forecast Archives - The India Climate Observatory

Misreading monsoon

May 16, 2019 by Climate portal editor 1 Comment

As usual in May, there is a welter of forecasts and opinions about the monsoon, the great majority of which are short on understanding and shorter on elementary science. The media – newspapers, television news channels, their websites – are to blame for spreading half-baked forecasts and wild prognoses. Not one of the numerous newspapers and TV channels, whatever the language they employ, bother to provide their reporters a basic grounding in the climatological system that gives us our monsoon.

In the first place, the India Meteorological Department (IMD) issues an operational forecast for the south-west monsoon season (June to September) rainfall for the country as a whole in two stages. The first stage forecast is issued in April and the second stage forecast is issued in June. These forecasts are prepared using state-of-the-art Statistical Ensemble Forecasting system (SEFS) and using the dynamical coupled Ocean-Atmosphere global Climate Forecasting System (CFS) model developed under Monsoon Mission of the Ministry of Earth Sciences.

On 15 April 2019 the IMD issued its first stage forecast. Based on our own in-field observations from the west coast, from the patterns of maximum termperature bands and variations in the lower and central peninsular region, from the sea surface temperatures in the Arabian Sea particular its southerly reaches and ditto for the Bay of Bengal, and from the wind patterns that can be experienced at various places in the peninsula and on the west coast, we find the IMD first stage forecast to be reliable.

It is the chronically ignorant media – which over the last few years has displayed a tendency to prefer some so-called private sector weather forecasters instead of what the Ministry of Earth Sciences provides – found irresponsibly claiming that the monsoon of 2019 will be ‘deficient’ and will also begin ‘late’. Neither of these terms is sensible in any way, and we take no satisfaction in noting that only a media that is insensible to planetary and mesoscale events like climate, will employ such insensible terms in reporting that is meant to educate and benefit the public.

IMD’s April forecast used the following five predictors: 1. the Sea Surface Temperature (SST) Gradient between North Atlantic and North Pacific (in December and January), 2. the Equatorial South Indian Ocean SST (in February), 3. the East Asia Mean Sea Level Pressure (in February and March), 4. North-west Europe Land Surface Air Temperature (in January), and 5. Equatorial Pacific Warm Water Volume (in February and March).

There are two forecasts the IMD makes. One is based on the Monsoon Mission CFS Model, which considers global atmospheric and oceanic initial conditions up to March 2019 and use 47 ensemble members (or kinds of data). The forecast based on the CFS model suggests that the monsoon rainfall during the 2019 monsoon season (June to September) averaged over the country as a whole is likely to be 94% ± 5% of the Long Period Average (LPA).

The second is the forecast based on the operational Statistical Ensemble Forecasting system (SEFS). This shows that quantitatively, the monsoon seasonal rainfall is likely to be 96% of the Long Period Average (LPA) with a model error of ± 5%. The SEFS comprises five category probability forecasts for the June to September rainfall over the country as a whole:

Overall therefore the IMD forecast is for the 2019 monsoon rainfall to be near normal. The IMD has already pointed out (which can be seen from the probabilities of the categories given in the table) that there is only a small chance for the monsoon rainfall to be above normal or excess. In view of the weather events and the climatological changes that we are seeing from day to day in May, ascribing a ‘lateness’ to the monsoon is absurd. Monsoon conditions already exist in and over the Indian land mass and in and over the great watery zones extending southwards from latitude 8 degrees North – and that is why we will find rain-bearing clouds crossing the south-western coastline in the first week of June 2019.

Rahul Goswami

Three views of monsoon 2018

May 14, 2018 by Climate portal editor Leave a Comment

The India Meteorological Department (IMD) on 16 April had issued its first long range forecast for the 2018 South-West Monsoon season, which the IMD has historically taken to be 1 June to 30 September. The IMD had said that the “monsoon seasonal rainfall is likely to be 97% of the Long Period Average with a model error of ± 5%”. The IMD had also said that its forecast “suggests maximum probability for normal monsoon rainfall (96%-104% of the long period average) and low probability for deficient rainfall during the season”.

In early June, the IMD will issue its second long range forecast for the 2018 monsoon. Until then, we have studied three of the more reliable (in our view) international multi-model ensemble forecasts for the monsoon. What are ensemble forecasts? Each consists of several separate forecasts (some ensembles use 50) forecasts made by the same computer model – these are run on super-computers such as the High Performance Computer System of the Ministry of Earth Sciences (one is at the Indian Institute of Tropical Meteorology in Pune with 4.0 petaflops capacity and the other at the National Centre for Medium Range Weather Forecasting in Noida with 2.8 petaflops capacity).

The MME forecast is based on estimated precipitation anomalies relative to the period 1993-2016, based on initial conditions calculated at the beginning of May 2018. Four blocks of three months each.

The separate forecasts that make up one ensemble are all activated from the same starting time. The starting conditions for each differ from each other to account as far as possible for the staggering number of climatological, atmospheric, terrestrial and oceanographic variables that affect and influence our monsoon. The differences between these ensemble members tend to grow as the forecast travels two, three, four and more months ahead of the present.

We have considered the ensemble forecasts for the 2018 monsoon of the Multi-Model Ensemble (MME) of the USA National Centers for Environmental Prediction, the NOAA Climate Prediction Center and the European Centre for Medium-Range Weather Forecast (ECMWF). In this order, we find that the MME is optimistic, the NOAA CPC is largely neutral and the ECMWF forecast is somewhat pessimistic. The forecasting periods are in blocks of three months.

Here are the details:

(1) The MME forecast, precipitation anomalies relative to the period 1993-2016, based on initial conditions calculated at the beginning of May 2018.
June July August (JJA) – west coast and Konkan, coastal Andhra Pradesh and Odisha, West Bengal, part of the North-East, the entire upper, middle and lower Gangetic region (Uttarakhand, Himachal, Uttar Pradesh, Bihar, Jharkhand), Madhya Pradesh, Chhattisgarh, Maharashtra and Telengana to have up to +1 mm/day. Rest of India other than Gujarat (-0.5 mm/day) normal.
July August September (JAS) – Gujarat to have up to -1 mm/day, Rajasthan up to -0.5 mm/day, Sikkim, Brahmaputra valley and Arunachal Pradesh up to -0.5 mm/day. Himachal Pradesh and Uttarakhand up to +0.5 mm/day, Madhya Pradesh, Odisha, Chhattisgarh, Jharkhand and West Bengal up to +0.5 mm/day. Andhra Pradesh and Tamil Nadu up to -0.5 mm/day.
August September October (ASO) – Gujarat up to -0.5 mm/day. Tamil Nadu up to -1 mm/day. Kerala and adjacent Karnataka up to -0.5 mm/day. Madhya Pradesh, Chhattisgarh, Odisha, West Bengal up to +1 mm/day. Tripura, Mizoram, Manipur, Nagaland, Uttarakhand, Himachal Pradesh up to +0.5 mm/day
September October November (SON) – Tamil Nadu, Kerala and adjacent Karnata up to -1 mm/day. Maharashtra, Madhya Pradesh, Chhattisgarh, Odisha, West Bengal, Himachal Pradesh and Uttarakhand up to +0.5 mm/day.

The NOAA CPC forecast is based on estimated seasonal precipitation anomalies using initial conditions of 30 April 2018 to 9 May 2018. Three blocks of three months each.

(2) The NOAA CPC forecast, seasonal precipitation anomalies using initial conditions of 30 April 2018 to 9 May 2018.
May June July (MJJ) – for most of India a normal reading (+0.5 to -0.5 mm/day fluctuation) and for the west coastal, Konkan, Kerala, south Tamil Nadu and coastal Andhra Pradesh areas variation of up to +1.5 mm/day.
June July August (JJA) – for most of India a normal reading (+0.5 to -0.5 mm/day fluctuation).
July August September (JAS) – normal for most of India. Some areas in the central Deccan plateau, on the west coast and east coast variation of up to -1 mm/day.

The ECMWF forecast is based on estimated mean precipitation anomaly based on climate period data of 1993-2016 and initial conditions as on 1 May 2018. Four blocks of three months each.

(3) The ECMWF forecast, mean precipitation anomaly based on climate period data of 1993-2016 and initial conditions as on 1 May 2018.
June July August (JJA) – all of the southern peninsula and part of the Deccan region (Kerala, Tamil Nadu, Karnataka, Andhra Pradesh, part of Telengana up to -100 mm for the period. West Bengal, Bihar, Jharkhand, Uttar Pradesh up to +100 mm for the period.
July August September (JAS) – all of the southern peninsula and the Deccan region – Kerala, Tamil Nadu, Karnataka, Andhra Pradesh, part of Telengana and Maharashtra up to -100 mm for the period.
August September October (ASO) – Maharashtra, Telegana, Andhra Pradesh and Karnataka up to -100 mm for the period.
September October November (SON) – Central and western India, eastern states and entire Gangetic region up to -50 mm for the period.

Rahul Goswami

The ‘Hindu’, ignorant about weather and climate, but runs down IMD

September 2, 2016 by Climate portal editor Leave a Comment

We find objectionable the report by ‘The Hindu’ daily newspaper accusing the India Meteorological Department of scientific shortcoming (‘IMD gets its August forecast wrong’, 1 September 2016). The report claims that the IMD in June 2016 had forecast that rains for August would be more than usual but that the recorded rain was less than usual.

This is nothing but cheap sensationalising by the newspaper of a non-issue. In so doing the ‘Hindu’, which is considered one of Bharat’s national newspapers, has attempted to tarnish the work of not only the India Meteorological Department, but also the work of the earth observation technical community which serve us in the several institutions and agencies of the Ministry of Earth Sciences.

There is no mainstream news media in the country – no daily newspapers, no magazine or periodical, no television channel, no internet website – which possesses the competence to assess the scientific quality and correctness of output of the government earth science agencies, and whose output is delivered to the public every day, several times a day. ‘The Hindu’ certainly does not and with this report exposes its ignorance about meteorology and climate science and observation.

Concerning the newspaper’s claim, rainfall for the period 1 June to 31 August in the 36 meteorological sub-divisions of Bharat, as an area-weighted average, is -3% of the long period average and is therefore well within the boundaries set by both the first stage and second stage forecasts provided by the IMD. Of the 36 sub-divisions, for this period 24 sub-divisions have recorded normal rainfall, four have excess and eight (including the two island sub-divisions) have deficient rainfall. In what way is this an erring forecast?

The news report in the ‘Hindu’ states that the forecasting error it has found “suggests that the agency’s weather models are still not robust enough to capture changes in global climate that could affect” our monsoon. This is nonsense.

The earth observation agencies of the MoES – of which the IMD is a part – for the June to September monsoon forecast employs a group of six parameters that inform the forecast (together called an ensemble forecasting system). These are: north-east Pacific to north-west Atlantic sea surface temperature anomaly gradient, south-east equatorial Indian Ocean sea surface temperature, East Asia mean sea level pressure, central Pacific (El Nino region 3.4), sea surface temperature and tendency, north Atlantic mean sea level pressure and north-central Pacific 850mb wind gradient. In what way does this not look at global climate?

Moreover, the IMD and the agencies of the MoES (notably the Indian Institute of Tropical Meteorology) work closely regionally and internationally on climate science, weather prediction and monitoring. Not only is the IMD implementing for the World Meteorological Organisation (WMO) a Regional Climate Centre for South Asia, the monsoon prediction and monitoring system relies on collaboration with: the National Centers for Environmental Prediction (NCEP) of USA, the European Centre for Medium-Range Weather Forecasts (ECMWF), the Japan Meteorological Agency (JMA), the Met Office Hadley Centre for Climate Science and Services of UK, and with the national meteorological agencies of Bangladesh, Bhutan, the Maldives, Myanmar, Nepal, Pakistan, and Sri Lanka.

And furthermore, it is because the Earth System Science Organisation agencies and institutes revise, review and upgrade forecasting models, computing wherewithal and methods continuously that we have in 2016 an experimental forecast (based on the Monsoon Mission coupled dynamical model).

‘The Hindu’ newspaper has presented its own uninformed reading of differences in forecast averages to make an absurd claim against the IMD, neglecting entirely to mention the extremely valuable service provided, at the district and even at the block level, to Bharat’s kisans via daily sms on weather which will affect crops; neglecting the several excellent initiatives launched by the Department since 2015 on localising forecasts for towns and cities (in close coordination with the National Remote Sensing Centre of the Indian Space Research organisation, the Meteorological and Oceanographic Satellite Data Archival Centre of ISRO’s Space Applications Centre, and the Indian National Centre for Ocean Information Services.

Monsoon outlook for June and July

May 29, 2016 by Climate portal editor Leave a Comment

At the end of May 2016, based on a reading of the seasonal forecasts of our Earth System Science Organisation group (under the Ministry of Earth Sciences) and complemented by the collaborative seasonal forecasts of the NOAA Center for Weather and Climate Prediction, we have prepared an outlook for the June and July monsoon 2016 months.

The regional rainfall outlook for June and July 2016. Green hues are +0.25 to +1mm/day averaged over the outlook period.

The outlook shows: (1) that our main concern of whether the first stage monsoon forecast of the IMD remains true is fulfilled, which is, that the 2016 monsoon will be normal (and better than normal in some regions); (2) that our next most important concern of whether any region will have significantly below normal rainfall is also addressed, and under the current forecasts there is no such region; (3) that the June and July rains will be at least normal in most states and meteorological sub-divisions.

Some provisos need to be observed. The seasonal forecasts are released for three month spells (May to July, June to August, and so on). Depending on the kind of modelling that is followed (and there are several) the outlooks are updated or modified every 10 days to fortnightly to monthly. These updates are based on what are called ‘initial conditions’ which for our current outlook is the first half of May.

Here is a more detailed regional outlook for June and July 2016:
• Tamil Nadu and Kerala will have rain that over the season is +1 to +1.25mm/day.
• Karnataka, Andhra Pradesh and Telengana, Madhya Pradesh, most of Maharashtra, all the states of northern and north-west India, Uttar Pradesh and Bihar, Sikkim, Arunachal, lower Assam, western Meghalaya, and Lakshadweep will have rain that that over the season is +0.25 to +1 mm/day.
• Odisha, Chhattisgarh, southern Jharkhand, gangetic West Bengal, eastern Vidarbha (Maharashtra), the north-eastern half of Telengana, north coastal Andhra Pradesh, upper Assam, Nagaland, Manipur, Mizoram and Tripura will have rain that over the season is -0.2 to +0.25mm/day and Andaman and Nicobar islands will have rain that is up to -0.5 mm/day.

This outlook we will amend between June 10 and 15 as the ESSO’s forecasts and international collaborative monsoon forecasts are updated.

Prepare for May heat

May 4, 2016 by Climate portal editor Leave a Comment

The heat outlook for the first half of May, which was released by the India Meteorological Department (IMD) on 02 May, calls for immediate attention and preparation on all fronts.

The forecast is for three periods of five days each (called pentads) with expected temperature anomalies given for maximum and minimum temperatures. The big picture is that over some parts of the country maximum temperatures will remain 3-4 C above normal for all the three pentads.

Minimum temperatures that are 1-5 degrees higher than normal will increase in terms of the geographical range as the days progress through the first, second and third pentad: 02 to 06 May, 07 to 11 May and 12 to 16 May.

There are several particular alerts arising from the IMD heat wave outlook:

The heat outlook for the first half of May, released by the India Meteorological Department (IMD), for the three five-day periods of 02 to 06 May, 07 to 11 May and 12 to 16 May.

1. Odisha, Gangetic West Bengal and south Chhattisgarh, which have seen some record-breaking high temperatures in April, will continue to see above normal maximum temperatures.

2. South Interior Karnataka, coastal Maharashtra and Goa (the Konkan), and Saurashtra will experience a gradual rise in maximum temperatures from the first to third pentad.

3. Maximum and minimum temperatures both, in Jammu and Kashmir, Himachal Pradesh and Uttarakhand will remain around 5 C above normal for the duration of the forecast.

4. The 12 to 16 May period (third pentad) will see higher than normal maximum temperatures (2 to 5 C) over almost the entire country, and higher than normal minimum temperatures over most of the country.

Other observations are:

5. The North-East will experience minimum temperatures about a degree higher than normal during 07 to 16 May.

6. For the second pentad, that is 07 to 11 May, maximum temperatures in north-west India (Punjab, Haryana, western Uttar Pradesh, Rajasthan, western Madhya Pradesh, Delhi) will drop by 2 to 3 C.

7. Coastal Andhra Pradesh, Rayalaseem and Tamil Nadu will experience lower minimum temperatures by 1 to 2 C during 07 to 16 May.

Please observe basic precautions during this period in particular: eat smaller meals more often; drink water even when not thirsty; avoid tea, coffee and alcohol; plan your activities to avoid being outdoors during 11am to 4pm; do not leave children in cars by themselves; keep a watch on the elderly especially those who are infirm or invalid; wear non-synthetic non-polyester light-coloured and loose fitting clothes; if working outdoors rest frequently; provide drinking water and shade to animals and pets.

A monsoon in more than two halves

August 4, 2015 by Climate portal editor Leave a Comment

Less rain for the remaining two months of the typical monsoon season of four months, but an overall season average that remains as it was forecast in June. This is the confusing monsoon update issued by the Earth System Science Organization (ESSO), the Ministry of Earth Sciences (MoES) and the India Meteorological Department (IMD).

There are aspects of IMD’s treatment of the monsoon season that need correction in our view. One is the long range forecast and its updates. Specific to this update, we are at the halfway stage of what is typically considered the four month monsoon (this too needs revision, as April and May rains were not the usual ‘unseasonal’ passing showers). However, any downward revision of the rainfall average for August and September ought to be an overall downward revision of the season, particularly as June-July have seen very uneven rain.

Consider the highlights of the updated monsoon forecast:

* Quantitatively, the rainfall over the country as a whole during the second half of the season (August to September) is likely to be 84% of LPA with a model error of ±8%.
* The rainfall during August is likely to be 90 ± 9% of LPA as was forecasted in June.
* The season (June to September) rainfall over the country as a whole is likely to be 88% of LPA with a model error of ±4% as was forecasted in June.

We make our criticism constructively, for a significant amount of the material India Climate Portal puts out through our website and our twitter account is taken from the public products released by IMD, ISRO and the Ministry of Earth Sciences, and we fully appreciate the quality of work and commitment of these agencies.

The national mean rainfall (“country as a whole”, as the IMD forecasts call it) must be abandoned as it does not represent the meteorological diversity of a very large country. Each of the 36 met sub-divisions is affected in different ways by the El Nino Southern Oscillation, the Indian Ocean dipole, the Madden-Julian Oscillation and other hemispheric phenomena.

There is no need for this simplification, which in fact achieves the opposite of timely accuracy.
The media in particular (television and radio, print, online) look for an overall message and, without guidance from authorities, picks up ‘top line’ messages that are of little or no use at the district and taluka level, and also for towns and cities. The question for IMD is rather: how will variability in monsoon together with the strengthening El Nino affect local outlooks for August to October. That is why we advocate monthly outlooks for the 36 met sub-divisions, to begin in May and to run until October (that is, half the year and not a third of the year), primarily to prepare local administrations for all possible scenarios.

There is no reason why this cannot be the approach. The Ministry of Earth Sciences coordinates the observation network (satellites included, and our agencies ISRO and NRSC are heavily involved), the IMD uses these data together with a very extensive network of weather stations all over India. The output is excellent quality and in the public domain. Because the meteorological services in India have historically been designed to aid and guide agriculture and cultivation, the agri-met bulletins, alerts and products are copious. Hence IMD/MoES listens to the needs of the agricultural departments and, more recently, disaster management agencies. Unfortunately, the interface with public is still minimal, which this central government can also easily remedy.

Two years of India’s weather watcher

July 28, 2015 by Climate portal editor Leave a Comment

We wish Insat-3D a very happy second birthday and warmly congratulate the Indian Space Research Organisation (ISRO) on this anniversary.

Insat-3D completed two successful years in orbit on 26 July 2015. The Advanced Weather Satellite is designed for enhanced meteorological observations and monitoring of land and ocean surfaces for weather forecasting and disaster warning. Insat-3D is the first Indian geostationary satellite equipped with instruments that provide frequent good quality atmospheric profiles (temperature, humidity) over the Indian landmass and adjoining areas.

Thanks to the coordination between ISRO and the Indian Meteorological Department (IMD), we at India Climate Portal make heavy and frequent use of the many observational products, all free in the public domain, to inform you about weather and climate.

Insat-3D provides us high quality observations for monitoring and predicting of weather events as well as studying our climate. The advanced ‘Imager’ and ‘Sounder’ on the satellite provide a wide range of atmospheric products such as cloud coverage images, atmospheric winds, sea and land surface temperatures, humidity, quantitative rainfall, earth’s radiation, atmospheric profiles, ozone, atmospheric stability parameters, fog, snow, aerosols. These products are immensely helpful in monitoring day-to-day weather and prediction of extreme events like tropical cyclone, thunderstorm, cloud burst and heat waves.

The ‘Imager’ has completed 25,733 scans and ‘Sounder’ has completed 14,866 scans until the end of May 2015. The Insat-3D spacecraft was dedicated to the country at the National Satellite Meteorological Center (NCMC), India Meteorological Department (IMD), New Delhi on 15 January 2014. An indigenously designed and developed Insat-3D Meteorological Data Processing System processes all data transmitted by the Imager and Sounder. The data archival and dissemination is through IMD, New Delhi and the Meteorological and Oceanographic Satellite Data Archival Centre (MOSDAC, at Space Applications Centre, Ahmedabad).

A number of Insat-3D observations and derived products are being used in models operated by national weather prediction agencies like the IMD and the National Centre for Medium Range Weather Prediction (NCMRWF). Moreover, the European Centrer for Medium range Weather Forecast (ECMWF) and the United Kingdom Meteorological Office (UKMET) plan to use Insat-3D derived data in their global models.

As always, the ISRO family, staff, engineers, scientists and technicians excel at what they do best. In tandem with the committed and dilligent meteorologists of the IMD, they have given us free information, as good as the best the world can offer, so that we understand our Bharat better.

Being prudent about forecasts

June 3, 2015 by Climate portal editor Leave a Comment

The Earth System Science Organisation (ESSO), Ministry of Earth Sciences (MoES) and the India Meteorological Department (IMD) released their second long range forecast for monsoon 2015 on 2 June. The ‘headline’ message is that rainfall for the June to September monsoon season is very likely to be 88% of what is normal for the season.

The forecast has been seized upon by various quarters as having serious implications for the production of crop staples (and therefore for food security), for farmers’ livelihoods, for consumer prices and for the availability of water. These are all valid and important aspects that depend entirely or substantially upon the summer monsoon.

But, the IMD, the ESSO and the MoES do not make statements and forecasts on these aspects. They are concerned with what the climatological data and signs point to, and that is what they have told us. How the forecast relates to important aspects of food, farm incomes, water resources and food stocks relies on interpretations. Our advice – to the media, to government agencies and to the private sector – is to go slow on drawing conclusions and when conclusions are required, to make them incrementally.

The wettest pre-monsoon season (March to May) for five years.

Using the handy graphic here, (887KB) we also point out that the pre-monsoon season (March to May) for 2015 has been the wettest in five years. In several meteorological sub-divisions, excess rain has been recorded during this pre-monsoon season. In several districts, the annual rainfall total has already been reached, even before the typical monsoon season of June to September.

This ought to be warning enough to us to be sparing with deciding how forecasts will affect us. The ESSO, IMD and MoES have repeated, in their second long range forecast, that 2015 is an El Niño year which only means that as this sea temperature phenomenon waxes and wanes though the remainder of 2015, so too will the monsoon system react.

It is best to judge our Indian summer monsoon a week at a time, keeping in mind crop calendars and how much water our reservoirs hold. It is always prudent to take precautions such as rationing water (even when it is raining), especially in towns and cities. Likewise, district administrations will do well to assess their local supplies of food staples and match these figures with what food staples their districts are likely to produce during a monsoon whose reliability has now been written off.

The second long range forecast for monsoon 2015 is available here, and the Hindi text can be found here.

It’s to be a 93% monsoon says the IMD

April 22, 2015 by Climate portal editor 1 Comment

The India Meteorological Department has just released it’s long-awaited forecast for the 2015 Indian monsoon. In terms of the quantity of rainfall over the duration of the monsoon season (June to September) the IMD has said it will be 93% of the ‘Long Period Average’. This average is based on the years 1951-2000.

What this means is the ‘national’ average rainfall over the monsoon season for India is considered to be 89 centimetres, or 890 millimetres. So, based on the conditions calculated till today, the ‘national’ average rainfall for the June to September monsoon season is likely to be 830 millimetres.

There are caveats and conditions. The first is that the 93% forecast is to be applied to the long period average for each of the 36 meteorological sub-divisions, and a ‘national average’ does not in fact have much meaning without considerable localisation. The second is that the forecasting methodology itself comes with a plus-minus caution. There is “a model error of ± 5%” is the IMD’s caution.

This first forecast and the model that the forecast percentage has emerged from are thanks to the efforts of the Earth System Science Organization (ESSO), under the Ministry of Earth Sciences (MoES), and the India Meteorological Department (IMD), which is the principal government agency in all matters relating to meteorology. This is what the IMD calls a first-stage forecast.

As with all complex models, this one comes with several considerations. The ESSO, through the Indian Institute of Tropical Meteorology (IITM, which is in Pune), also runs what it calls an ‘Experimental Coupled Dynamical Model Forecasting System’. According to this, the monsoon rainfall during the 2015 monsoon season (June to September) averaged over India “is likely to be 91% ±5% of long period model average”. (The IMD forecast is available here, and in Hindi here.)

This is a lower figure than the 93% headline issued by the IMD. This too should be read with care as there are five “category probability forecasts” that are calculated – deficient, below normal, normal, above normal and excess. Each is accompanied by a forecast probability and a climatological probability (see the table). The maximum forecast probability of 35% is for a below normal monsoon, while the maximum climatological probability is for a normal monsoon.

As before, time will tell and the IMD will issue its second long range forecast in June 2015. Our advice to the Ministry of Earth Sciences and to the IMD is to issue its second long range forecast a month from now, in May, and also to confirm these forecasts two months hence in June, when monsoon 2015 will hopefully be active all over the peninsula.

Follow the highs and lows of monsoon 2015

April 22, 2015 by Climate portal editor Leave a Comment

Our coverage of the ‘mausam’, the Indian summer monsoon of 2015, has begun. The unseasonal rains of March and April, which have proved so destructive to farmers, have shown why the conventional monsoon season must be widened. You will find all monsoon-related analysis, data and reports here.

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