Weather forecasting · GS-I
Rain eases over Keralam as cyclone makes landfall; mercury set to climb ↗
Consider the following statements regarding the tropical cyclone life cycle and associated weather phenomena over the Indian subcontinent:
- A cyclonic storm that makes landfall typically weakens progressively, first into a deep depression and then into a low-pressure area, as it moves inland and is cut off from the warm ocean surface that sustains it.
- An upper-air cyclonic circulation over the Bay of Bengal or Andaman Sea is itself classified as a named cyclonic storm by the India Meteorological Department, and its future track can be forecast with high precision at the time of its detection.
- The northeast monsoon predominantly influences rainfall over peninsular India, particularly the southeastern coast, during the October–December period, and a Bay of Bengal low-pressure system during this season can help bridge rainfall deficiencies in states such as Kerala.
Which of the statements given above is/are correct?
Explanation
Statement 1 is correct. When a tropical cyclone makes landfall, it is cut off from the warm ocean waters that supply heat and moisture to sustain it. As a result, it weakens in stages — from a cyclonic storm to a deep depression and eventually to a low-pressure area or remnant circulation. This staged weakening is a well-established feature of the tropical cyclone life cycle, consistently reflected in IMD forecasting bulletins. Statement 2 is incorrect on two counts. An upper-air cyclonic circulation is a precursor weather feature, not a named cyclonic storm. IMD classifies and names a system as a cyclonic storm only after it reaches a defined wind-speed threshold. Moreover, at the stage of an upper-air circulation or nascent low-pressure area, the future track and intensity are inherently uncertain, and IMD typically cautions that it is 'too early to forecast' the system's influence on specific regions — which is precisely the caveat issued in operational forecasts for such developing systems. Statement 3 is correct. The northeast monsoon (also called the retreating monsoon) is the primary rainfall mechanism for peninsular India — especially Tamil Nadu, coastal Andhra Pradesh, and to a lesser extent Kerala — between October and December. During this season, low-pressure systems that develop over the Bay of Bengal track westward or northwestward and can bring significant rainfall to these states, helping to compensate for any deficiency accumulated during the southwest monsoon.