Step 1: Cyclone-prone regions in India.
- The Bay of Bengal coast (Eastern coast: Odisha, Andhra Pradesh, Tamil Nadu) is highly prone to cyclones due to warm sea surface temperatures and favorable wind conditions. Cities like Vishakhapatnam, Paradip, and Chennai are frequently affected.
- The Arabian Sea coast (Western coast: Maharashtra, Gujarat) experiences far fewer cyclones. Cyclones form here less often and tend to be weaker compared to the Bay of Bengal cyclones.
Step 2: City-wise analysis.
- Mumbai: Located on the Arabian Sea coast, very rarely experiences cyclonic disturbances.
- Vishakhapatnam: Situated on the Bay of Bengal, cyclone-prone.
- Porbandar: Gujarat coast, occasionally faces cyclones, but more than Mumbai.
- Chennai: Tamil Nadu coast, highly prone to cyclones from Bay of Bengal.
- Paradip: Odisha coast, frequently hit by cyclones.
Step 3: Conclusion.
Among the given options, Mumbai is least likely to experience cyclonic disturbances.
\[
\boxed{\text{Mumbai is the least cyclone-prone city among the given options.}}
\]