Detailed Weather Update: Upper Air Circulation Forms Near Kanyakumari, Bringing Heavy Showers to South India (October 9, 2025)
Good morning! Today, October 9, 2025, we are tracking significant weather changes that will bring widespread rainfall across South India.
(Note: This is a personal weather analysis and forecast. For official weather bulletins and information, please follow the announcements from the Indian Meteorological Department and RS SR).
The Main System: Upper Air Cyclonic Circulation (UAC)
The most important system driving the current weather is a Upper Air Cyclonic Circulation (வளிமண்டல மேலெடுக்கு சுழற்சி). This system formed last night and continues to persist, stretching from the Kanyakumari and Gulf of Mannar regions towards the adjacent Arabian Sea. This UACC is poised to be a significant factor—a "hero"—in the weather patterns over the coming days.
This UACC is primarily responsible for triggering pre-monsoon convective showers (வெப்பச்சலன மழை) across a large area, including Tamil Nadu, Andhra Pradesh, Karnataka, and Kerala, before the official commencement of the Northeast Monsoon.
Current Atmospheric Conditions
Several key atmospheric changes are occurring simultaneously:
- SW Monsoon Withdrawal: The Southwest Monsoon has fully withdrawn from Northern India. It is expected to withdraw from most central and northern Indian regions today or tomorrow.
- Weakened Cyclone: The powerful Shakti Cyclone in the Arabian Sea has completely dissipated, weakening into a low-pressure area.
- Atmospheric Instability: South Indian regions, particularly interior Karnataka, Andhra Pradesh, Tamil Nadu, and Kerala, are experiencing significant atmospheric instability (காற்றின் நிச்சயமற்ற தன்மை). The "wind shear" (காற்றின் முறிவு) in these regions is strong. This configuration typically occurs just before the wind direction shifts.
Detailed Rainfall Forecast for the Next 24 Hours
Widespread moderate to heavy rain is expected in many areas today. In many parts of Tamil Nadu, rainfall is anticipated to begin around 10 or 11 am.
The moisture dynamic involves sea breeze (கடல் காற்று) coming from the east, causing light to moderate rain along the coastal districts. However, as this "remnant moisture" moves inland (மாய்ஸ்சர் மூவிங்), it encounters the areas of atmospheric shear (காற்றின் முறிவு), creating favorable conditions for rain clouds—a characteristic of these transition period rains.
Tamil Nadu
Areas Expected to Receive Moderate to Heavy Rain:
- South Tamil Nadu: Nagercoil, Kanyakumari, Tirunelveli, Virudhunagar, Theni, Dindigul, Madurai, Sivaganga, and Pudukkottai districts.
- Western & Interior Districts: Nilgiris, Coimbatore, Tiruppur, and Erode.
- Northern & Interior Districts: Salem, Namakkal, Krishnagiri, and Dharmapuri.
- North TN Plains: Widespread moderate to heavy rain is expected, potentially with thunderstorms (இடிமுன்னலுடன்), in Vellore, Tiruvannamalai, Kallakurichi, Karur, Namakkal, Trichy, Perambalur, Ariyalur, western Cuddalore, Tiruvallur, Ranipet, Kanchipuram, Chengalpattu, and Villupuram. Residents in these areas should exercise caution (சற்று ஜாகிரதையாக இருக்க வேண்டும்).
Areas Expected to Receive Heavy to Very Heavy Rain (Isolated):
- Pockets near the Western Ghats in Theni district, Valparai, Solaiyar, and Pollachi.
- Isolated parts of Erode/Namakkal, specifically the Sathyamangalam region.
- Isolated locations within Krishnagiri district and Tirupattur district.
Areas Expected to Receive Light to Moderate Rain (Coastal):
- Coastal districts including Chennai, Tiruvallur, Chengalpattu, Pondicherry, Cuddalore, Mayiladuthurai, Nagapattinam, Karaikal, Tiruvarur, eastern Pudukkottai, eastern Sivaganga, Ramanathapuram, Thoothukudi, and Tenkasi.
Kerala
Kerala expects moderate to heavy rain across several districts:
- Western Regions: Moderate to heavy rain, potentially strong in some areas, is forecasted for Thiruvananthapuram, Kollam, Pathanamthitta, Kottayam, Idukki, Ernakulam, and Thrissur.
- Northern Regions: Widespread moderate to heavy rain is also likely in Malappuram, Wayanad, Kannur, and Kasaragod districts.
Karnataka
Heavy rain is anticipated in most interior regions of Karnataka.
- Heavy/Intense Rain Focus: Heavy rain, and potentially intense rain, is expected in KGF, Kolar, Chikkaballapur, Bengaluru, and Ramanagara districts. Similar intensity is expected in Mysore, interior areas like Hassan, Chitradurga, western Tumkur, and Chikmagalur.
- Widespread Moderate to Heavy Rain: Rain is likely in Belgaum, Uttara Kannada, Dharwad, Gadag, Koppal, Bellary, Vijayanagara, Haveri, Shimoga, Udupi, Dakshina Kannada, Kodagu, Hassan, Mandya, Chamarajanagar, and Tumkur.
- Lower Chances: The Kalyan Karnataka region generally has low chances of rain.
Andhra Pradesh & Telangana
- Andhra Pradesh: Widespread convective rain is expected today. Heavy to intense rain is possible in Anantapur, Tirupati, and Chittoor districts.
- Telangana: Rainfall has significantly reduced. Only moderate to heavy rain is expected in Mahabubabad, Kothagudem, Mulugu, and Khammam districts; rainfall chances are low in other areas, including Hyderabad.
The systems currently observed continue to suggest favorable conditions for the Northeast Monsoon (வடகிழக்கு பருவமழை). It is highly likely to begin around its normal date, which is currently anticipated to be October 17 or 18.
A full preview and comprehensive update regarding the Northeast Monsoon's structure and progression will be released in a dedicated video tomorrow evening.
Stay Tuned for More Updates: !!!
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