In Indian climatology, Kalbaisakhis or Norwesters are violent local thunderstorms that mainly originate over which of the following regions?

Introduction / Context:
Kalbaisakhis, also known as Norwesters, are famous pre monsoon thunderstorms that occur mainly in eastern India, especially over West Bengal, Bihar, Jharkhand, and adjoining areas. They bring sudden, intense showers, gusty winds, and sometimes hail, providing relief from the heat and benefiting certain crops. Many competitive exams include questions on where these storms originate and which regions they affect.

Given Data / Assumptions:

• The phenomena discussed are Kalbaisakhis or Norwesters.
• We are asked to identify the main region of their origin.
• The options include Chhota Nagpur Plateau, Karnataka Coast, Coromandel Coast, and Malwa Plateau.
• We assume the usual climatological description of these storms as found in Indian geography texts.

Concept / Approach:
Kalbaisakhis are convective thunderstorms that typically develop in the hot weather season, especially during April and May. They are associated with strong surface heating and moisture influx from the Bay of Bengal. The Chhota Nagpur Plateau and adjoining areas of Jharkhand, West Bengal, and Odisha provide ideal conditions for the uplift of warm, moist air, leading to the formation of these violent storms which then move towards the north east and east. Therefore, the key is to recall the central origin area of these Norwesters.

Step-by-Step Solution:
Step 1: Recall that Kalbaisakhis are mainly observed in parts of eastern India, such as West Bengal, Bihar, Jharkhand, and Assam. Step 2: Note that their genesis is closely linked with intense heating over the plateau region and moisture inflow from the Bay of Bengal. Step 3: The Chhota Nagpur Plateau region in Jharkhand and adjoining areas is a major heating centre that triggers these thunderstorms. Step 4: The Karnataka Coast and Coromandel Coast are coastal regions in southern India, not the core origin area for Kalbaisakhis. Step 5: The Malwa Plateau lies in central India and is not prominently associated with Norwester formation. Step 6: Hence, the primary region of origin is the Chhota Nagpur Plateau.

Verification / Alternative check:
Climatology chapters in Indian geography books describe Kalbaisakhis as pre monsoon thunderstorms that originate over the Chhota Nagpur Plateau and surrounding areas and move eastwards and north eastwards, affecting West Bengal and Assam. The storms are often shown on maps with their starting zone around this plateau. No such direct linkage is established for the Karnataka Coast, Coromandel Coast, or Malwa Plateau in standard texts, confirming that Chhota Nagpur Plateau is the correct answer.

Why Other Options Are Wrong:
Karnataka Coast: This region is associated with heavy south west monsoon rainfall and sea breeze phenomena, not specifically with Kalbaisakhis. Coromandel Coast: This south eastern coast of India is more closely linked with retreating monsoon and cyclonic storms, not with Norwesters. Malwa Plateau: Located in central India, Malwa has its own climatic characteristics but is not identified as the main origin area for Kalbaisakhis.

Common Pitfalls:
Students may confuse Kalbaisakhis with other regional wind and storm patterns, such as mango showers in Karnataka or cyclones on the Coromandel Coast. Mixing up these local weather phenomena can lead to wrong answers. To avoid this, remember a simple association: Kalbaisakhis or Norwesters are east Indian thunderstorms originating over the Chhota Nagpur Plateau region and moving towards Bengal and Assam. Keeping this mental picture will help you correctly answer related questions.

Final Answer:
Kalbaisakhis or Norwesters mainly originate over the Chhota Nagpur Plateau region in eastern India.