly winds—a preliminary sign leading up to the NEM. Above-normal rain continues across parts of North and Central India (UP, Delhi, Bihar, MP, Gujarat, Odisha). TN is expected to receive normal rainfall, while Kerala and Karnataka may see below-normal rainfall.
4. October 13 – October 20: Eastern Winds Arrive
This is a key development: Easterly winds will fully arrive in Tamil Nadu after October 13. Most areas of TN will begin to receive above-normal rainfall. The possibility of the Northeast Monsoon starting is evident during this timeframe.
5. October 20 – October 27: NEM Onset Likely
This period strongly suggests the Northeast Monsoon will begin. A trough structure is expected near Sri Lanka. There is potential for a "Grand Onset" this year. Coastal areas from Chennai down to the Delta districts, as well as Southern districts (e.g., Ramanathapuram, Kanniyakumari), are forecast to receive double the normal rainfall. Interior and Western districts are also expected to receive good, above-normal rain.
6. October 27 – November 3: Peak Rain Expected
A prolonged period of rain is forecast, with a circulation expected to persist in both the Bay of Bengal and the Arabian Sea. This setup will generate a strong, moist easterly wind flow. Coastal Tamil Nadu has a high chance of heavy rain. Specifically, North Coastal districts (Chennai, Tiruvallur, Kanchipuram down to Puducherry) are highlighted for the possibility of very heavy rainfall.
This forecast suggests the Northeast Monsoon will have a great start this year, potentially bringing rain around the time of the Deepavali festival.
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