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How was the forecasting of the cyclone aila was done by the metrological department?
Cyclone Aila (also known as Severe Cyclonic Storm Aila) was the second tropical cyclone of the 2009 North Indian Ocean cyclone season. A relatively strong tropical cyclone, it caused extensive damage in India and Bangladesh. India Meteorological Department (IMD) Cyclone Warning Services
The cyclone warning organization of IMD has a three tier system to cater to the needs of the maritime States. These are : Cyclone Warning Division set up at IMD Head Quarters New Delhi 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 Centers at Visakhapatnam, Ahmedabad and Bhubaneswar. The cyclone warning services is also coordinated with the Forecasting Division at Pune.

Monitoring of Cyclones by IMD
IMD has a well-established and time-tested organization for monitoring and forecasting tropical cyclones. A good network of meteorological observatories (both surface and upper air) is operated by IMD, covering the entire coastline and islands. The conventional observations are supplemented by observational data from automatic weather stations (AWS), radar and satellite systems. The satellite techniques (INSAT imagery obtained at hourly interval) are now used to find out the centre and intensity of the system. It is also used to find out various derived parameters which are useful in monitoring the development and movement of cyclones. The radar can be utilized to find out the location of the cyclonic storm more accurately when the system comes within radar range (approx. 400km). In addition it can find out convective cloud cluster, wind distribution, rainfall rate etc.

How track prediction is done in IMD
Tropical Cyclones move as a whole. The average speed is 15-20 kmph (360-480 km/day). They may change their direction of movement. When the speed of movement is 10-14 kmph, it is called as slow moving cyclone. If the speed of movement is more than 25 kmph, is called as fast moving cyclone. 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
    VAnalogue Techniques
    Numerical weather prediction models

 Nomenclature of Tropical Cyclone
Tropical cyclones are named to provide easy communication between forecasters and the general public regarding forecasts, watches, and warnings. Since the storms can often last a week or longer and that more than one can be occurring in the same basin at the same time, names can reduce the confusion about what storm is being described. The Southwest Indian Ocean tropical cyclones were first named during the 1960/1961 season.

Intensity Prediction
Subjective techniques like Climatology, Synoptic and Satellite (Dvorak) techniques and radar techniques are used for predicting intensity. Though the performance of Numerical Weather Prediction models in intensity prediction is not satisfactory, they provide valuable guidance in intensity prediction also.

4-stage warning system for Tropical Cyclones-
Since pre-monsoon cyclone season of 1999, IMD has introduced a 4-Stage warning system to issue cyclone warnings. They are as follows:

    Pre-Cyclone Watch
    Issued when a depression forms over the Bay of Bengal irrespective of its distance from the coast and is likely to affect Indian coast in future. The pre-cyclone watch is issued by the name of Director General of Meteorology and is issued at least 72 hours in advance of the commencement of adverse weather. It is issued at least once a day.
    Cyclone Alert
    Issued at least 48 hours before the commencement of the bad weather when the cyclone is located beyond 500 Km from the coast.
    Cyclone Warning
    Issued at least 24 hours before the commencement of the bad weather when the cyclone is located within 500 Km from the coast. Information about time /place of landfall are indicated in the bulletin. Confidence in estimation increases as the cyclone comes closer to the coast.
    Post landfall outlook
    It is issued 12 hours before the cyclone landfall, when the cyclone is located within 200 Km from the coast. More accurate & specific information about time /place of landfall and associated bad weather indicated in the bulletin. In addition, the interior distraction is likely to be affected due to the cyclone are warned in this bulletin.


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