BoB System Dissipates Over UP After Bringing Heavy Rain Across India; Drier Weather Ahead
Key Takeaways:
- The Bay of Bengal system has lost its organised surface circulation over Uttar Pradesh, though an upper-air cyclonic circulation persists.
- The system travelled from the North Andaman Sea across Andhra Pradesh, Odisha, Chhattisgarh, Madhya Pradesh and Uttar Pradesh.
- Heavy rain, flooding, waterlogging and agricultural impacts were reported across several states along its track.
- Drier weather is expected across much of North and Central India, potentially allowing southwest monsoon withdrawal to resume.
- Forecast Validity: Next 24–48 hours.
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The long-lived weather system that began over the Andaman Sea and crossed India has lost its identifiable surface circulation. An upper-air cyclonic circulation, nevertheless, remains over East Uttar Pradesh between approximately 1.5 and 3.1 km above mean sea level.
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A Long Journey Across India
The system first formed as a low-pressure area over the North Andaman Sea before moving west-northwestwards across the Bay of Bengal.
It intensified into a depression and subsequently a deep depression before crossing the North Andhra Pradesh coast, southwest of Kalingapatnam, around midnight on 23-24 September.
After crossing land, the system moved through northern Andhra Pradesh, southern Odisha, Chhattisgarh and eastern Madhya Pradesh. It retained depression strength unusually far inland before reaching Southeast Uttar Pradesh.
On 27 September, it weakened into a well-marked low over northern parts of central Uttar Pradesh. The disappearance of the surface low on Monday marks the end of its organised synoptic life cycle.
Why Clouds Can Persist
A low “becoming less marked” means that forecasters can no longer identify a sufficiently organised closed-pressure feature at the surface.
This does not mean that all cloud and rain activity will end instantly. The upper-air circulation is still present and can support isolated showers or thunderstorms where adequate moisture and local wind convergence remain available.
A western disturbance is also present as an upper-level cyclonic circulation over North Pakistan and adjoining Jammu. Its separation from the weakening tropical circulation should gradually reduce the large-scale interaction that caused heavy rain over Uttar Pradesh and the western Himalayas.
Major Impacts Along the Track
The system produced an exceptional multi-state rainfall episode. Coastal Andhra Pradesh received extreme rain during the crossing, followed by extraordinary totals across southern Odisha and Bastar.
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It subsequently carried heavy rain into Madhya Pradesh, Uttar Pradesh and the Himalayan foothills. The most serious wind hazard occurred near the Andhra coast, but flooding, waterlogging, lightning and crop damage extended much farther inland.
The circulation affected paddy, maize, pulses, cotton, soybean, sugarcane and vegetable-growing regions. Recovery may take longer where fields remain saturated or rural roads have been damaged.
Quieter Weather Ahead
No heavy-rain warning is currently listed for East or West Uttar Pradesh from 28 September. A broadly drier pattern is expected over much of northern and central India as the remnant circulation weakens.
Local thunderstorms can still occur, but they should no longer be described as impacts from an active depression.
The system’s dissipation may also allow the southwest monsoon withdrawal process to resume over other eligible parts of India. That remains a forecast possibility rather than an official declaration, as the withdrawal line had not changed by Monday morning.
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