Ministry of Earth Sciences Earth System Science Organization

India Meteorological Department

WMO Regional Climate Centre

(Demonstration Phase)

Pune, India

Seasonal Climate Outlook for South Asia

(July to October 2015)

Issued in June 2015

DISCLAIMER: (1) The long range forecasts presented here are currently experimental and are produced using techniques that have not been validated.

(2) The content is only for general information and its use is not intended to address particular requirements.

(3) The geographical boundaries shown in this report do not necessarily correspond to the political boundaries.

During May, moderate El Nino conditions were prevailing over equatorial Pacific with warmer than

normal sea surface temperatures across most of the equatorial Pacific. The latest coupled model

forecast suggests moderate to strong El Nino conditions to establish during the remaining months

of southwest monsoon and post monsoon seasons.

The 2015 JAS & ASO mean season precipitation is likely to be wetter than normal over South of

Myanmar, Sri Lanka & some parts of east India and normal over remaining regions and drier than

normal conditions are likely over North-east India, Bangladesh and Central & northern Myanmar.

The 2015 JAS mean temperatures are likely to be warmer than normal over whole of India,

northern part of Pakistan, Afghanistan, Myanmar, Bangladesh and Sri Lanka. The ASO mean

temperatures are likely to be nearly same as during JAS, except the warmer than normal

temperature likely over some parts of central India and neighbouring western India and normal to

cooler than normal over southern part of India (over Karnataka), Afghanistan & neighbouring

Pakistan.

The country averaged monthly precipitation likely to be normal to wetter than normal for Bhutan

and Nepal in July and drier than normal for remaining countries. In August, it is likely to be normal

to drier than normal for all the countries. In September, it is likely to be normal to wetter than

normal for all countries. In October, It is likely to have wetter than normal for all countries.

The country averaged monthly temperature is likely to be warmer than normal for India,

Bangladesh and Myanmar during all the four months and normal to cooler than normal for

Pakistan, Afghanistan Bhutan, Nepal and Sri Lanka, & normal to warmer than normal for remaining

countries. For Bhutan cooler than normal temperature anomaly in likely in August and September.

1. Important Global Climate Factors

1.1 Sea Surface Temperatures over the Pacific Ocean

The monthly mean Sea Surface Temperature (SST) anomalies (Fig.1) for May shows warm positive SST anomalies (>10C) along the equatorial Pacific with warmest anomalies (>20C) in the Eastern Pacific off the South American coast. Warm SST anomalies were also observed over northeast Pacific with anomalies >10C along the west coast off North American continent. However, cool SST anomalies were observed over west and central parts of subtropical North Pacific Ocean. In May, warm SST anomalies were observed over all the Niño regions (Fig.2). As per these observations, El Niño conditions of moderate strength are prevailing. The latest forecast from the coupled model indicate warming of SSTs is likely over all the Niño regions during the next 9 months, leading to moderate to strong El Niño conditions to set up during the Northern Hemisphere summer monsoon season and continue till the end of the year.

Fig. 1: Average SST anomalies (0C) for May 2015. (Data source: INCOIS-GODAS).

Fig.3: The time series of the monthly Dipole Mode Index (DMI) representing Indian Ocean Dipole (IOD). Observed anomaly for the last 4 months (Source: INCOIS-GODAS) and IITM-CFS model forecast anomaly for the next 9 months.

Fig.2: Time series of monthly area-

averaged SST anomalies (°C) in the 4 Niño regions. Observed anomaly for the last 4 months (Source: INCOIS-GODAS) and IITM-CFS model forecast anomaly for the next 9 months.

1.2 Sea Surface Temperatures over Indian Ocean

During May, positive SST anomalies were observed over most areas of Indian Ocean region (Fig.1). Warm SST anomalies (>10C) were seen over central southern Subtropical Indian Ocean and southwest off Australian coast. The Dipole Mode Index during May suggests prevailing Indian Ocean Dipole (IOD) conditions are neutral but in the positive side of the neutral range. The latest forecast (Fig.3) from the coupled model indicates neutral IOD conditions to continue till end of the year.

Fig. 4: Convection (OLR) Anomaly (W/m2) Pattern over the Asia Pacific Region for May

2015 (Data source: NCEP-NOAA)

1.3 Convection (OLR) Anomaly Pattern over the Asia Pacific Region:

The convective activity in terms of outgoing long wave radiation (OLR) anomalies for

May 2015 is shown in Fig.4. Slightly positive OLR anomalies (supressed convection, red shading) were observed over most parts of southern Pacific Ocean, North-eastern Australia, over maritime continents and subtropical northwest Pacific west of date line. On the other hand, negative OLR anomalies (enhanced convection, blue shading) were observed over Indian land mass, some parts of central south equatorial Indian Ocean, Australian land mass, whole of equatorial Pacific extending from about 160E to 80W. Negative OLR anomalies were also seen over Africa and North American land mass.

1.4 Snow Cover Area over the Northern Hemisphere (NH):

The May NH snow cover area (17.00 million sq. Km) was less than the 1981-2010

normal by 2017 thousand Sq. km and is 6th lowest snow cover extent during the last 49

years. Eurasian Snow cover in May was 8.93 million Sq. Km with negative departure of 790

thousand Sq. km than compared to the 1981-2010 normal and 12th lowest during the last 49

years. North America recorded snow cover area (80.70 million sq. Km) with a negative

departure of 1226 thousand Sq. km from normal and Canada recorded near normal snow

cover.

1.5. Madden Julian Oscillation (MJO):

During the early part of May, MJO was active with weak amplitude over Maritime

continents (phase 5). Subsequently MJO propagated eastward through phases 6, 7 and 8

with weak magnitude. In the end of May month, MJO was strengthened and in phase 1 over

Western hemisphere and Africa.

2. Seasonal Outlook for South Asia

The outlook was prepared based on the forecast from the India Meteorological

Department (IMD)’s seasonal forecast model (SFM). The model is a hydrostatic global

spectral model with a triangular truncation of 62 (T62) spherical harmonics (horizontal

resolution of about 250 km) and a vertical sigma coordinate system of 28 layers. The

ensemble simulations were carried out for 31 year period from 1982 to 2012 to prepare the

model climatology. Each forecast was initialized using atmospheric conditions for first 10

days of June, and run continuously for next five months. The forecasted SSTs from the

Coupled model, NCEP Climate Forecast System version 2 (CFSv2) were used as the

boundary conditions.

2.1. Precipitation Anomaly:

The seasonal forecasts for precipitation anomalies for the seasons July to October

(JAS) 2015 and August to October (ASO) 2015 are given in the Figures 5a and 5b

respectively. The JAS precipitation anomaly forecast indicates wetter than normal

precipitation over South Myanmar, Sri Lanka, Nepal, Bhutan, North-eastern part of Pakistan,

east central India (mainly over Odisha) and over Bay of Bengal. The JAS precipitation is

likely to be drier than normal over North-eastern India, Bangladesh, central and northern

Myanmar, Afghanistan and South Pakistan (Fig.5a). The remaining areas are likely to be

normal. The ASO precipitation anomaly forecast indicates pattern nearly similar to that

forecasted for JAS (Fig.5b).

2.2. Temperature Anomaly:

The temperature anomaly forecast for 2015 JAS season (Fig.6a) indicate normal to

above normal temperatures likely over Afghanistan & neighbouring Pakistan, whole of India,

Bangladesh, Bhutan, Myanmar and Sri Lanka with maximum temperature anomaly is

observed over some parts of Central and northwest India and over Northern Afghanistan and

Pakistan. Northern Nepal shows near normal temperatures anomaly. During ASO season

(Fig.6b), the temperature anomaly conditions are likely to be nearly similar to that of JAS

season except for smaller part of northern India, South and Central Karnataka of India,

Afghanistan and neighbouring Pakistan where normal to cooler than normal temperature

anomalies are likely.

a) b)

Fig.5: Seasonal forecasts of precipitation anomalies (mm/day) for (a) JAS and (b) ASO

(right) based on Initial conditions of June 2015.

(a) (b)

Fig. 6: Seasonal temperature anomalies (0C) for (a) JAS and (b) ASO (right) based on Initial

conditions of June 2015.

3 Forecast Outlook for the Country Averaged Monthly Precipitation and

Temperature

The model forecast for monthly precipitation and temperature for the next four months

(from July to October) averaged over the 8 south Asian countries viz., Afghanistan,

Bangladesh, Bhutan, India, Myanmar, Nepal, Pakistan and Sri Lanka is shown in the Figures

7 & 8 respectively. The monthly rainfall anomaly is expressed as percentage departure from

long period model average (LPMA) and monthly temperature anomaly is expressed in

degree Celsius.

In July, the country averaged monthly precipitation is likely to be wetter than normal

for Bhutan and Nepal and drier than normal for Afghanistan, Bangladesh, Myanmar,

Pakistan and Sri Lanka, and near normal for India (Fig 7). In August, the country averaged

precipitation is likely to be drier than normal for Afghanistan, Bangladesh, Bhutan, Myanmar

and Pakistan. Nepal and India shows near normal precipitation departure. For September

month, the monthly precipitation is likely to be wetter than normal for Afghanistan, India,

Nepal, Pakistan and Sri Lanka while normal precipitation is likely over Bangladesh and

Myanmar. For October, all countries show wetter than normal precipitation departure.

In July, the country averaged monthly temperature is likely to be warmer than normal

for Afghanistan, India, Myanmar, Pakistan and Sri Lanka and normal for Bhutan and

Bangladesh and Nepal (Fig 8). In August, the country averaged monthly temperature is likely

to be warmer than normal for Afghanistan, Bangladesh and India, and normal for Bhutan,

Nepal, Pakistan and Sri Lanka. In September, the country averaged monthly temperature is

likely to be warmer than normal for Bangladesh, Myanmar and Sri Lanka, and normal for

Afghanistan, Bhutan, India, Nepal and Pakistan. In October, the country averaged monthly

temperature is likely to be warmer than normal for Bangladesh, India, Myanmar and Sri

Lanka and cooler than normal to normal for Afghanistan, Nepal and Pakistan. Thus monthly

temperatures is likely to be warmer than normal for Bangladesh, India and Myanmar during

all the four months and normal to warmer than normal for rest of the other countries.

JULY AUG SEPT OCT JULY AUG SEPT OCT

Fig.7: Monthly rainfall Averaged over

south Asian countries expressed as

percentage departures (%) during

July to October, 2015.

Fig.8: Monthly temperature anomaly (°C)

averaged over south Asian countries

during July to October, 2015.