S. M. Kulshrestha*

1. INDIA’S UNIQUE WEATHER AND CLIMATE SYSTEM

India experiences a greater variety of weather than perhaps any other region of similar size anywhere else in the world. This is so not only because of the large size of the country nor simply because India is located in the tropics although both these facts are important. Nature has bestowed upon India a unique weather and climate system that is significant from the scientific as well as socio- economic angles.

India’s unique weather and climate system stems from the country’s peculiar geography. India, a country of sub-continental size and situated between the latitudes 8⁰4’ N and 37⁰6’ N and longitudes 68⁰7’ E and 97⁰25’ E, is the tropics largest peninsula in the world and is surrounded by seas on the three sides with an extensive coastline of about 6000 km. With the icy continent of Antarctica as its major neighbour to the south with vast streatch of the Indian Ocean in between. India has the world’s tallest wall (the Himalayas) on its northern boundary. Adjoining the Himalayas further north, is the Tibetan plateau which is large, massive and about 5 km high- a gigantic slab of rock protruding up to the middle of the troposphere and acting as a large sized heat source at the mid- tropospheric level.

India is gifted with a river system involving over 20 major rivers with many tributaries. Physiographically. India comprises seven regions, viz. (I) Northern mountains (the Himalayas), (2) Indo-Gangetic plains, (3) Central highlands, (4) Peninsular plateau, (5) East coast, (6) West coast, and (7) the islands (Andaman & Nicobar Group in the Bay of Bengal and Lakshadweep group in the Arabian Sea).

India’s unique geographical configuration gives it the peculiar climate regime with two monsoon seasons and two cyclone seasons interspersed with hot and cold weather seasons which see considerable thunderstorm activity. The cyclone seasons in the pre-monsoon months (April-May) and the post-monsoon months (October- November) bring cyclonic storms causing large scale inundation, destruction and deaths. The two monsoon seasons (the south west monsoon in June to September and the northeast monsoon in November- December bring forth rains-many a times in intensities and amounts sufficient to cause serious floods creating hazardous (and often disastrous) situation. In fact, floods and cyclones are the two major natural disasters which visit India quite often. The adverse impacts of these two natural disasters cannot be assessed merely in rupee terms based on destruction of crops, property and infrastructure because the toll of human misery in the form of death, disease, injury, loss of employment, psychological trauma, and above all the set-back to development are too difficult to compute.

2. INDIA’S RAINFALL REGIME

At this stage, it will be useful to have an appreciation of the rainfall regime of the country as both these natural disasters (floods and cyclones) are rainfall related.

The long term average annual rainfall for the country as a whole is 116 cm- again the highest for a land of comparable size in the world. But this rainfall is highly variable both in time and space. The heaviest rains occur over the hilly States in the northeast and along the mountainous west coast (the Western Ghats and the Konkan coast). In contrast, southwest Rajasthan receives hardly 15 cm in a year. The percentage areal distribution of annual rainfall over India is indicated below.

Percentage Areal Distribution of Annual Rainfall over India

Mean Annual Rainfall Corresponding % Area

0-75 cm 30%

75-125 cm 42%

125-200 cm 20%

> 200 cm 8%

The above data point to the areal or spatial variability of the Indian rainfall regime. The rainfall is highly variable in time as well. The maximum rainfall occurs in July and August during the four- month (June to September) southwest monsoon season. There are considerable intra- seasonal as well as inter- seasonal variations.

The areal distribution pattern of rainy days (days with rainfall of 2.5 mm or more) generally follows the rainfall distribution pattern indicated above. The Western Ghats, the northeastern States, and sub-Himalayan West- Bengal have more than 100 rainy days. In the extenreme west Rajasthan, the number of rainy days is less than 10. In the northern plains, the number of rainy days decreases from east to west. In the peninsular region of the country, the semi- arid areas (from Madhya Mahrashtra to Tamil Nadu) have between 40 and 50 rainy days on the average. The number of rainy days in the central parts of the country comprising Orissa, Madhya Pradesh and the adjoining Andhra Pradesh varies between 50 and 75.

The seasonal distribution of rainfall over India is quite interesting. The southwest monsoon season extending from June to September is the principal rainy season and it accounts for about 80% of the annual rainfall of the country as a whole. Even Tamil Nadu, which is regarded as a shadow zone during the southwest monsoon season, receives almost 50% of its annual rainfall during the season. The post-monsoon season (October and November) brings rains to peninsular India especially the east coast through the mechanism of northeast monsoon and cyclonic storms. The winter season (December to February) is characterized by occasional visits of cyclones to the more southern parts of the country, and by western disturbances which given rain over northwest India, particularly the States of Jammu & Kashmir, Punjab, Himachal Pradesh, the hills of west Uttar Pradesh (Uttaranchal) and northern areas of Rajasthan. Then follows the pre-monsoon (hot weather) season of March to May which brings thunderstorm/ duststorm activity over east and north India and cyclonic storms to peninsular India especially the coastal areas.

3. THE SOUTHWEST MONSOON

Since the southwest monsoon is the principal rain giver for India, it is useful to note that the following four mechanisms are responsible for the large variability of the monsoon rainfall

a) The commencement of rains may be early or delayed over the whole country or a large part of it. (Early or delayed onset of the monsoon)

b) There may be extended periods of no or little rain during the normally most active months of July and August. (prolonged onset of the monsoon).

c) Rains may end considerably earlier than normal or may prolong. (Early or late withdrawal of the monsoon)

d) Rains may persist or prolong unusually in one part of the country and shun other regions. (Erratic distribution of the monsoon)

It is the inherent variability of the rainfall over India, and particularly during the monsoon season, both in time and space that makes India especially vulnerable to floods.

4. FLOOD AND CYCLONE DISASTERS

Floods and cyclones are the natural disasters where excess of water (rains) creates the havoc. In case of cyclones, the wind fury and the inundation of coastal areas by the selfish sea water of the accompanying storm surge add to the destruction and misery. In case of floods, the swollen rivers with overflowing banks do the damage in flood plains. Of late, flooding or water logging is becoming a major problem in urban and metropolitan areas. Cyclonic storms pose a hazard mainly in coastal regions (more on the east coast as compared to the west coast) but no place in the country is free from floods (even Rajasthan suffers from floods and flooding) although flood plains of rivers and cyclone- affected coastal regions are most prone to floods. While cyclone is a natural disaster in the full sense of the term, flood problem (including flooding) is seriously aggravated by human activities such as overgrazing, deforestation, soil erosion siltation, and thoughtless construction. It is worthy of note that on the average the area actually affected by floods every year in the country is of the order of 10 million hectares of which about half is cropland. In fact, according to the report of the Rastriya Barh Aayog, the area prone to floods in the country is of the order of 40 million hectares and that estimate was made two decades ago.

It is in this background that the forecasting and warning of floods and cyclones assume great importance. But before describing the forecasting and warning system operational in the country for dealing with floods and cyclones, it would be advisable to understand the significance of the concepts of predictability, forecasting and warning (and their inter- relationship) as applicable to the natural disasters such as floods and cyclones.

5. PREDICTABILITY, FORECASTING, AND WARNING AND THEIR INTER-RELATIONSHIP

As has been brought out in the preceding Sections, the occurrence of flood and cyclones is highly variable in time and space although there are preferred locations (coasts for cyclones and riverine flood plains for floods) and seasons (monsoon for floods and pre-monsoon and post-monsoon seasons for cyclones). Furthermore, no two events are similar. When a flood or a cyclone recurs, it would certainly differ in intensity, coverage, duration and impact. The variability is inherent in the very nature of floods and cyclones. This is all the more the reason that we should appreciate the concepts of predictability. Forecasting and warning in the context of floods and cyclones.

Predictability

Predictability of a disaster is the key to understand its nature and thereby assess the probability of its occurrence and the anticipated fury of the event. In the sense, predictability is an attribute amply applicable to natural disasters such as floods and cyclones. It has no relevance for natural disasters such as earthquakes nor for man-made disasters such as industrial disasters where a human error or a mechanical fault is responsible for turning a hazard into a disaster.

In case of floods, the predictability in practical terms pertains to that of heavy monsoon rains at any place or time. There are additional aspects that need to be considered because these determine whether a particularly heavy rainfall would result in floods or flooding. For example, repeated or persistent occurrence of rainfall over an area already soaked with rain will certainly result in flooding or flood. Excess water in a river, due to heavy and/ or persistent rains in the catchment area or the upper regions of the river system will create flood downstream. Absence or lack of adequate drainage in any area will aggravate the flooding. Hence the predictability of floods hinges on, i) the predictability of rainfall (read predictability of monsoon), ii) antecedent rain condition of the area, iii) whether a river or a stream flowing through the area is bringing excess water from upstream regions, and (iv) if there is a drainage problem resulting in accumulation of water in the area. As all these aspects are either predictable in advance or monitor-able in real time, it is reasonable to conclude that floods have a reasonable good predictability.

Cyclones have the best predictability among all the disaster phenomena. This is because their formation (cyclogenesis) and subsequent behaviour are fairly well understood. Furthermore, cyclones can be detected as soon as they form over oceans and can be kept under continuous watch through meteorological satellites and radars. The magnitude of the accompanying hazard of storm surge is also predictable through techniques which take into account the parameters of the approaching cyclone as well as the physical and oceanographic characteristics of the coast in the area of anticipated landfall i.e. the place where the cyclone is expected to hit the coast.

Forecasting

For the natural disasters that possess a fair degree of inherent predictability such as floods and cyclones, forecasting is the next step in disaster reduction. But forecasting has to be based on sound scientific principles and operationally proven techniques. Forecasting has to be done by an authorized agency, institution or individual who, besides being competent, experienced, responsible and accountable, is conscious of the end-use of the forecast, its implications, and the dependence of the success of disaster reduction on the forecast. In order to be effective, a forecast has to be worded clearly and unambiguously and it has to reach the users as quickly as possible.

Flood forecasting for rivers means basically that an estimate is made of the future stages or water levels in the river at selected points along the river during flood season. The aim is to forecast the crest and its time of occurrence at a place along the river. For this, it is necessary to have the relevant hydrological data such as the characteristics of the river basin and the flood plains and hydro meteorological data like the rainfall in the catchment area, weather forecast, current levels of water and flow in the river.

For floods other than river floods such as flash floods, and water-logging due to inadequate drainage, forecasting takes the shape of monitoring because forecasting of such local events is not practical and the only effective method is to mount a monitoring and reporting system locally.

Forecasting of cyclones is quite well developed. The cyclone forecasters (meteorologists) are able to detect the formation and subsequent movement of cyclones of weather charts that they prepare regularly, either manually or computer- generated, based on observations of atmospheric pressure, temperature, humidity and winds near the earth’s surface and at different levels in the atmosphere. Simultaneously they locate and track the cyclones through satellites and high power cyclone detection radars. The image of cyclone from satellites and radars enable a constant monitoring of the intensification or weakening of the cyclone.

Even then, forecasting of the movement of a cyclone and the landfall point, i.e., the place where it will hit the coast, is a highly skilled task. Cyclones do not travel in straight lines. Their tracks are usually curved and cyclones often make small loops as they go along. Cyclones do not maintain a constant speed along their path. Sometimes they slow down or remain stationary or suddenly increase their speed. Therefore a cyclone is kept under constant surveillance and the forecast is frequently updated.

Warning

Once a forecast is available regarding an anticipated disaster event, it has to be converted quickly into an area-specific and time-specific warning. Furthermore, the warnings also need to be user- specific because the capacity of different users to withstand the onslaught of a disaster is different. For example, the general warnings for the public would be different from those required specifically for the safety of a railway bridge during cyclone conditions because a strong structure such as a railway bridge is designed to withstand a certain force of high winds and to permit a certain level of river water buffeting it pylons. Warnings in this case need to be issued only if the anticipated cyclonic winds and river-flow are expected to go beyond the specified safety thresholds. However for the public, where houses of various types and strengths including the hutments in low lying areas have to face the fury of cyclones and/or floods, the warnings have to be in terms of the anticipated winds and rainfall in the hope that the individuals and the communities will be prepared and take prompt action with the help of government and non-government organizations wherever the anticipated impacts are likely to be dangerous. It is important to emphasize that a warning has no value unless it reaches the users quickly and well in time. Therefore quick communication is very important at the warning stage.

Inter-relationship

The inter-relationship between Predictability, Forecasting and Warning is self-evident and would have been clear from the discussion in the preceding paragraphs. To repeat, a warning can only be issued on the basis of a useful forecast and a disaster can be forecast only if it has an inherent predictability about it.

Event if an event is predictable, a useful forecast is available, the appropriate warning has been issued and it has reached the users in time; the whole exercise will be fruitful only if the warning is believed and acted upon by the users. Therefore credibility is very essential at every stage of the process of forecasting and warning. That is why the concerned agencies strive hard to build credibility for their forecasts and warnings so that users develop confidence in these and take required action immediately and effectively.

While it is not possible to prevent the occurrence of natural disasters, it is certainly possible to reduce the resultant disastrous effects through adequate preparedness and timely action. The effectiveness of timely action is generally enhanced through accurate forecasts and clearly worded prompt warnings. Herein lies the importance and significance of forecasts and warnings of natural disasters such as floods and cyclones.

The significance of warnings is well summarized in the Manual of Disaster Prevention and Mitigation, Preparedness Aspects issued by the United Nations Disaster Relief Organization (now called the United Nations Department of Humanitarian Affairs) which states:

“ It is axiomatic that if timely warning can be given of an impending or probable event which may bring disastrous consequences in its train, then it will be possible to reduce the severity of those consequences. The degree to which the reduction can be effected will depend upon the interplay of three main elements namely:

- the accuracy of the warning:

- the length of time between the warning being issued and the expected onset of the event; and

- the state of pre-disaster planning and readiness

Included within this last element is a sub-element that is the degree to which the public respond to the warning and take correct precautionary action”.

Therefore the credibility of a warning is the touchstone of its effectiveness.

6. THE FLOOD FORECASTING AND WARNING SYSTEM IN INDIA

Flood forecasting and warning constitute a reliable and cost-effective (therefore very important) non-structural measure for flood related disaster reduction. Flood forecasting and warning involves two aspects viz., (i) heavy rainfall forecasting and warning and (ii) river related flood forecasting and warning. Heavy rainfall forecasts and warnings are issued by the India Meteorological Department (IMD) on the basis of the prevailing meteorological conditions (synoptic situation) taking into account the climatologic as well as the intensity and persistence of the on-going rain-producing weather phenomena such as troughs. Depressions and cyclones. Heavy rainfall forecasts and warnings are also disseminated to the public through radio, television and newspapers in the concerned area in local language (s).

The present day riverine flood forecasting and warning system in India has a 40 year history dating back to the establishment of the first Flood Forecasting Station at Delhi Railway Bridge on river Yamuna in 1958. The first flood forecast was issued on 25 July 1959 for this station. Since then, the flood forecasting organization of the Central Water Commission (CWC) has expanded gradually to a network of 157 Flood Forecasting Stations located in 11 States and 2 Union Territories thus covering most of the major inter-State rivers in the country. Bihar, being the most flood prone state, has

the largest number of Flood Forecasting Stations followed by other States and Union Territories as indicated below.

Bihar	36
Uttar Pradesh	33
Assam	23
West Bengal	14
Orissa	11
Andhra Pradesh	11
Gujarat	10
Maharashtra	7
Karnataka	4
Madhya Pradesh	3
Delhi	2
Dadra & Nagar Haveli	2
Haryana	1

On the average, about 6000 flood forecasts are issued annually- most of these during the monsoon months. Flood forecasts are issued daily between May and October in order to take care of likely floods due to cyclones and monsoon rains. As in the case of dissemination of heavy rainfall forecasts and warnings by IMD, the flood forecasts from CWC are addressed to the specific users including the State Governments and District authorities and are made public through electronic and print media. Flood forecasts, in the form of computer generated daily bulletin from CWC, are also made available in all the district through NICNET, the countrywide computer network of the National Informatics Centre (NIC) of the Government of India.

The warning responsibility in case of floods is taken up by the State Governments and their District Administrations. The State governments, based on the local experience, fix ”Danger Levels” for a river at vulnerable places such as near cities or bridges. If the local conditions change, the “Danger Level” can be refixed. CWC issues flood forecast when the river level at a given place reaches or is expected to reach the “Warning Level” which is usually one meter below the “Danger Level”. CWC issues flood forecasts in the form of “Daily Water Level and Flood Forecast Bulletin”. During flood seasons. State governments set up Control Rooms at the State and District Flood Forecast Bulletin”. During flood seasons, State Governments set up Control Rooms at the State and District Headquarters which receive the forecasts from the Flood Forecasting Stations of CWC, convert these into place-specific warnings to the relevant locations and also take appropriate action. The warnings are regularly updated as new observations and forecasts are received.

The inputs to the flood forecasting system come from the field observational networks of the two agencies of Central Government viz., the India Meteorological Department (IMD) and the Central Water Commission (CWC) although the nodal agency for formulating flood forecasts is the Central Water Commission (CWC). The meteorological inputs to the system are provided by the Food Meteorological Officers (FMO) network of IMD.

Flood forecast formulation procedures involve collection of hydrological and hydro meteorological data. Past data are utilized for development / refinement of flood forecasting techniques. The forecast at a Flood Forecasting Station is generally formulated for river stage and its time of occurrence. For reservoir regulation, forecast is given for inflow and its distribution in time. For formulating flood forecasts, various graphical techniques, rainfall-fun off models, application of unit hydrograph, and computer modeling methods are used.

In summary, the flood forecasting system of CWC involves the following steps:

i) Hydrological and hydrometeorological observations at the field networks of CWC and IMD.

i) Transmission of data from field to Flood Forecasting Station (via IMD’s Flood Meteorological Offices in case of Hydrometeorological data.)

ii) Data processing and formulation of flood forecast at CWC’s Flood Forecasting Stations.

iii) Dissemination of flood forecasts to users.

iv) Flood forecast monitoring and evaluation.

The last step i.e., monitoring and evaluation of flood forecasts is a very significant step and CWC attaches great importance to it. For this purpose and to ensure unbiased evaluation, a software package FFWNPAS (Flood Forecasting and Warning Network Performance Appraisal) has been developed. This software package is capable of evaluating the performance of CWC’s Flood Forecasting Stations Network as well as on-line monitoring of any unusual flood situation by producing a hydrograph.

According to the norms followed by CWC, a flood forecast is considered to be reasonably accurate if the difference between the forecast level and the corresponding actual level of the river at the forecast place and time is within + 15 cm. Forecast accuracy performance based on this criterion is assessed for each forecast issued from the network of flood forecasting stations and later CWC evaluates the overall performance of the flood forecasting system as a whole. The performance of the past years has been well documented and published by CWC every year since 1986. An overall accuracy of 90-95% has been claimed for the flood forecasts which means that 90-95% of the flood forecasts satisfy the accuracy criterion mentioned above.

More is needed

The existing flood forecasting system provides macro scale service only. As structured at present, the system does not cater to remote areas (such as small communities in the hills) and basins served by small streams. But such areas do have recurrent flood problem. Moreover such communities are often economically disadvantaged. General wide area forecasts of heavy rain result in apathy or over action and credibility suffers. Flash floods in mountainous areas result mostly after a temporary blockage of natural flow of rain or stream water. Here local detection and timely action through a system of community volunteer watch seems to be the answer and such a system should be mounted through panchayats with the assistance of non-governmental organizations (NGOs).

Even in the case of the organized flood forecasting service provided by CWC, there is an immediate need to expand the system to include the States and rivers not yet covered including the intra- State rivers. The observational network needs to have fail-safe telemetry or fast communication channels to cut down the transmission delays. The existing flood forecasting techniques and models need to be refined. A closer coordination between different agencies will certainly upgrade the effectiveness of the flood forecasting and warning system.

Flood warning work carried out in the field by civil authorities such as the revenue officials, irrigation engineers, public works engineers, and municipal bodies, involves informing the people in time and executing rescue, relief and rehabilitation tasks. These arrangements need regular review in association with the concerned sections of the people and competent NGOs (non-government organizations).

7. THE CYCLONE FORECASTING AND WARNING SYSTEM IN INDIA

Cyclone forecasing and warning services are the responsibility of the India Metrological Department (IMD) which was in fact established way back in 1875 in the aftermath of the severe cyclonic storm of 1864 that devastated what was then the province of Bengal. One of the primary objectives for setting up the Department was to issue warnings for cyclones in the Bay of Bengal which disturbed the shipping activities to and from Calcutta- the then capital of British India. It is also interesting to note that the term “cyclone”, from the Greek word meaning the coils of snake, was coined in India by Henry Piddington who, in a series of 23 Memoirs to the Asiatic Society of Bengal in Calcutta, presented detailed account of the ocean storms that occurred during 1839-1851. Thus cyclone forecasting and warning services in India have a long and proud record of over a century and have established a state- of-the art system that is truly of world standard as we shall presently see.

Cyclone forecasting and warning involve the following eight steps:

i) Detection of a weather system of the high seas that shows signs of cyclone formation i.e., cyclogenesis.

ii) Tracking the cyclone once it forms.

iii) Estimating the wind force in the cyclone as it intensifies.

iv) Anticipating its future behaviour i.e. its probable track (speed and direction) and the place and time of landfall on the coast.

v) Sizing the eye of the cyclone and interpolating the central pressure in the eye and the associated winds especially at and after the landfall.

vi) Estimating the height, time and place of the storm surge.

vii) Assessing the likely rainfall as the cyclone moves overland and degenerates into a deep depression/ depression.

viii) Formulation and dissemination of forecasts and warnings at each significant stage and at regular time intervals.

In order to accomplish the abovementioned steps in the process of cyclone forecasting and warning, the India Meteorological Department (IMD) utilizes the data from the following sources:

i) Routine weather observations from IMD’s own surface and upper air meteorological observations network operating round the clock.

ii) Weather reports from about 280 merchant navy ships that constitute the Voluntary Observing Fleet.

iii) Weather reports (aireps) from commercial aircraft.

iv) Radar reports from IMD’s 10 high power cyclone detection radars on the coasts.

v) Day and night cloud imagery from INSAT geostationary satellite and the satellite derived data such as the long-wave outgoing radiation and the cloud motion vectors (satellite derived winds).

The meteorological data from the network and from ships and aircraft are very important for synoptic analyses and computation of parameters such as convergence, vorticity, and steering wind field which enable an exhaustive scientific assessment of the energetic of the cyclone and its prognosis including its likely track and the associated wind and rain field. This exercise is done in a man-machine-mix mode in which the skill of an experienced cyclone forecaster and the validated computer models are made use of.

Cyclone detection radars and INSAT play important roles in the cyclone forecasting and warning system as they keep the cyclone under watch all the time and provide real time data instantaneously. While radars probe the cyclone from the ground, the satellite provides the view from the top.

IMD’s cyclone detection radar network where each circle denotes the coverage of each radar which extends to 400 km around the radar. It will be seen that there are 6 cyclone detection radars on the east coast and 4 on the west coast. It may be recalled that the incidence of cyclones is greater on the east coast as compared to the west coast.

There are two special features of IMD’s powerful radar network. Firstly, its combined coverage is so dense that no cyclone can come near the coast without being detected by one or more of these radars. Secondly, the dense radar network is designed to provide an overlapping surveillance in such a manner that even if one or two radars are not operational at the crucial moment for any reason whatsoever ( a rare occurrence, if at all), any cyclone will still be under the watch of one or more radars. It is gratifying to note that this cyclone detection radar network is to be gradually upgraded to a network of more versatile Doppler radars within the next two years or so.

Once the current status of a cyclone and its forecast behaviour are available, the next step is to formulate the area-specific cyclone warnings which are addressed to the concerned State Governments, Defence Services, railways, Telecom agencies, airports, seaports, fisheries departments, special users who have requested specific warnings and the general public (through the electronic and print media). At the Central Government level, the Central Relief Commissioner in the Ministry of Agriculture, Cabinet Secretariat and Prime Minister’s Office are kept updated on the status of the cyclone. Immediately on receipt of the first information regarding a cyclone, the Crisis Management Committee, the Crisis Management Group and the Control Rooms get energized at the Central level, the concerned State Government also initiating similar action through the State Relief Commissioners.

IMD issues cyclone warnings in two stages. In the first stage, a “CYCLONE ALERT” is issued about 48 hours before the likely commencement of adverse weather on and along the coast. A “CYCLONE WARNING” is issued about 24 hours before the likely landfall i.e., 24 hours before the cyclone is expected to hit the coast. Of course, warnings to ports and fisheries officials start much earlier as these are particularly vulnerable. In fact, fishermen are warned not to venture out to the sea as soon as a threat of cyclonic conditions is perceived in their area of operation.

IMD has developed mathematical models to make objective (Computer generated) forecasts of cyclone tracks and the anticipated storm surge at the time of landfall. The cyclone warnings contain information about the likely place and time of landfall and the height of the associated storm surge.

It is not sufficient that the cyclone warnings reach the State Governments at their headquarters and then the warnings move to the local level through administration channels however quick these might be. Time being of the essence in disaster management, cyclone warnings should reach the target area simultaneously and preferably in the local language. If the target area happens to cover more than one State, it is advisable that the warnings are issued to each part of the area in the relevant language. Issuing an omnibus multilingual message will be counterproductive. Each warning should be succinct and in the required language. It should reach each target area quickly and simultaneously. This has been made possible through the Disaster Warning Services (DWS) provided by INSAT.

The cyclone warnings originate from IMD’s Area Cyclone Warning Centres (ACWCs) at Calcutta, Chennai and Mumbai with the IMD Headquarters at New Delhi providing the guidance and coordination. The ACWCs are assisted by three Cyclone warning Centres (CWCs) at Bhubaneshwar, Visakhapatnam and Ahmedabad. It may be noted that the ACWCs and CWCs between them cover all the cyclone prone States. The cyclone warnings for direct dissemination to the desired target area are prepared in the appropriate language(s) and directly broadcast from the concerned ACWC to the target area via the INSAT. In the target area, a DWS receiving station needs only a dish antenna, receiver, and a siren. Such sets are installed in selected villages, schools, panchayats, revenue offices, police stations, and district offices. As DWS does not involve any terrestrial wires, poles or cables, this communication system is also not disturbed by cyclonic winds or heavy rains and the warning and de-warning massages are disseminated without the threat of disruption. DWS is an indigenous concept which has proved its worth during cyclone situations in the past many years. There are already 250 DWS receiving stations in the field in the cyclone prone States and further expansion is planned.

For warnings to seafarers, there is an elaborate system of cyclone warning signals in the form of large visual displays of different shapes (cylinder, diamond and other shapes) that are prominently hoisted at seaports. These large signals of different shapes and combinations- visible from a distance on the sea- denote different status of anticipated danger from cyclonic weather or cyclone itself. These storm warning signals are of great help to small boats and fishermen who do not have the type of fast communication apparatus that large ships have.

It is worthy of note that IMD’s responsibility in respect of cyclone forecasting and warning is for a region larger than the Indian territory. By international arrangement under the aegis of the World Meteorological Organization (WMO) which is a Specialized Agency of the United Nations, IMD New Delhi is designated as the Regional Specialized Meteorological Centre for Tropical Cyclones (RSMC- Tropical Cyclones). In this capacity, it deals with all the cyclones that generate in the Bay of Bengal and the Arabian Sea and issues “advisories” to neighbouring countries if their territories are approached by a cyclone. There are only three such designated centres in the northern hemisphere viz. RSMC-Tropical Cyclones at New Delhi (India), RSMC- Typhoons at Tokyo (Japan), and RSMC- Hurricanes at Miami (USA). In short, the cyclone forecasting and warning system in India is a proven system recognized nationally and internationally.

More is needed

Yet, the system can be made even more effective. Apart form large scale expansion of the INSAT Disaster Warning Service (DWS) by installing more DWS receiving stations in the field, a system of aircraft reconnaissance flights will be very helpful. Such a cyclone probing aircraft flight facility will be able to give the most reliable data on the exact location of the eye (centre) of cyclone, the central pressure and the wind field in the cyclone. These precise measurements will enable better modelling of cyclone dynamics and thereby more accurate forecast of cyclone track.