Date of Analysis: October 3, 2025 (Based on the individual weather assessment by MAS Rainman Venkatesh).
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Introduction and Disclaimer
We bring you the latest analysis of the weather systems currently affecting South India and an important preview of the upcoming Northeast Monsoon (NEM). Please note that this is a personal weather assessment (தனிப்பட்ட வாநிலை அனுமானம்). For all official weather advisories and information, please adhere to the announcements made by the India Meteorological Department and governmental sources.
Current Status of Major Weather Systems
The weather picture is dominated by two key systems:
1. Bay of Bengal System: The Deep Depression that formed in the Bay of Bengal yesterday has moved and weakened. It successfully crossed near Gopalpur in Odisha. Currently, it has weakened into a well-marked low-pressure area (வெல் மார்க்ட் லோ பிரஷர்) situated over Southern Odisha and the regions bordering Jharkhand and Chhattisgarh. This system is forecast to move first west-northwest, then west, passing between Uttar Pradesh and Bihar, and eventually reaching the Himalayan regions within the next 48 hours.
2. Arabian Sea System: A separate deep low-pressure area currently near the Gujarat coast is predicted to strengthen today into a Deep Depression (தீவிர ஆழ்ந்த தாழ்வு). This system is notably stationary (எங்குமே நகராம) in the Arabian Sea, near the Gujarat coastal areas. It is expected to track along the axis of the westerly trough for the next 24 hours. However, it is forecast to lose strength and become inactive within the next four days.
Shift in Rainfall: Intensification of Convectional Rain (வெப்பச்சலன மழை)
The presence of the stationary system in the Arabian Sea is creating a hindrance (தடை) to the required inflow of the Southwest Monsoon winds. As a result, the Southwest Monsoon rainfall is currently experiencing a slump (தொய்வு நிலையில் இருக்கு) in the West Coast areas.
This shift in wind dynamics, combined with the passage of a trough system, is triggering the intensification of convectional rain (வெப்பச்சலன மழை). This type of rain began yesterday in the northern districts of Tamil Nadu and is expected to intensify starting today. This convectional activity will spread to both the Northern and Southern districts of the state.
Detailed 24-Hour Rainfall Forecast
Rainfall activity is expected across multiple South Indian states:
Kerala
• Moderate to Heavy Rain: Expected in Idukki, western parts of Pathanamthitta, Ernakulam, Thrissur, Malappuram, Kozhikode, Kannur, and Kasaragod districts.
• Light Rain: Expected in most parts of Wayanad, Palakkad, Kottayam, Alappuzha, Pathanamthitta, Kollam, and Thiruvananthapuram.
• The rain in Kerala is likely to manifest as thunderstorm activity (தண்டர்ஸ்டாம் ஆக்டிவிட்டியாகவே), often referred to as 'convictional rain'.
Karnataka
• Moderate to Heavy Rain: Expected in Bengaluru and its surrounding areas, Kolar, KGF, Ramnagara, Chamarajanagar, Mandya, Tumakuru, Hassan, Kodagu, and Davanagere.
• Light Rain: Expected in most other districts.
Andhra Pradesh (AP)
• Rayalaseema: Moderate to heavy rain is anticipated, specifically affecting Chittoor, Tirupati, Kadapa, Nandyal, Anantapur, and Satya Sai districts.
• North AP: Moderate to heavy rain is possible in districts including Srikakulam, Visakhapatnam, Vizianagaram, Anakapalli, Kakinada, and Alluri Sitharama.
Telangana
• Western & Northwestern Districts: Moderate to heavy rain is expected in some parts, including Adilabad, Komaram Bheem, Mancherial, Jagtial, Peddapalli, Karimnagar, Jayashankar, Warangal, Mulugu, Mahabubabad, and Kothagudem.
• Light Rain: Expected in scattered areas of Hyderabad and other districts.
Tamil Nadu (TN)
Rain is expected to be widespread across Tamil Nadu today, similar to yesterday.
Region | Districts Affected | Rainfall Intensity | Notes |
South TN | Nagercoil, Kanyakumari, Tirunelveli, Tenkasi, Virudhunagar, Ramanathapuram | Light rain (some parts) to Moderate rain (few parts) | |
Central/Delta | Theni, Dindigul (town and eastern parts), Madurai, Sivaganga, Pudukkottai, Ariyalur, Thanjavur, Nagapattinam, Mayiladuthurai, Thiruvarur | Moderate to Heavy rain | |
North/West TN | Nilgiris, Erode, Krishnagiri, Dharmapuri, Salem, Namakkal, Chennai, Tiruvallur, Kanchipuram, Chengalpattu, Ranipet, Vellore, Tiruvannamalai, Kallakurichi, Cuddalore, Puducherry, Villupuram | Widespread Moderate to Heavy Rain | Heavy rain potential in coastal Cuddalore, Chengalpattu, Villupuram, Kallakurichi, and Tiruvannamalai. |
Northeast Monsoon (NEM) Preliminary Update
The outlook for the upcoming Northeast Monsoon season suggests significant weather changes are imminent:
The Critical Wind Shift
The current wind pattern, which shifts between west/southwest and east/northeast/southeast directions, is expected to fully change direction within the next Five to Eight days. The wind is anticipated to fully shift to the easterly direction.
Initial Heavy Rain Episodes
During this transition period (the next few days), there is a possibility of heavy rainfall (கன மழைக்கான வாய்ப்புகள்) in most parts of Tamil Nadu, Rayalaseema, South Interior Karnataka, and Kerala.
NEM Timeline and Onset Indicators
1. System Formation (Oct 12-15): Weather models suggest two potential systems: a circulation forming in the Southern Andaman regions around October 14 or 15, and an upper-air cyclonic circulation forming in the Gulf of Mannar region between October 12 and 14.
2. Initial Easterly Rain (South & Delta): The easterly winds will fully settle in the Southern Tamil Nadu and Delta regions first, starting around October 12-13. Rain from the east is expected to begin in these regions on the 12th, 13th, and 14th.
3. Initial Easterly Rain (North Coast): For the Northern Coastal districts, stretching from Chennai up to the Andhra regions, the easterly rain systems are expected to commence from the night of the 14th or the 15th of October.
4. Major Heavy Rain Episode: A significant episode of heavy rain (ஒரு பெரிய கனமழைக்கான எபிசோடு) is anticipated between October 10 and October 14/15 across South Tamil Nadu, the North Delta, and the Western districts. Moderate to heavy rain will also continue in the Northern interior districts.
5. Chennai Coastal Rain: Rain from the incoming easterly winds is expected to begin in the Chennai coastal districts around the 17th of October. Interior and suburban areas of Chennai may see higher rainfall accumulation during this time.
6. Full NEM Onset: The complete onset of the Northeast Monsoon (வடகிழக்கு பருவமலை தொடக்கம்) is projected to occur between October 18 and 22.
7.NEM (North East Monsoon) Inference will be released around second week of October.
Stay updated !!!
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