The Country experienced significantly above normal temperatures during the last two months of January and February,2016, with monthly anomalies of 1.53⁰C & 2⁰C respectively from 1961-90 normal. The year 2015 was the third warmest year ever recorded since 1901. 

During the Hot Weather Season of 2016 i.e. April to June warmer than normal temperatures are expected in all meteorological sub-divisions of the country. Seasonal (April-June) average temperatures over northwest India are expected to be above normal by more than 1⁰C.  Above normal heat wave (HW) conditions are very likely over central and northwest India during the Hot Weather Season of 2016.  

The figures below (Fig.1, Fig.2 & Fig.3) show the forecast for the subdivision-wise averaged maximum, minimum and mean temperature anomalies (departures from the long term normal) respectively over India for the hot weather season (April to June, 2016).  The forecast indicates that during the hot weather season of 2016, temperatures (mean, maximum and minimum) in all the sub-divisions are likely to be above normal. All the temperatures (maximum, minimum and mean) of most of the sub-divisions from northwest India, Kerala from south India and Vidharbha from Central India are likely to be above normal by ≥1⁰C.

The season averaged maximum temperatures of coastal Andhra Pradesh, Odisha, Assam & Meghalaya, sub-Himalayan West Bengal & Sikkim, and Nagaland, Mizoram, Manipur, Tripura are likely to be warmer by <0.5oC and that of the remaining subdivisions are likely to warmer than normal by 0.5 to 1⁰C. 

The season averaged minimum temperatures of sub-Himalayan West Bengal & Sikkim, and Nagaland, Mizoram, Manipur, Tripura are likely to be warmer than normal by <0.5^oC and that of the remaining subdivisions are likely to warmer than normal by 0.5 to 1⁰C.

The season averaged mean temperatures of sub-Himalayan West Bengal & Sikkim, Nagaland, Manipur Mizoram, & Tripura and Assam & Meghalaya are likely to be warmer than normal by<0.5^oC and that of the remaining subdivisions are likely to warmer than normal by 0.5 to 1^oC.  There is also a high probability (76%) of maximum temperatures in the core Heat Wave(HW) zone during the hot weather season of 2016 to be above normal (Fig.4). Core HW zone covers states of Punjab, Himachal Pradesh, Uttarakhand, Delhi, Haryana, Rajasthan, Uttar Pradesh, Gujarat, Madhya Pradesh, Chhattisgarh, Bihar, Jharkhand, West Bengal, Orissa and Telengana and met subdivisions of Marathwada, Vidharbha, Madhya Maharashtra and coastal Andhra Pradesh.  This in turn suggests high probability of moderate and severe heat wave conditions in core HW zone during the hot weather season. 

Many parts of the country experience heat wave conditions during the hot weather season leading to many adverse consequences. Abnormally above normal temperatures can have devastating effects on human health, water resources and power generation and outage.  There is a marked relationship between human mortality and thermal stress. During the summer of 2015, prolonged severe heat wave conditions prevailed over Andhra Pradesh and parts of Telegana which claimed more than 2500 lives.

The recent research analysis suggests that frequency and duration of heat waves over the country are showing an increasing trend. A part of the increasing trend is attributed to increasing greenhouse gases due to anthropogenic activity. In addition, the ocean conditions over the equatorial Indian and Pacific oceans also contribute to the variability of heat waves over the country. In the past, El Nino events over the Pacific are known to cause severe heat wave conditions over the country. 

The strong El Nino conditions over the Pacific Ocean that started in 2015 are still continuing. However, the latest forecasts indicate that El Nino conditions are likely to weaken further and reach weaker El Nino conditions during the hot weather season of 2016.  It has been observed that during the hot weather seasons followed by El Nino years (for example: 1973, 1995, 1998, 2003, 2010, etc. followed by the El Nino years of 1972, 1994, 1997, 2002 and 2009), above normal temperatures including moderate to severe heat wave conditions were experienced in most parts of India.  

In view of its social relevance, India Meteorological Department, Ministry of Earth Sciences has initiated a seasonal outlook for summer temperatures over the country based on predictions using an ocean atmosphere coupled climate model. From this season, IMD will also provide extended range forecasts (5 –day averaged forecasts for next 15 days) of heat wave conditions over the country.  This will be based on the Dynamical Extended Range Forecasting System developed by IITM Pune. The forecast will consist of probability of occurrence of hot days, heat waves and severe heat waves for the next 15 days updated every 5th day from 1st April, 2016 onwards.  The forecasts will be made available through IMD, Delhi website (www.imd.gov.in).

Under the Monsoon Mission, the Indian Institute of Tropical Meteorology (IITM), Pune of the Ministry of Earth Sciences has been developing a state-of-the-art coupled climate model for generating monsoon forecasts known as the Coupled Dynamical Forecast System. The model has a spatial resolution of about 38 km and improved modules of model physics. The model was used to prepare the monsoon forecasts for the 2015 monsoon season. The analysis has shown that the same climate model has useful skill for predicting seasonal temperatures during the Hot Weather Season (April to June) over India. Therefore, this climate model was used to prepare an outlook for the summer temperatures of 2016.  The model climatology was prepared using retrospective forecasts generated for 27 years (1982-2008) based on the February initial conditions. The model showed moderate skill for summer temperatures over many subdivisions over northwest and central India. The forecast for the hot weather season of 2016 was prepared using 47 ensemble member forecasts.

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KSP/VM