1. Forecast Outlook for the
2017 NE Monsoon Season Rainfall over South Peninsula, India 1

2. Climatology - NE Monsoon Rainfall
Sub Division
Season (Oct-Dec)
Rainfall (in mm)
Coefficient of Variation (CV)
(%)
Percent of Annual total (%)
Tamil Nadu
438.2
31.5
47.92
Rayalaseema
219.2
37.8
31.04
Coastal Andhra Pradesh
327.4
38.7
31.97
South Interior Karnataka
209.6
38.4
20.57
Kerala
480.7
28.8
16.44
South Peninsula
332.1
25.3
29.88

3. Verification of 2016 OND Outlook for India

4. Some Climatological Features of NE Monsoon Rainfall

5. OND Rainfall Vs ENSO South Peninsula Tamil Nadu El Nino La Nina
Rainfall Category
El Nino
LaNina
Below Normal ( <89)
8(28%)
9(38%)
Normal (>= 89 TO <=111)
10(34%)
11(46%)
Above Normal (>111)
11(38%)
4(17%)
El Nino
La Nina
Tamil Nadu
Rainfall Category
El Nino
LaNina
Below Normal ( <88)
6(21%)
10(42%)
Normal (>= 88 TO <=112)
13(45%)
9(38%)
Above Normal (>112)
10(34%)
5(21%)

6. LARGE SCALE INFLUENCES 2. INDIAN OCEAN DIPOLE (IOD)
SST anomalies are shaded (red color is for warm anomalies and blue is for cold). White patches indicate increased convective activities and arrows indicate anomalous wind directions during IOD events.

7. LARGE SCALE INFLUENCES 2. INDIAN OCEAN DIPOLE (IOD)
Western Block
Eastern Block
IOD: SST(Western Block)-SST(Eastern Block) +ve IOD good NEM activity -ve IOD suppressed NEM
Kripalani and Pankajkumar, 2004

8. CYCLONES AND DEPRESSIONS – SEASONAL CLIMATOLOGY
MAM JF
OND –
Many C&Ds cross coast
over NEM area;
Some recurve NE-wards
JJAS
Source: Cyclone eAtlas – IMD 

9. Tracks of tropical cyclones – El-Nino vs La-Nina
El Nino (1970 onwards; 8 years – Nov-1972,77,82,87,91,94,97,2002)
La Nina (1970 onwards; 6 years-
Nov- 1970,73,75,88,98,2000)
More northward moving cyclones that sweep away moisture from S to N latitudes leading to suppressed NEM activity over southern India
More westward tracks;
Good TC activity over AS.

10. NEM RAINFALL DUE TO CYCLONES AND DEPRESSIONS
11% of NEM seasonal rainfall variation is due to rainfall associated with passage of C&Ds
When C&DS cross TN / AP coasts, good rainfall over NEM region except over extreme southern parts and SL.
When C&Ds cross N or S of TN-AP coasts, poor rainfall over NEM region except over extreme southern parts and SL.
(Geetha and Raj, 2014)

11. Statistical Prediction System for NEM Rainfall over South India & Tamil Nadu
Geographical locations of the predictors used for 5-Parameter PCR model for south Peninsula
Geographical locations of the predictors used for 4-Parameter model for Tamil Nadu.

12. Models used & Forecasts
5-P principal component regression (PCR) model for probabilistic forecast of NE monsoon rainfall over south Peninsula.
Normal rainfall is most likely over south Peninsula
A 4-P PCR Model for probabilistic forecast of NE monsoon rainfall over Tamil Nadu.
Probabilities of all the tercile categories are close to climatological values with normal category having the highest probability.
Category
Rainfall Range (% of LPA)
Forecast Probability (%)
Below Normal
<89 28
Normal 39
Above Normal
>111 34
Category
Rainfall Range (% of LPA)
Forecast Probability (%)
Below Normal
<88 30
Normal 36
Above Normal
>112 34
5/23/2018

13. Monsoon Mission CFS (MMCFS)
South Peninsula
Initial Condition pertaining To
Skill score of ( )
C.C
Forecast for 2017
(% of LPA)
July
-0.43
7.0
August
-0.10 10
September
-0.06
Tamil Nadu
Initial Condition pertaining To
Skill score of ( )
C.C
Forecast for 2017
(% of LPA)
July
-0.21 -9
August
0.21 2
September
0.10 3

14. MME Forecast from Other Centers

15. Temperature Forecast

16. MMCFS T2mForecast: OND 2017
Normal to Above normal temperatures most parts of the country

17. NCEP CFS2 T2m Forecast
Below normal to normal temperatures along the Himalayas and over southeast Peninsular India. Above normal temperatures over the remaining areas

18. Cyclogenisis in North Indian Ocean
S.No
Classification of Cyclonic activity
Criterion 1.
Below Normal CA
No. of CD days: less than10 2.
Normal CA
No. of CD days: 3.
Above Normal CA
No. of CD days: greater than16
The atmospheric parameters considered as predictors (Source RMC, Chennai)
Based on MR and PCR (deterministic and probabilistic) model inputs, cyclonic activity (in terms of number of days of cyclonic disturbance) over the North Indian Ocean during October-December 2017 is expected to be Normal (10-16 CD days).
S.N
Parameter
Region
Period
CC with CD days (OND) 1
Outgoing Longwave Radiation (OLR)
90-110˚E & ˚S
July-Aug
-0.62** 2
Zonal wind at 850hPa (U850)
80-90˚E &10-15˚N
-0.53** 3
Zonal wind at 500hPa (U500)
95-105˚E &5-10˚N
-0.51** 4
Zonal wind at 200hPa (U200)
20-50˚E &Eq-10˚S
-0.54** 5
Meridional wind at 850hPa (V850)
˚E &10-15˚S
-0.60** 6
Meridional wind at 500hPa (V500)
75-80˚E &10-20˚N
+0.53** 7
Meridional wind at 200hPa (V200a)
˚E &25-30˚N
-0.55** 8
Meridional wind at 200hPa (V200b)
95-100˚E &5-10˚N
+0.48**

19. Summary of 2017 NE Monsoon Rainfall over India
IMD operational forecast for the 2017 North-east monsoon season (October-December) rainfall over south Peninsula (Tamil Nadu, Coastal Andhra Pradesh, Rayalaseema, Kerala and South Interior Karnataka) is most likely to be normal (89% -111% of LPA). The long period average (LPA) of the North-east monsoon season rainfall over the south Peninsula for the base period is mm.
The 2017 North-east monsoon season rainfall over Tamil Nadu is most likely to be normal (88%-112% of LPA). The long period average (LPA) of the North-east monsoon season rainfall over the Tamil Nadu for the base period is 438.2mm.
The mean 2m temperatures over most parts of the country is likely to be normal to above normal.

20. Thanks