The
India Meteorological Department (IMD), Ministry of Earth Sciences, issues the operational
long range forecasts for the southwest monsoon season (June-September) rainfall over the country as a whole in two stages i.e. in April and in June. The update for the forecast for the seasonal
rainfall over the country as a whole, issued in April, was released today. The Forecast predicts rainfall
over the country as a whole, for the 2016 southwest monsoon season (June to September), is most likely to be Above Normal
(>104% to 110%
of long period
average (LPA)).
The
forecasts for the monthly rainfall for July & August over the country as a
whole and for the season rainfall for the 4 broad geographical regions of India
(NW India, NE India, Central India
and South Peninsula)
have been issued
using a 6-parameter Ensemble Forecasting
System.
The
6 predictors used are:
North East Pacific
to North West Atlantic SST Anomaly Gradient (December + January), Southeast Equatorial Indian
Ocean Sea Surface Temperature (February), East Asia Mean Sea Level Pressure (February + March), Central Pacific (Nino 3.4)
Sea Surface
Temperature (March to May + tendency between March to May
& December to February), North Atlantic Mean Sea Level
Pressure (May) and North-Central
Pacific 850 zonal wind gradient (May).
Recent
changes in the atmospheric conditions over the Pacific reflect the weakening El
Niño conditions.
Latest forecast from
IMD-IITM (Indian Institute of Tropical Meteorology) coupled model indicate ENSO (El Niño - Southern Oscillations) neutral conditions are likely to continue and turn
to weak La Nina conditions in the latter part of the monsoon season. The rapidly declining El Nino
conditions became moderate in early April 2016, weak in early May and now have
turned to neutral ENSO conditions.
Over
Indian Ocean, the sea surface temperatures are warmer than normal over most
parts except along the coast off central and south Africa. The latest forecast from IMD-IITM coupled model indicates positive Indian Ocean
Dipole (IOD) conditions are most likely during early part of the
monsoon season and same to turn to negative IOD during the latter part of the
monsoon season.
The Monsoon
Mission Experimental forecast, based on the ESSO-IMD-IITM coupled dynamical model,
suggests that the monsoon rainfall during the 2016 monsoon season (June to September) averaged over the country as a
whole is likely to be 112% ±
5% of
long period model average (LPMA). The
experimental five category probability forecasts for the 2016 monsoon season
rainfall over the country as a whole using the experimental dynamical
prediction system are 0% (deficient),
0% (below
normal), 18% (normal),
18% (above normal) and
64% (excess).
The details of the Second Stage Forecasts for 2016 Southwest
Monsoon Rainfall are as follows:
Quantitatively,
the season rainfall for the country as a whole is likely to be 106% of the long period average (LPA) with a model error of ±4%. The LPA rainfall over the country as a whole for the
period 1951-2000 is 89 cm. Thus there is no change in the
updated quantitative forecast from the first stage operational forecast issued
on 12th April, 2016.
The
5 category probability forecasts for the Season (June to September) rainfall over the country as a whole is given below.
|
Category
|
Rainfall Range
(% of LPA)
|
Forecast Probability (%)
|
Climatological
Probability (%)
|
|
Deficient
|
< 90
|
0
|
16
|
|
Below
Normal
|
90 - 96
|
4
|
17
|
|
Normal
|
96 -104
|
33
|
33
|
|
Above
Normal
|
104 -110
|
40
|
16
|
|
Excess
|
> 110
|
23
|
17
|
The
season rainfall over Broad Geographical Regions is likely to be 108% of LPA over North-West India, 113% of LPA over Central India, 113% of LPA over South Peninsula, and
94%
of LPA over North-East India all with a model error
of ± 8 %.
The
rainfall over the country as a whole is likely to be 107% of its LPA during July and 104% of LPA during August both with a
model error of ± 9 %.
******
RDS/VM
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