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

(May to August 2015)

Issued in April 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.

Currently warm ENSO neutral/ border line El Nino conditions are prevailing over equatorial Pacific

with sea surface temperatures across most of the equatorial pacific are warmer than normal. The

latest coupled model forecast suggest, the conditions to reach weak El Nino level and persist till

the end of the year.

The 2015 MJJ mean precipitation is likely to be wetter than normal over northern most areas of

India, south Myanmar, Sri Lanka, most areas of Nepal and Bhutan, some parts of Northeast India,

southern most Peninsular India and normal over remaining areas of the region. The 2015 JJA

mean precipitation is likely to be wetter than normal over northern most areas of India and

southern Myanmar. Drier than normal JJA precipitation is likely over some parts of southern

region, Sri Lanka and Bangladesh & normal over the remaining areas.

The 2015 MJJ mean temperatures are likely to be warmer than normal over Peninsular India,

extreme North India, neighbouring west of Pakistan, Afghanistan and some areas of eastern

Bangladesh & neighbouring Myanmar, cooler than normal over some areas of central Nepal and

normal over remaining areas. The JJA mean temperatures are likely to be nearly same as during

MJJ, except the warmer than normal temperature likely over some eastern parts of the region.

The country averaged monthly May precipitation likely to be drier than normal for Afghanistan and

normal to above normal over all the south Asian countries. Drier than normal is likely over

Bangladesh and Sri Lanka during all the last 3 months.

The country averaged monthly temperature during is likely to be cooler than normal for Nepal and

normal to warmer than normal for all the remaining countries during all the four months.

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 March show warm SST anomalies in the central Pacific around the date line. Warm SST anomalies were also observed over northeast Pacific with anomalies greater than 10C along the west coast off the North American continent. However, cool SST anomalies were observed over East and Central parts of subtropical South Pacific Ocean. In March, warm SST anomalies were observed over all the Nino regions except NINO1+2 (Fig.2). As per these observations, Warm ENSO neutral/ border line El Nino conditions are prevailing. The latest forecast from the coupled model indicate warming of SSTs is likely over all the Nino regions during the next 9 months, leading to weak El Nino conditions to set up during the Northern Hemisphere spring season and continue till the end of the year.

Fig. 1: Average SST anomalies (0C) for March 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 3 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 3 months (Source: INCOIS-GODAS) and IITM-CFS model forecast anomaly for the next 9 months.

1.2 Sea Surface Temperatures over Indian Ocean

During March, cool SST anomalies were observed over west equatorial Indian Ocean and north Arabian Sea and Bay of Bengal (Fig.1). Warm SST anomalies were also seen over Central and tropical Southeast Indian Ocean and northwest off Australian coast. The Dipole mode Index during March was slightly negative and its magnitude showed slight increase than that in February. The latest forecast (Fig.3) from the coupled model shows weakening of DMI in the next 9 months resulting near normal to negative Indian Ocean Dipole conditions to continue till the end of the year.

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

March 2015 is shown in Fig.4. Slightly positive OLR anomalies (supressed convection, red shading) were observed over west Equatorial Indian Ocean, maritime continent, northern Australia and equatorial east Pacific east of 150oW. On the other hand, negative OLR anomalies (enhanced convection blue shading) were observed over Indian land mass, southern part of Australia, equatorial central Pacific west of date line and over tropical east Pacific along the west coast off North America. Negative OLR anomalies were also seen over Arabian Sea.

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

March shows reduced snow cover over Northern Hemisphere and Eurasia. The NH

snow cover area (38.46 million sq. Km) was less than the 1981-2010 normal by 1670

thousand Sq. km and was 7th lowest in March during the last 49 years. Eurasian Snow cover

in March was 23.39 million Sq. Km with negative departure of 1093 thousand Sq. km than

compared to the 1981-2010 normal and 9th lowest during the last 49 years. North America

have normal snow cover with a slight negative departure of 576 and Canada showed

positive departure of 70 thousand Sq. km respectively when compared to the 1981-2010

normal.

1.5. Madden Julian Oscillation (MJO):

During the early part of March, MJO became active near east maritime continent

(phase 5). Subsequently MJO propagated eastward through phases 6 and 7 with high

magnitude over Western Pacific. In the early second half, MJO was in phase 8 and was

active over western Hemisphere and Africa moving to phase1 in the later part of March.

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 April, 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 May to July (MJJ)

2015 and June to August (JJA) 2015 are given in the Figures 5a and 5b respectively. The

MJJ precipitation anomaly forecast indicates wetter than normal precipitation over south

Myanmar, southern India, Bhutan, northern Bay of Bengal, northern most areas of India and

Sri Lanka. The MJJ precipitation is likely to be near normal over remaining parts of the

region (Fig.5a). The JJA precipitation anomaly forecast indicates normal precipitation over

Nepal, north of India and part of Pakistan and Afghanistan (Fig.5b). However, drier than

normal JJA precipitation is likely over northeast India, central to southern tip of India, Sri

Lanka and Bay of Bengal. Normal to wetter than normal precipitation is likely to be over

Maldives for MJJ and likely to be drier than normal for JJA.

2.2. Temperature Anomaly:

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

above normal temperatures are likely over Afghanistan & neighbouring Pakistan, some

areas of central India & Bangladesh and southern most parts of India & Sri Lanka. Below

normal temperatures are likely over some areas of central Nepal. The temperatures are

likely to be near normal over remaining areas of the region. During JJA season (Fig.6b),

conditions are likely to be nearly similar to that of MJJ season expect for warmer than normal

temperature conditions over more areas of east India and Sri Lanka.

a) b)

Fig.5: Seasonal forecasts of precipitation anomalies (mm/day) for (a) MJJ and (b) JJA (right) based on Initial conditions of April 2015.

(a) (b)

Fig. 6: Seasonal temperature anomalies (0C) for (a) MJJ and (b) JJA (right) based on Initial conditions of April 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 May to August) 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 May, the country averaged monthly precipitation is likely to be drier than normal

for Afghanistan, near normal for Pakistan and wetter than normal for the remaining countries

(Fig 7). In June, the monthly precipitation is likely to be drier than normal for Bangladesh,

wetter than normal for Pakistan and normal for the remaining countries. In July, the monthly

precipitation is likely to be drier than normal for Afghanistan and Sri Lanka, wetter than

normal for Nepal, and normal for other countries. In August, the forecast suggest drier than

normal for Bangladesh, Nepal and Sri Lanka, wetter than normal for Myanmar and normal

for all other countries. Nepal shows maximum positive precipitation percentage departure for

July month.

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

for Afghanistan and India, cooler than normal for Nepal, and near normal for all other

countries (Fig 8). In June, the country averaged monthly temperature is likely to be warmer

than normal for Afghanistan, Pakistan, India and Sri Lanka and normal to slightly warmer

than normal for Bangladesh. Nepal is likely to experience cooler than normal temperatures.

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

Afghanistan, Bangladesh, Pakistan and Sri Lanka, cooler than normal for Nepal and normal

for the remaining countries of the region. In August, the country averaged monthly

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

Lanka, and slightly warmer than normal for Pakistan. Nepal is likely to have cooler than

normal temperature. Thus monthly temperatures is likely to be cooler than normal for Nepal

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

MAY JUNE JULY AUG MAY JUNE JULY AUG

Fig.7: Monthly rainfall Averaged over

south Asian countries expressed as

percentage departures (%) during

May to August, 2015.

Fig.8: Monthly temperature anomaly (°C) averaged over south Asian countries during May to August, 2015.