Status and Plans for Operational Tropical Cyclone Forecasting and Warning Systems in the North Indian Ocean Region - Monitoring and Prediction of Tropical Cyclones in the Indian Ocean and Climate Change - page 146

if the wind speed is 120 knots or more (Table 1). The systems with the intensity
of depressions and above are considered as cyclonic disturbances. The 'cyclone'
is a generic term associated with a low pressure system with maximum sustained
surface wind speed of 34 knots or more (IMD, 2003).

Table 1: Classification cyclonic disturbances over the NIO

Low pressure system Maximum sustained surface winds

Low pressure area < 17 knots

Depression 17-27 kts

Deep depression 28-33 kts

Cyclonic storm 34-47 kts

Severe cyclonic storm 48-63 kts

Very severe cyclonic storm 64-119 kts

Super cyclonic storm 120 kts and above

Normally five TCs develop over the NIO including four over the Bay of
Bengal and one over the Arabian Sea. The frequency of the TCs over the NIO
accounts for about 7% of the global frequency. However, in terms of loss of
human life, the Bay of Bengal TCs have accounted for deaths ranging from a
thousand to three hundred thousand. Considering the TCs all over the globe,
which caused the human death of 5000 or more, more than 75% of such TCs
developed over the NIO during last 300 years (Dube, 2012).
Here, the current status of operational TC forecasting and warning Systems
in the NIO has been analysed and presented. Section 2 presents the broad
responsibility of IMD for TC forecasting and warning services in NIO region.
Section 3 deals with climatology, section 4 with monitoring and prediction
aspects, section 5 with warning services and section 5 with future plans for
upgradation of forecasting and warning services.

2. Broad Responsibility of IMD for TC Forecasting and
Warning Services (RSMC, 2012)

• Round-the-clock watch on weather situations over the NIO.
• Analysis and processing of global meteorological data for diagnostic and
prediction purposes.
• Detection, tracking and prediction of cyclonic disturbances in the NIO.
• Running of numerical weather prediction (NWP) models for cyclone
prediction.
• Issue of numbered Cyclone Warning Bulletins to national disaster
management agencies, other users, press/electronic media and public and
TC advisories to WMO/ESCAP Panel countries.
• Interaction with National Disaster Management Authority and National
Disaster Management, Ministry of Home Affairs, Govt. of India and other