Cyclone forecasting and Warning by IMD


Ajit Kumar AJIT KUMARWISDOM IAS, New Delhi.


The cyclone tracking, forecasting and advance warning are being done by India Meteorological Department (IMD) precisely after the Meteorological application program of INSAT series of Indian Geo-Stationary Satellites  have become operational since October 1983. Monitoring of the cyclone by taking hourly pictures has helped the forecaster to improve his skill in issuing the timely warnings to the public. Satellite pictures received by the IMD HQ at New Delhi are further disseminated to all the forecasting Offices through satellite based Digital Meteorological Data Dissemination Systems.  The Government has strengthened the Meteorological Department, by providing Cyclone Surveillance Radars at Calcutta, Paradeep, Visakhapatnam, Machilipatnam, Chennai and Karaikal in the east coast and at Kochi, Goa, Mumbai and Bhuj in the west coast for further cyclone warning when they are within a close approach of 500 km off  coast.



Techinques


Various Techniques are available for Track Prediction of the storm as mentioned below:
Methods based on climatology, persistence and both Climatology & Persistence (CLIPER)
Synoptic Techniques – Empirical Techniques
Satellite Techniques
Statistical Techniques using climatology, persistence and synoptic
Analogue Techniques
Numerical weather prediction models
Warning Centres 
Area Cyclone Warning Centres (ACWC) and the Cyclone Warning Centres (CWC) of IMD  are responsible for cyclone forecasting in the Bay of Bengal and  Arabian Sea - the National Cyclone Warning Centre at New Delhi being the coordinator. Computerised Operational Advisory Forecasts on cyclone movements are being issued by the Numerical Weather Prediction (NWP) division of the Department at the H.Q., New Delhi  
Four Stage Warning
ACWC  issues four stage warnings on Cyclone alert & Cyclone warning, in case of a system striking the coast or near the coast and  port & fisheries warnings and heavy rainfall warnings for various agencies.    After receipt of pre-cyclone watch bulletin issued by HQ, ACWC/CWC will monitor issue of warnings under two stage warning system- Cyclone Alert and Cyclone Warning.
 Cyclone Alert,  the first stage warning: This is issued 48 hrs. in advance of the commencement of adverse weather, to Collector of coastal districts and the Chief Secretary of the concerned maritime state.  After issue of alert message for broadcast, the concerned AIRs are to be requested to maintain round the clock watch to receive & broadcast the subsequent numbered bulletins.
 Cyclone warning – the second stage warning:  This is issued 24 hrs. in advance of the commencement of adverse weather.  Subsequent to this warning, any other crucial warning is being sent more frequently to all the concerned recipients (Collectors & Chief Secretaries), if the storm is tracked by radar with a high degree of confidence.    These recipients will be informed that subsequent warning on the storm will be broadcast by AIR stations. 
The fourth stage of the warning, ie. Post Landfall Outlook (PLO) meant for Interior districts issued 12 hrs. before the estimated landfall of the storm in order to bring to the notice of the Collectors of interior districts about their area likely to be affected by cyclone. 
Intensity Prediction
Subjective techniques like Climatology, Synoptic and Satellite (Dvorak) techniques and radar techniques are used. Though the performance of NWP models in intensity prediction is not satisfactory, they provide valuable guidance in intensity prediction also.
 Cyclone Warning Dissemination System
One of the means of communication, on which IMD depends for the dissemination of these warnings, other than AIR, is satellite based Cyclone Warning Dissemination System (CWDS) installed at maritime district HQ, so that district authorities can initiate appropriate precautionary measures on receipt of such warnings.  This scheme makes use of the S-band broadcast capability of INSAT satellite.   At present there are 5 CWDS stations located in Kerala, which are  at Thiruvananthapuram, Alappuzha, Ernakulam , Thrissur and Kozhikode . 


Organizational set up in IMD


The Cyclone Warning Organization in India has a 3-tier system to cater to the needs of the maritime States. These are : Cyclone Warning Division set up at IMD Head Quarters to co-ordinate and supervise cyclone warning operations in the country and to advise the Govt. at the apex level; Area Cyclone Warning Centres at Chennai, Mumbai and Kolkata and Cyclone Warning Centres at Visakhapatnam, Ahmedabad and Bhubaneswar. The cyclone warning work is also supervised and coordinated by the Forecasting Division at Pune.


Cyclone Bulletins issued by IMD




  1. Weather and Sea area bulletins.


  2. Bulletins for Indian Navy.


  3. Bulletins for Departmental Exchange.


  4. Port Warnings


  5. Fisheries warnings


  6. Four Stage Warnings


  7. Bulletins for AIR


  8. Bulletins for Press


  9. Coastal bulletins




Saturday, 01st Feb 2014, 07:36:37 PM

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