Government of India Earth System Science Organisation

Ministry of Earth Sciences India Meteorological Department

REGIONAL REPORT ON SOUTHWEST MONSOON – 2017 OVER THE SOUTHERN PENINSULAR INDIA

(Prepared by: S.Balachandran, B.Geetha, D.Maragathavel, S.B.Thampi

Y.K.Reddy, S.Sudevan and S.M.Metri)

Regional Meteorological Centre

6, College Road, Chennai 600 006.

1

HIGHLIGHTS

During 2017, southwest monsoon (SWM) reached parts of southeast Bay of Bengal,

south Andaman Sea and Nicobar islands on 14th

May. It advanced over Kerala on

30th

May, 2 days prior the normal date of 1st June and covered the entire southern

peninsular India by 14th

June.

Rainfall during the SWM season of June-September, 2017 over the southern Indian

peninsular region comprising of the five states of Andhra Pradesh, Telangana, Karnataka,

Kerala and Tamil Nadu and two union territories of Puducherry and Lakshadweep was

717.6 mm which is 100% of its long period average (LPA) of 716.1 mm even though the

SWM seasonal rainfall over the country as a whole was 95% of its LPA.

Seasonal rainfall over the nine meteorological subdivisions covering the five states and

two union territories in the region, viz., Coastal Andhra Pradesh (CAP), Telangana

(TEL), Rayalaseema (RYS), Tamil Nadu &Puducherry (TN&PDC), Coastal Karnataka

(CK), North Interior Karnataka (NIK), South Interior Karnataka (SIK), Kerala

(KER),Lakshadweep(LAK) was normal to excess.

The seasonal rainfall figures over the nine subdivisions were15%,-13%, 27%, 29%, -

16%, 3%, 2%, -9%, and11% respectively. As such, seven meteorological subdivisions in

the region received normal rainfall (-19% to +19%) and twosubdivisions,RYS and

TN,received excess rainfall (≥+20%)of +27% and +29% of their respective LPAs (40 cm

and 32 cm respectively) during the season.

On the monthly scale, sub-divisional rainfall distribution was (i) normal to excess over 8

subdivisions and deficient over 1 subdivision in June (ii) deficient over 1 subdivision and

normal over one subdivisionin July (iii) 3 subdivisions recorded excess rainfall and the

other five came under normal category in August and (iv) 6 subdivisions received excess

rainfall, 2-normal, and 1-deficient in September.

Excess rainfall of about 60% or more were realised over TN and RYS in August (+82%

and +66% respectively) and over SIK (+81%) during September.

The SWM 2017 withdrew from the region on 26th

October 2017.

2

1. Onset and Advance

During the year 2017, the Bay of Bengal (BOB) branch of southwest monsoon (SWM)

current advanced into the BOB on 14th

May. The Arabian Sea branch of the SWM current, which

leads to the onset of SWM over Kerala, advanced over Kerala on 30th

May 2017, 2 days prior to

the normal date of onset over Kerala on 1st June. Subsequently, it advanced gradually into other

parts of India. It covered the entire southern peninsular India (SP) comprising of five states

(Andhra Pradesh, Telangana, Kerala, Karnataka and Tamil Nadu) and two union territories

(Puducherry and Lakshadweep) and divided into nine meteorological subdivisions of Coastal

Andhra Pradesh (CAP), Telangana (TEL), Rayalaseema (RYS), Tamil Nadu &Puducherry (TN),

Coastal Karnataka (CK),North Interior Karnataka (NIK), South Interior Karnataka (SIK), Kerala

(KER) and Lakshadweep (LAK) by 14th

June against the normal date of 10th

June. It covered the

states of Kerala and Tamil Nadu by 7th

June, RYS by 10th

, Karnataka and Telengana by 12th

and

Andhra Pradesh by 14th

June. As such, it took 16 days for the monsoon to cover the entire SP

region. Fig.1a depicts the progression of the northern limit of monsoon (NLM: A line

delineating the regions where the monsoon has advanced from the regions where the monsoon is

yet to set in) over the region and Fig.1b presents the INSAT-3D satellite imageries depicting the

onset of SWM over Kerala on 30th

May and its further advance into the SP region by 14th

June

2017. Fig.1c presents GPM satellite+ gauge merged rainfall depicting the advance of SWM

2017 over the SP region.

Fig.1a Advance of southwest monsoon 2017 over southern peninsular India depicted by

lines of northern limit of monsoon on various dates

3

Fig.1b INSAT-3D infra-red imageries as on 14th

, 26th

, 30th

&31th

/ 0300 UTC of May 2017

and 07th

/0300 UTC and 13th

/1200 UTC of Jun 2017 depicting the advance of SWM 2017

over the SP region

14-MAY-2017/0300 UTC

26-MAY-2017/0300 UTC

30-MAY-2017/0300 UTC

4

Fig.1b (contd….)

31-MAY-2017/0300 UTC

07-JUN-2017/0300 UTC

13-JUN-2017/1200 UTC

5

Fig.1c GPM satellite-Gauge merged 24-hr rainfall in cm as on 0300 UTC (0830 IST) of

02nd

, 07th

, 12th

and 13th

June 2017 depicting the advance of monsoon rains over the SP

region during SWM 2017

6

2. Rainfall distribution

2.1 Seasonal subdivisional rainfall

The SWM seasonal rainfall (June-September) during 2017 over the country as a whole

was 95% of its long period average (LPA) and that over the SP region was 100% of LPA.As per

IMD’s classification of monsoon performance over a meteorological subdivision, if the amount

of rainfall received over a region [expressed as percentage departure from normal (PDN)] is

between -19% and +19%, the monsoon performance is termedasnormal. If the PDN is between -

20% and -59%, the region comes under deficient category, if PDN is less than or equal to -60%,

the region falls under scanty category, PDN of +20% to +59% indicates excess rainfall category

and if the PDN is greater than or equal to +60%, it is termed as large excess. During SWM

2017, all the nine subdivisions in the SP region received normal to excess rainfall. Cumulative

seasonal (01st June to 30

th Sep) rainfall figures over the nine meteorological subdivisions of the

SP region are furnished in Table-1 and Fig.2.All the nine subdivisions in the region received

normal to excess rainfall during the season. Whereas TN and RYS received excess rainfall of

+29% and +27% respectively, the other seven subdivisions, viz., CAP, TEL, CK, SIK, NIK,

KER and LAK received normal rainfall during the season.

2.2 Monthly subdivisional rainfall

The monthly subdivisional rainfall scenario is presented in Table-2 and Fig.3. By and

large, rainfall over the subdivisions of the SP region has been normal to excess during the

months of June, August and September. But for SIK in June and TEL in September, all the

subdivisions received normal to excess rainfall during these months. In fact, largely excess

rainfall ( ≥+60%) was realized over TN (+82%) and RYS (+66%) in August and over SIK

(+81%) and KER (+78%) in September. But the July rainfall was deficient over eight out of nine

subdivisions in the region. Only CAP received normal rainfall during the month. The good

rainfall performance during August and September over the SP region is in contrast to the All

India monsoon scenario wherein only 87% and 88% of the respective monthly LPA was realized

during these months.

7

Table-1: Seasonal subdivisional rainfall distribution over the SP region during the SWM

season, 2017 (01st June-30 Sep 2017)

Largely

Deficient

Deficient Normal Excess Large

Excess

≤ -60% -20% to -59% -19% to +19% +20% to +59% ≥+60%

Fig.2 Subdivisionalseasonal rainfall (percentage departures from normal) during Jun-Sep

2017 over the SP region

SUB-DIVISION

Actual

rainfall

(mm)

Normal

rainfall

(mm)

Percentage

departure from

normal (%)

COASTAL ANDHRA PRADESH 669.6 581.1 15 TELANGANA 657.4 755.2 -13 RAYALASEEMA 506.1 398.3 27 TAMIL NADU & PUDUCHERRY 414.2 321.4 29 COASTAL KARNATAKA 2596.3 3083.8 -16 NORTH INTERIOR KARNATAKA 522.9 506 3 SOUTH INTERIOR KARNATAKA 670.5 660 2 KERALA 1855.9 2039.7 -9 LAKSHADWEEP 1108.3 998.5 11

8

Table-2: Monthly subdivisional rainfall performance during SWM 2017

ACL: Actual; NOR: Normal; PDN: Percentage Departures from Normal

Largely

Deficient

Deficient Normal Excess Large

Excess

≤ -60% -20% to -59% -19% to +19% +20% to +59% ≥+60%

Sub-division June July Aug Sep ACL

(mm)

NOR

(mm)

PDN

(%)

ACL

(mm)

NOR

(mm)

PDN

(%)

ACL

(mm)

NOR

(mm)

PDN

(%)

ACL

(mm)

NOR

(mm)

PDN

(%)

COASTAL

ANDHRA

PRADESH

152.3 103.9 47 154.6 160.4 -4 223.8 157.7 42 138.9 159.1 -13

TELANGANA

202.2 135.9 49 141.4 238.2 -41 200.7 218.8 -8 113.0 162.3 -30

RAYALASEEMA

88.9 67.7 31 52.2 94.2 -45 171.7 103.3 66 193.4 133.1 45

TAMIL NADU &

PUDUCHERRY 47.9 46.5 3 42.2 69.1 -39 161.6 88.7 82 162.5 117.0 39

COASTAL

KARNATAKA 831.4 867.3 -4 820.1 1159.7 -29 625.3 755.5 -17 319.6 300.9 6

NORTH

INTERIOR

KARNATAKA

131.1 104.7 25 76.8 135.0 -43 105.8 120.4 -12 209.3 146.0 43

SOUTH

INTERIOR

KARNATAKA

107.7 141.7 -24 125.6 216.1 -42 181.4 161.4 12 255.7 141.0 81

KERALA

579.8 649.8 -11 378.5 726.2 -48 462.6 419.3 10 435.0 244.3 78

LAKSHADWEEP

521.9 330.2 58 164.2 287.7 -43 206.2 217.5 -5 216.0 163.1 32

9

Largely

Deficient

Deficient Normal Excess Large

Excess

≤ -60% -20% to -59% -19% to +19% +20% to +59% ≥+60%

Fig.3 Monthly subdivisional rainfall distribution during Jun-Sep 2017

10

2.3 Weekly subdivisional rainfall progress

Week by week and cumulative weekly performance of SWM 2017 over the SP region are

presented in Table-3a and Table 3b respectively.

Table-3a: Week by week subdivisional rainfall during June-Sep 2017 over the SP region

Table-3a: Weekly cumulative subdivisional rainfall during Jun-Sep 2017

11

During the first four weeks of the season (1st-28

th June), rainfall activity was normal to large

excess over 5-7 subdivisions in the region. In the subsequent five weeks (29th

Jun-2nd

Aug), 5-8

subdivisions in the region, came under deficient to largely deficient categories. The week 17th

–

23rd

August, saw significant rainfall activity over the entire SP region with all the subdivisions in

the region recording normal to excess rainfall. During the following week (24th

-30th

Aug), except

TN and LAK all the other 7 subdivisions received excess to large excess rainfall (CAP, RYS,

CK, NIK, SIK& KER: large excess and TEL - excess). These two weeks rainfall activity brought

the subdivisions of Karnataka from deficient to normal category during the following week. The

subdivision of SIK recorded excess to large excess rainfall for about 7 weeks from 10th

August to

30th

September and RYS recorded excess to large excess rainfall continuously for 6 weeks from

10th

August to 20th

September.

2.4 Daily subdivisional rainfall and monsoon activity

Table-4a presents subdivision-wise daily spatial rainfall distribution over the SP region

during the SWM 2016 and Table-4b, the percentage frequency of various categories of spatial

rainfall distribution over each subdivision during the season. Widespread rainfall has been

realized on 76% of the days during the season over CK, on 62% of the days over KER and 50%

of the days over LAK. Fairly widespread to widespread rainfall activity has been realized over

SIK on 51% of the days. Scattered to widespread rainfall was realised for more than 60% of the

days over NIK, CAP and TEL. RYS and TN experienced scattered to widespread rainfall

activity on about 40% of the days during the season. Fig.4 presents daily cumulative rainfall over

the entire SP region during the SWM season, 2017 (01st June-30

th Sep).

12

Table-4a: Daily subdivisional rainfall distribution over the SP region during SWM 2017

Date

(ending

0830 IST) CAP TEL RYS TN CK NIK SIK KER LAK

1-Jun ISOL ISOL ISOL ISOL WD ISOL ISOL WD WD

2-Jun ISOL DRY DRY ISOL FWD ISOL ISOL WD WD

3-Jun ISOL ISOL SCT ISOL WD ISOL SCT WD WD

4-Jun ISOL FWD ISOL ISOL WD ISOL SCT WD WD

5-Jun ISOL ISOL ISOL ISOL FWD ISOL ISOL WD WD

6-Jun FWD ISOL ISOL SCT WD SCT SCT WD WD

7-Jun SCT FWD WD SCT WD WD FWD WD WD

8-Jun WD FWD ISOL ISOL WD ISOL SCT FWD SCT

9-Jun SCT SCT ISOL ISOL WD SCT SCT FWD FWD

10-Jun SCT SCT ISOL ISOL WD SCT FWD WD WD

11-Jun SCT SCT ISOL ISOL WD SCT FWD WD WD

12-Jun SCT FWD ISOL ISOL WD WD WD WD FWD

13-Jun SCT WD ISOL ISOL WD FWD WD WD WD

14-Jun SCT FWD ISOL ISOL WD ISOL FWD WD WD

15-Jun FWD ISOL SCT SCT WD SCT SCT FWD FWD

16-Jun WD FWD FWD ISOL WD WD SCT FWD FWD

17-Jun SCT ISOL FWD SCT WD SCT WD FWD SCT

18-Jun ISOL ISOL SCT ISOL WD FWD SCT SCT FWD

19-Jun FWD WD FWD ISOL WD FWD SCT FWD WD

20-Jun ISOL SCT SCT SCT FWD SCT SCT FWD WD

21-Jun SCT SCT ISOL ISOL WD ISOL FWD WD FWD

22-Jun SCT ISOL ISOL ISOL WD ISOL SCT WD SCT

23-Jun ISOL FWD ISOL ISOL WD ISOL SCT WD FWD

24-Jun SCT FWD FWD SCT WD SCT SCT WD WD

25-Jun WD SCT ISOL ISOL WD SCT SCT WD WD

26-Jun WD FWD ISOL ISOL WD SCT SCT WD WD

27-Jun FWD WD ISOL ISOL WD FWD SCT WD WD

28-Jun SCT FWD ISOL SCT WD SCT FWD WD WD

29-Jun SCT ISOL ISOL ISOL WD FWD FWD WD WD

30-Jun SCT SCT DRY ISOL WD SCT SCT WD FWD

1-Jul SCT FWD ISOL ISOL WD SCT SCT WD WD

2-Jul SCT ISOL ISOL ISOL WD SCT SCT WD WD

3-Jul SCT SCT ISOL ISOL WD ISOL SCT WD WD

4-Jul SCT ISOL ISOL ISOL WD SCT FWD WD WD

5-Jul ISOL ISOL DRY ISOL WD SCT FWD FWD WD

6-Jul ISOL SCT ISOL ISOL WD SCT SCT WD WD

7-Jul SCT SCT SCT SCT WD SCT SCT WD SCT

8-Jul SCT SCT SCT ISOL WD ISOL SCT WD FWD

9-Jul SCT ISOL ISOL ISOL WD SCT SCT WD WD

10-Jul ISOL SCT SCT ISOL FWD SCT ISOL WD WD

11-Jul SCT FWD ISOL ISOL WD SCT SCT WD WD

12-Jul FWD FWD FWD SCT WD FWD FWD FWD WD

13-Jul SCT FWD ISOL ISOL WD SCT FWD SCT FWD

14-Jul WD WD SCT ISOL WD FWD FWD WD FWD

15-Jul FWD FWD ISOL ISOL WD FWD FWD WD SCT

16-Jul FWD FWD SCT ISOL WD SCT FWD FWD FWD

17-Jul FWD WD ISOL ISOL WD SCT FWD WD DRY

18-Jul WD WD ISOL ISOL WD FWD FWD FWD FWD

19-Jul WD WD FWD ISOL WD WD WD WD WD

20-Jul SCT FWD ISOL ISOL WD WD WD WD DRY

21-Jul ISOL ISOL ISOL ISOL WD FWD FWD WD WD

22-Jul ISOL ISOL ISOL ISOL WD FWD FWD WD FWD

23-Jul DRY ISOL ISOL ISOL WD SCT SCT WD SCT

24-Jul SCT ISOL ISOL ISOL WD SCT SCT FWD SCT

25-Jul ISOL ISOL ISOL ISOL WD SCT FWD FWD FWD

26-Jul ISOL ISOL ISOL ISOL WD SCT SCT SCT DRY

27-Jul ISOL ISOL ISOL ISOL WD ISOL SCT FWD WD

28-Jul SCT SCT ISOL ISOL WD ISOL FWD WD WD

29-Jul SCT SCT ISOL SCT WD SCT SCT WD SCT

30-Jul ISOL ISOL ISOL ISOL WD SCT SCT ISOL FWD

31-Jul FWD ISOL FWD SCT WD ISOL SCT ISOL WD

13

Date

(ending

0830 IST) CAP TEL RYS TN CK NIK SIK KER LAK

1-Aug ISOL SCT ISOL SCT WD ISOL SCT FWD SCT

2-Aug SCT SCT ISOL FWD FWD ISOL ISOL SCT DRY

3-Aug SCT ISOL ISOL ISOL WD ISOL SCT FWD FWD

4-Aug SCT SCT ISOL ISOL WD FWD FWD WD WD

5-Aug SCT ISOL SCT ISOL WD SCT FWD WD WD

6-Aug SCT ISOL ISOL ISOL WD ISOL FWD WD FWD

7-Aug SCT ISOL SCT ISOL WD ISOL FWD WD WD

8-Aug SCT FWD ISOL SCT WD SCT SCT WD WD

9-Aug SCT FWD SCT FWD WD SCT SCT FWD FWD

10-Aug FWD FWD FWD FWD WD FWD FWD SCT WD

11-Aug ISOL SCT SCT SCT SCT SCT SCT FWD WD

12-Aug FWD SCT FWD SCT SCT SCT WD WD WD

13-Aug SCT SCT ISOL FWD ISOL SCT ISOL ISOL WD

14-Aug FWD WD ISOL SCT SCT ISOL ISOL ISOL DRY

15-Aug ISOL ISOL ISOL FWD ISOL ISOL SCT ISOL SCT

16-Aug SCT ISOL SCT SCT FWD FWD FWD WD FWD

17-Aug SCT ISOL SCT SCT WD SCT FWD FWD FWD

18-Aug WD SCT FWD SCT WD SCT WD WD WD

19-Aug WD WD SCT FWD WD FWD FWD WD WD

20-Aug WD WD FWD SCT WD WD WD WD FWD

21-Aug SCT SCT SCT SCT WD SCT WD WD WD

22-Aug SCT SCT FWD ISOL WD FWD FWD WD WD

23-Aug SCT SCT ISOL ISOL WD SCT FWD WD WD

24-Aug FWD ISOL WD SCT WD SCT FWD SCT SCT

25-Aug WD FWD WD SCT WD FWD WD SCT SCT

26-Aug FWD WD FWD ISOL WD WD FWD ISOL DRY

27-Aug SCT FWD FWD SCT WD WD WD WD WD

28-Aug FWD FWD SCT SCT WD WD WD WD WD

29-Aug WD WD SCT ISOL WD WD WD WD WD

30-Aug FWD FWD ISOL ISOL WD FWD FWD WD FWD

31-Aug SCT ISOL ISOL SCT FWD SCT SCT FWD SCT

1-Sep ISOL ISOL SCT SCT FWD SCT SCT SCT DRY

2-Sep SCT ISOL ISOL FWD ISOL ISOL SCT FWD DRY

3-Sep ISOL ISOL ISOL SCT ISOL ISOL SCT WD FWD

4-Sep ISOL SCT SCT ISOL ISOL ISOL ISOL SCT FWD

5-Sep SCT SCT FWD SCT ISOL SCT SCT WD DRY

6-Sep FWD SCT FWD FWD ISOL FWD FWD FWD WD

7-Sep SCT SCT WD SCT SCT FWD FWD SCT WD

8-Sep SCT SCT FWD SCT WD WD WD WD WD

9-Sep SCT ISOL ISOL FWD FWD SCT WD WD FWD

10-Sep ISOL ISOL ISOL SCT FWD SCT WD SCT WD

11-Sep SCT ISOL ISOL SCT FWD SCT FWD FWD WD

12-Sep ISOL ISOL ISOL ISOL FWD ISOL ISOL FWD WD

13-Sep SCT ISOL ISOL SCT WD SCT ISOL SCT FWD

14-Sep SCT FWD ISOL SCT FWD WD ISOL WD FWD

15-Sep FWD SCT WD ISOL FWD FWD FWD WD SCT

16-Sep ISOL SCT FWD ISOL WD WD SCT WD SCT

17-Sep FWD SCT WD FWD WD WD WD WD WD

18-Sep SCT FWD FWD FWD WD FWD WD WD WD

19-Sep ISOL ISOL ISOL ISOL WD SCT FWD WD FWD

20-Sep ISOL ISOL DRY ISOL WD FWD SCT WD WD

21-Sep ISOL ISOL DRY ISOL WD SCT ISOL WD WD

22-Sep ISOL ISOL ISOL ISOL WD ISOL SCT WD DRY

23-Sep ISOL ISOL DRY ISOL ISOL ISOL ISOL ISOL DRY

24-Sep SCT ISOL ISOL ISOL ISOL SCT ISOL ISOL FWD

25-Sep SCT ISOL FWD FWD SCT FWD WD ISOL FWD

26-Sep FWD SCT FWD SCT WD FWD WD SCT FWD

27-Sep FWD ISOL FWD SCT WD WD WD WD FWD

28-Sep WD FWD FWD SCT WD FWD WD WD WD

29-Sep SCT SCT FWD SCT WD WD WD WD FWD

30-Sep SCT SCT SCT ISOL FWD WD WD WD SCT

14

Table-4b: Percentage frequency of various categories of daily spatial rainfall distribution

over the subdivisions of the SP region during SWM 2017

Category

Frequency (%)

CAP TEL RYS TN CK NIK SIK KER LAK

WD 11 10 5 0 76 14 20 62 50

FWD 17 22 20 10 12 21 31 20 28

SCT 46 29 18 32 4 42 37 11 13

ISOL 25 39 52 58 7 23 11 7 0

DRY 1 1 5 0 0 0 1 0 9

WD: Widespread; FWD: Fairly Widespread; SCT: Scattered; ISOL: Isolated; DRY: No rain (Note:Kindly refer Appendix(i) for explanations on categorization of spatial rainfall distribution)

Fig.4 Daily cumulative rainfall over southern peninsular region during SWM season, 2017

Table-5 presents the seasonal frequency of active and vigorous monsoon conditions over

the various subdivisions of the SP region during SWM 2017. KER and RYS experienced more

than 25 days (27 and 26 days respectively) of active to vigorous monsoon activity during the

season. 20-25 days of active to vigorous monsoon conditions prevailed over CAP, TEL, NIK and

SIK and CK experienced 18 days of active to vigorous monsoon conditions during the season.

Whereas LAK experienced 3 days of active to vigorous monsoon conditions during June, TN

experienced 10 days of active to vigorous monsoon conditions during August-September.

15

Table-5: Subdivision-wise frequency of Vigorousand Active monsoon conditions over the

SP region during SWM 2017

Subdivision

JUN JUL AUG SEP Jun-Sep

VIG ACT VIG ACT VIG ACT VIG ACT VIG ACT

COASTAL ANDHRA PRADESH 5 1 3 2 7 0 4 3 19

TELANGANA 4 7 4 1 5 0 2 5 18

RAYALASEEMA 3 2 3 3 4 2 9 8 18

TAMIL NADU & PUDUCHERRY 5 1 2 2 7 3

COASTAL KARNATAKA 0 5 0 2 1 6 1 3 2 16

NORTH INTERIOR KARNATAKA 0 5 0 2 0 6 2 5 2 18

SOUTH INTERIOR KARNATAKA 2 1 0 2 0 7 4 6 6 16

KERALA 0 5 0 0 1 10 3 8 4 23

LAKSHADWEEP 1 2 0 0 0 0 0 0 1 2 VIG: Vigorous monsoon conditions (FWD to WD rainfall over the subdivision with rainfall amount more than 4

times the normal and at least 2 stations reporting 8 cm or more along the west coast or 5 cm or more else where).

ACT: Active monsoon conditions (FWD to WD rainfall over the subdivision with rainfall amount 1½ to 4 times the

normal and at least 2 stations reporting 5 cm or more along the west coast or 3 cm or more else where)

2.6 District-wise seasonal and monthly rainfall distribution

Fig.5a presents the district-wise seasonal rainfall as percentage departures from normal over the

various states and UTs over the SP region. Of the 102 districts in the SP region [Andhra Pradesh:

13 (CAP-9 & RYS-4), Telangana: 10, TamilNadu and Puducherry: 34 (34 and 2 respectively),

Karnataka: 30 (CK-3, NIK-11 & SIK-16), Kerala and Lakshadweep: 15 (14 and 1 respectively)],

95 districts received normal to above normal rainfall during the season. Five districts in Tamil

Nadu [Coimbatore (+169%), Theni (+131%), Tiruppur (+100%), Perambalur (+90%) and

Sivaganga (+75%)] and one in Karnataka (Mandya: +86%) came under large excess category at

the end of the season. Whereas all the districts in Andhra Pradesh, Tamil Nadu and Puducherry

received normal to above normal rainfall, 3 districts in Telangana (Adilabad, Nizamabad and

Karimnagar), 3 in Karnataka [Dakshina Kannada (CK), Chikkamagaluru (SIK) and Dharwad

(NIK] and one in Kerala (Wayanad) ended up deficient.

16

Fig.5a District-wise seasonal rainfall (percentage departure from normal) over various

states and union territories in the SP region

17

Fig.5a contd.

Fig.5b District rainfall performance over the entire SP region

18

Fig.5c (i) District-wise, monthly rainfall distribution over Andhra Pradesh (CAP & RYS)

during Jun-Sep 2017

19

Fig.5c (ii) District-wise, monthly rainfall distribution over Telangana during Jun-Sep 2017

20

Fig.5c (iii) District-wise, monthly rainfall distribution over Karnataka (CK, NIK & SIK)

during Jun-Sep 2017

21

Fig.5c (iv) District-wise, monthly rainfall distribution over Kerala and Lakshadweep

during Jun-Sep 2017

22

Fig.5c (v) District-wise, monthly rainfall distribution over Tamil Nadu and Puducherry

during Jun-Sep 2017

23

In the monthly scale, the following salient features are noted:

Andhra Pradesh (CAP & RYS): During June, except Vizianagaram which came under

deficient category (-22%), all other districts in CAP and RYS received normal to excess rainfall.

Large excess rainfall was realised over the districts of East Godavari (+89%), Guntur (+88%)

and Nellore (+71%). In July, Srikakulam and East Godavari districts received excess rainfall of

47% and 20% respectively. While West Godavari, Krishna, Guntur and Chittoor districts

received normal rainfall, all other districts ended up deficient with Kadapa recording largely

deficient rainfall of -61%. In August, excepting East Godavari, West Godavari and Krishna

which received normal rainfall, all other districts reported excess to large excess rainfall with

Nellore and Kadapa recording (+107% each) and Chittoor, Prakasam, Vizianagaram and

Srikakulam recording +70 to +90% during the month. In September, all districts in RYS received

excess rainfall with Chittoor coming under large excess category. In CAP, while Krishna, West

Godavari, Visakhapatnam and Srikakulam ended up deficient, all other districts received normal

to excess rainfall during the month.

Telangana: During June, all the ten districts in Telangana received excess to large excess

rainfall with Khammam, Mahabubnagar and Rangareddy districts reportinglarge excess rainfall

of +72%, +70% and +64% respectively. In July, excepting Khammam which came under normal

category (-19%), all other districts received deficient rainfall with Adilabad recording large

deficiency of -63%. In August, while Hyderabad recorded excess rainfall of +29%,Rangareddy,

Mahabubnagar and Karimnagar came under deficient category. Other districts received normal

rainfall during the month. In September, excepting Hyderabad, Mahabubnagar, Nalgonda and

Warangal which received normal rainfall, all otherdistricts ended up deficient with Nizamabad

recording large deficiency of -61%.

Karnataka: In June, 6 districts (Bidar, Kalaburgi, Vijayapura, Yadgir and Koppal in NIK and

Kolar in SIK) received excess to large excess rainfall. All three districts in CK (Uttar Kannada,

Udupi and Dakshina Kannada), Belagavi, Bagalkote and Raichur districts in NIK and

Shivamogga district in SIK received normal rainfall. All other districts came under deficient

category with Gadag, Bangalore-Rural and Chamrajnagar recordinglargely deficient rainfall. In

July, excepting Udupi (CK), Belagavi (NIK) and Chitradurga (SIK) which received normal

rainfall, all other districts ended up deficient with 5 districts in NIK and 4 districts in SIK

24

reporting largely deficient rainfall. In August, excepting Uttar Kannada (CK), Belagavi,

Dharwad, Haveri and Yadgir (NIK) and Shivamogga (SIK) which came under deficient category,

all other districts received normal to largeexcess rainfall [Large excess rainfall was realised over

Mandya (+174%), Mysuru (+140%), Ramanagara (+90%), Bangalore-Urban (+80%) and

Bangalore-Rural (+69%)]. In September all districts in SIK received excess to large excess

rainfall. While Shivamogga and Chikkamagaluru received excess rainfall, all other districts in

SIK received large excess rainfall. Mysuru (+166%), Mandya (+146%), Ramanagara (+119%),

Bangalore-Urban (+118%), Bangalore-Rural (+115%) and Davangere (+103%) received large

excess rainfall of more than +100%. In NIK, excepting Bidar which received deficient rainfall

and Kalaburgi&Vijayapura which received normal rainfall, all districts received excess to large

excess rainfall during the month. Haveri (+124%) and Belagavi (+109%) received large excess

rainfall of more than +100%. All three districts in the CK region received normal rainfall during

the month.

Kerala: In June, all districts in Kerala recorded normal rainfall excepting Idukki and Wayanad

districts which recorded deficient rainfall. July was a deficient month for all the districts in

Kerala with Wayanad, Idukki, Pathanamthitta, Kollam and Thiruvananthapuram recording

largely deficient rainfall. In August, all districts received normal to excess rainfall excepting

Wayanad which came under deficient category. September saw very good rainfall activity over

Kerala with all districts receiving excess rainfall. In fact 11 out of 14 districts recorded large

excess rainfall during the month.

Tamil Nadu & Puducherry: In June, most of the eastern coastal districts and adjoining areas

and the western districts of Coimbatore, Theni, Tirunelveli and Kanyakumari received normal to

large excess rainfall, but, the other interior districts ended up deficient to largely deficient. In

July, but for the extremely northern coastal districts and one or two interior districts (Coimbatore

and Sivaganga) all other districts (26 out of 34) came under deficient to largely deficient

category. However, August rainfall was beneficial to most of the districts. 30 out of 34 districts

recorded excess to large excess rainfall during the month. In September, the southern parts of

Tamil Nadu and the western districts of north Tamil Nadu received excess to large excess

rainfall, but, the northern coastal districts and some adjoining areas came under deficient to

normal category.

25

2.5 Heavy rainfall activity and extreme rainfall events

Table-6a presents the number of days of heavy rainfall occurrences (≥ 7 cm/day) over the

various subdivisions of the SP region during SWM 2017 and the month-wise frequencies are

presented in Table 6b.In the seasonal scale, SIK recorded 57 days of heavy rainfall events which

included 17 days of isolated very heavy rainfall occurrences with 3 days of extremely heavy

rainfall events (11th

June, 19th

July and 20th

July). CK and TN also recorded 2 days (11th

June

and 2nd

July) and one day (5th

Sep) of extremely heavy rainfall events respectively. In general,

CAP, TN, KER and CK recorded 50 or more days of heavy rainfall events. List of very heavy to

extremely heavy rainfall events is presented in Table 6c.

Highest rainfall of 29 cm/day has been recorded on 20th

July in Baghamandala in Kodagu

district of SIK followed by 27 cm/day at Ponnampet in the same district on the same day and at

Shirali in Uttara Kanada district of Coastal Karnataka on 11th

June.

Spatial distribution of very heavy to extremely heavy 24-hr rainfall that occurred on

11th

&19th

June, 5th

and 17th

Sep as depicted by IMD-NCMRWF GPM satellite-Gauge merged

rainfall is presented in Fig.6.

Table-6a: Subdivision-wise frequency of heavy rainfall days over the SP region during

1stJune-30

thSep 2017

Subdivision

No. of days of Heavy rainfall

(Rainfall ≥ 7 cm in 24 hrs)

Extremely

Heavy

(≥21 cm)

Very

Heavy

(≥12 cm)

Heavy

(≥7 cm) COASTAL ANDHRA PRADESH 0 7 56

TELANGANA 0 5 45

RAYALASEEMA 0 5 27

TAMIL NADU & PUDUCHERRY 1 15 54

COASTAL KARNATAKA 2 19 50

NORTH INTERIOR KARNATAKA 0 2 29

SOUTH INTERIOR KARNATAKA 3 17 57

KERALA 1 16 51

LAKSHADWEEP 0 1 7 Note: Kindly refer Appendix-(ii) for explanations on various terminologies used for description of rainfall intensity.

26

Table-6b: Month-wise frequency of heavy rainfall days during June-Sep 2017

ExH: Extremely Heavy (≥21 cm); VH: Very Heavy (≥12 cm); H: Heavy (≥7 cm)

Table-6c District-wise list of stations & dates of very heavy -extremely heavy rainfall

occurrences with rainfall amount during Jun-Sep 2017

District Date, Station and 24-hr accumulated rainfall (in cm) (ending 0830 IST of the specified date)

COASTAL ANDHRA PRADESH

Guntur Jun: 19th

: Atchampet-15

Krishna Aug: 10th

: Tiruvuru-13

Vizianagaram Jul: 11th

: Pusapatirega- 12

Aug: 12th

: Pusapatirega- 12; 28th

: Kurupam-16

West Godavari Sep: 17th

: Polavaram-13

Visakhapatnam Sep: 30th

: Narsipatnam-14

Srikakulam Aug: 28th

: Palasa- 12;

TELANGANA

Adilabad Jun: 11th

: Luxettipet-15, Boath-14;

Aug: 20th

: Mudhole-18

Mehabubnagar Jun: 19th

: Kundurg-18;

Khammam Jun: 19th

: Burgampadu-14, Mulakalapalle-12

Medak Aug: 20th

: Narayankhed-13

Nizamabad Jun: 16th

: Jukkal-12, Madnur-12

Aug: 20th

: Ranjal-19, Navipet-18, Nizamsagar& Kotgiri-17 each,

Varni& Yellareddy-16 each, Bodhan-15, Rudrur-13, Pitlam, Jukkal, Banswada &

Gandhari -12; 26th

: Machareddy & Sadasivanagar – 12 each;

Warangal Aug: 20th

: Nallabelly-19, Venkatapur-18, Shayampet-16, Atmakur-15,

Mulug&Govindaraopet – 14 each

Karimnagar Aug: 20th

: Sarangapur-17

Sub-division No. of days of Heavy rainfall(Rainfall ≥ 7 cm in 24 hrs)

June July Aug Sep ExH VH H ExH VH H ExH VH H ExH VH H

COASTAL ANDHRA

PRADESH 0 1 11 0 1 11 0 3 21 0 2 13

TELANGANA

0 3 15 0 0 6 0 2 11 0 0 13

RAYALASEEMA

0 0 4 0 0 2 0 2 8 0 3 13

TAMIL NADU &

PUDUCHERRY 0 4 9 0 2 8 0 5 18 1 4 19

COASTAL

KARNATAKA 1 6 16 1 6 12 0 5 13 0 2 9

NORTH INTERIOR

KARNATAKA 0 1 7 0 0 5 0 0 5 0 1 12

SOUTH INTERIOR

KARNATAKA 1 4 14 2 3 13 0 7 13 0 3 17

KERALA

0 6 15 0 2 7 0 3 14 1 5 15

LAKSHADWEEP

0 1 4 0 0 0 0 0 1 0 0 2

27

RAYALASEEMA

Chittoor Aug: 10th

: Chittoor- 13;

Sep: 09th

: Chittoor- 13.

Anantapur Sep: 10th

: Rolla- 12; 15th

: Setur- 13.

Kadapa Aug: 10th

: Royachoti-12; 25th

: Duvvur-15, Chapad-13

Kurnool Aug: 25th

: Owk- 20.

TAMIL NADU & PUDUCHERRY

Thanjavur Jun: 06th

: Papanasam-14;

Aug: 09th

: Pattukottai & Adirampatnam- 13 each; 10th

: Thanjavur-13;

Sep: 09th

: Kumbakonam-16

Sivaganga Jun: 15th

: Sivaganga-14

Coimbatore Jun: 27th

: Valparai(PTO) -17, Chinnakalar-14; 28th

: Chinnakalar-13;

Sep: 18th

: Chinnakalar & Valparai (PTO)- 17 each.

Nilgiris Jul: 20th

: Devala- 20, G.Bazar & Naduvattam – 19 each;

Sep: 11th

: Coonoor PTO – 12

Vilupuram Jul: 30th

: Tindivanam-12

Kancheepuram Aug: 2nd

: Madranthagam-15

Thiruchirappalli Aug: 2nd

: Pullambadi-14

Thiruvannamalai Aug: 2nd

: Chengam -13; 13th

: Polur-14

Madurai Aug: 2nd

: Vadipatti -12;

Sep: 2nd

: Peraiyur-12

Thiruvallur Aug: 19th

: Redhills-13

Dindigul Sep: 2nd

: Natham-17

Karur Sep: 2nd

: Karur-16, Aravakurichi-14

Vellore Sep: 2nd

: Alangayam-12

Theni Sep: 5th

: Uthamapalayam-24

Tiruppur Sep: 5th

: Kangeyam-12

COASTAL KARNATAKA

Dakshina Kannada June:11th

: Mangaluru AP- 15, Panambur, Mudubidre- 14;

12th

: Mulki&Mudubidre- 15 each; 26th

: Mani- 15, Mudubidre- 13, Puttur -12;

July:14th

: Mulki- 15;

Aug: 4th

: Bantwal- 16; 29th

: Sulya- 12;

Sep: 17th

: Mulki- 12.

Udupi June:11th

: Kundapur- 19, Siddapura ,Kollur& Kota- 16 each, Karkala- 14;

12th

: Kollur- 17, Kota- 12; 25th

: Kota &Kundapur- 13 each;

26th

: Kollur&Karkala- 15 each;

July:2nd

: Kollur- 25; 3rd

:Kollur- 16; 4th

: Kollur- 15; 14th

: Kota- 13;

19th

: Siddapura- 12.

Aug: 25th

: Siddapura- 13;

Sep: 28th

: Karkala- 15.

Uttara Kannada June: 6th

: Kumta- 14; 10th

: Honnavar- 15,Shirali- 14;

11th

:Shirali- 27, Kumta- 15, Honnavar- 14, Gersoppa- 13;

12th

: Kumta- 16, Gersoppa & Shirali- 15 each, Honnavar- 14;

July: 2nd

:Gersoppa- 13; 3rd

: Gersoppa- 12; 4th

: Honnavar- 13;

14th

: Shirali- 13; 19th

: Gersoppa & Siddapur – 12 each; 20th

: Kadra- 12.

Aug: 20th

: Manki- 12; 27th

: Gersoppa- 12;

NORTH INTERIOR KARNATAKA

Bidar June:13th

: Bidar- 13

Bagalkote Sep: 14th

: Kerur- 12.

28

SOUTH INTERIOR KARNATAKA

Kodagu June: 26th

: Bhagamandala- 12

July:19th

: Bhagamandala- 20;

20th

:Bhagamandala- 29, Ponnampet- 27, Virajpet- 15, Napoklu- 13, Madikeri- 12.

Aug: 29th

: Bhagamandala- 12.

Sep: 19th

: Bhagamandala- 12.

Shivamogga June:11th

:Agumbe- 23,Hosanagar- 18; 12th

: Hosanagar- 19,Agumbe- 12;

25th

: Agumbe- 13; 26th

: Agumbe- 15;

July:19th

: Agumbe- 15; Linganamakki- 12;

20th

: Agumbe- 20; Hosanagar- 16; 21st :Hosanagar- 21; Linganamakki- 12.

Aug:4th

: Agumbe- 15; 12th

: Agumbe- 16; 21st: Agumbe- 12; 27

th : Agumbe- 14

Chikkamagaluru June: 26th

: Sringeri, Kalasa – 12 each

July:19th

: Kottigehara- 15, Kammaradi-12;

20th

: Kottigehara- 21, Kammaradi- 14, Kalasa- 13.

Mysuru Aug: 10th

: T Narasipura- 12;

Sep: 6th

:Mysuru -12

Mandya Aug:15th

: Mandya -13;

Sep: 6th

: KR Sagara- 12.

Bengaluru U Aug:15th

: Bengaluru HAL AP- 14, Bengaluru City- 13

Davangere Sep:25th

: Davangere- 13

Ramnagara Sep:10th

: Magadi-14

KERALA

Kozhikode Jun:11th

: Vadakara- 18

Jul:2nd

: Vadakara – 12

Aug:5th

: Vadakara – 14

Sep: 17th

: Vadakara - 18

Kasaragod Jun: 12th

: Kudlu- 12

Malappuram Jun: 24th

: Ponnani – 16, 27th

: Perinthalmanna – 12;

Sep: 11th

: Manjeri – 12, 14th

: Nilambur – 17;

17th

: Angadippuram – 19, Perinthalmanna – 16

Palakkad Jun: 27th

: Alathur – 12

Sep: 17th

: Mannarkkad – 23

Thrissur Jun: 26th

: Vadakkancherry – 15, Vellanikkara – 13;

Sep: 17th

: Vellanikkara&Kodungallur – 12 each

Wayanad Jun: 28th

: Vythiri – 15

Jul: 20th

: Vythiri – 13

Kottayam Aug: 11th

: Kottayam – 18

Kannur Aug: 29th

: Irikkur – 13

Alappuzha Sep: 6th

: Mavelikkara - 12; 18th

: Mavelikkara - 12

Idukki Sep: 14th

: Peermade – 17

Ernakulam Sep: 17th

: Piravom – 15, Perumbavur – 12

18th

: Ernakulam (South Railway) – 15

Pathanamthitta Sep: 17th: Konni – 12

LAKSHADWEEP

Lakshadweep Jun: 3rd

: Agathi – 12

29

Fig.6 GPMsatellite-Gauge merged rainfall in cm depicting very heavy(12-20 cm/day) to

extremelyheavy(≥ 21cm/day) rainfall at isolated places over CK on 11th

Jun, TEL on 19th

Jun, Tamil Nadu on 5th

Sep and Kerala on 5th

and 17th

Sep 2017.

30

2.6 Dry and Wet conditions

Based on Standardized Precipitation Index (SPI), a widely accepted index based on

rainfall used for drought monitoring world-wide, moderately/severely/extremely dry or wet

situations over various districts of the region during June-Sep 2017 are depicted in Fig.7. The

SPI indicates wet conditions over all districts of CAP, RYS and TN and parts of SIK, NIK and

TEL at the end of the season. Most districts of CK and KER ended up mildly-moderately dry.

Fig.7 Standardised Precipitation Index (SPI) over the SP region during Jun-Sep 2017

2.7 Chief synoptic features

Onset phase: Under the influence of an upper air trough from NIK to South TN extending upto

0.9 kma.s.l on 25th

and 26th

May and an off-shore trough from North Maharashtra coast to North

Kerala coast on 30th

May which extended from South Maharashtra coast to North Kerala on 31st

May, onset of SWM 2017 took place on 30th

May.

Monthly features: Fig.8 depicts the 850, 500 and 250 hPa wind anomaly during the months of

June, July August and September 2017.

In June, at 850 hPa level an anomalous cyclonic circulation over southwest Arabian Sea

and anomalous easterlies were observed. At 500 hPa level, an anomalous anticyclonic circulation

was observed over the northwestern region and adjoining areas. At 250 hPa level an anomalous

anticyclonic circulation was observed over the northern and central parts of the country. Under

the influence of the Arabian Sea and the Bay of Bengal branches of the monsoon current during

31

the onset phase and its further advancement, good rainfall activity prevailed over the SP region

in June.

In July, at 850 hPa level, an anomalous cyclonic circulation /east west trough was

observed over the central parts of country. This anomalous circulation/trough extended upto 500

hPa level. At 250 hPa level, an anomalous anti-cyclonic circulation was observed over the

northern and northeastern parts of the country. Under active monsoon conditions over the central

and northern parts of India in association with advance of the monsoon current into these

regions, monsoon activity over the southern region was rather weak in July.

During August, at 850 hPa level, an anomalous north-south wind discontinuity over the

peninsular region and anomalous southerlies over the northeast region were observed. At 500

hPa level, anomalous westerlies were observed over the peninsula. At 250 hPa level, anomalous

ridge was observed over the eastern/northeastern region.

In September, at 850 hPa level, an anomalous cyclonic circulation /trough was observed

over the east Arabian Sea and adjoining Kerala coast. Anomalous easterlies /southeasterlies were

also observed over the samelevel. At 500 hPa level, an anomalous anticyclonic circulation was

observed over the peninsula and centralparts of the country. Thus anomalous anticyclonic

circulation was more marked at 250 hPa level.

Under break monsoon conditions on many days in August and September, troughs in the

monsoon westerlies and cyclonic circulations in the lower tropospheric levels over the peninsular

region led to good rainfall activity over the SP region.

In the daily scale, off-shore troughs at mean sea level along the west coast of peninsular

India, upper air cyclonic circulations over the various parts of the SP region and over Bay of

Bengal and neighbourhood, east-west shear zone in the lower-mid troposphere running along the

13-18°N latitudes, low pressure areas that formed over Westcentral and adjoining North Bay of

Bengal off Andhra Pradesh / South Odisha coast with their associated upper air cyclonic

circulation extending upto mid tropospheric levels tilting southwest-wards with height, troughs

on sea level chart that ran from CAP/TEL to Tamil Nadu / Comorin area across Rayalaseema

and interior Tamil Nadu and troughs in the monsoon westerlies in the lower tropospheric levels

were associated with rainfall activity over the SP region. Mean sea level pressure analysis based

on 10-06-2017/0300 UTC depicting an off-shore trough and a low pressure area over the

northern parts of central of Bay of Bengal is shown Fig.9a.

32

Fig.8: 850hPa, 500 hPa& 250 hPa wind anomalies over Indian region during SWM

2017(Source: Climate Diagnostic Bulletin of India, IMD Pune)

33

Fig.8 contd. …

34

(a)

(b)

Fig.9 (a) Mean sea level pressure analysis chart based on 10-06-2017/0300 UTC and (b)

upper air streamline analysis based on 09-08-2017/0000 UTC

35

Fairly widespread to widespread rainfall was realized in CK, KER, LAK and SIK on 11-

06-2017 with extremely heavy rainfall of 27 cm/day recorded at Shirali in CK. Upper air

streamline analysis based on 09-08-2017/0000 UTC indicating trough in monsoon westerlies and

cyclonic circulation affecting parts of SP region is shown in Fig.9b. Fairly widespread to

widespread rainfall activity was reported on 10-08-2017 in all the subdivisions in the region

except Kerala where scattered rainfall was realized.

3. Withdrawal of SWM 2017 from the SP region

Withdrawal of SWM 2017 from the SP region commenced on 17th

October over northern

parts of Telangana and gradually proceeded southwards. With the gradual setting in of

northeasterlies along the southeastern coastal areas, SWM withdrew from the entire country on

26th

October 2017. Fig.10 depicts gradual withdrawal of SWM 2017 from various parts of the SP

region.

Fig.10 Isolines of dates of withdrawal of SWM 2017 over the SP region

4. Summary

During 2017, southwest monsoon reached parts of southeast Bay of Bengal, south

Andaman Sea and Nicobar islands on 14th

May. It advanced over Kerala on 30th

May, 2 days

36

prior the normal date of 1st June and covered the entire southern peninsular India by 14

th June.

Rainfall during the SWM season of June-September 2017 over the southern Indian peninsular

region comprising of the five states of Andhra Pradesh, Telangana, Karnataka, Kerala and Tamil

Nadu and two union territories of Puducherry and Lakshadweep was 717.6 mm which is 100%

of its long period average (LPA) of 716.1 mm even though the SWM seasonal rainfall over the

country as a whole was 95% of its LPA. Seasonal rainfall over the nine meteorological

subdivisions covering the five states and two union territories in the region, was normal to

excess. The seasonal rainfall figures over the nine subdivisions CAP, RYS, TEL, TN, CK, NIK,

SIK, KER, LAK) were15%, -13%, 27%, 29%, -16%, 3%, 2%, -9%, and 11% respectively. On

the monthly scale, sub-divisional rainfall distribution was (i) normal to excess over 8

subdivisions and deficient over 1 subdivision in June (ii) deficient over 8 subdivisions and

normal over one subdivision in July (iii) 3 subdivisions recorded excess rainfall and the other

five came under normal category in August and (iv) 6 subdivisions received excess rainfall, 2-

normal, and 1-deficient in September. Excess rainfall of about 60% or more were realised over

TN and RYS in August (+82% and +66% respectively) and over SIK (+81%) during September.

The SWM 2017 withdrew from the region on 26th

October 2017.

Acknowledgements

This report is a compilation of real-time observational data and analytical products

generated by various IMD offices including IMD New Delhi, Pune, Hyderabad, Bangalore and

Thirvananthapuram as well as Raingauge networks of various state governments. Contribution

from all officials involved in generation of data and analytical products used for preparation of

this report is duly acknowledged.

37

APPENDIX-(i): Terminologies for Spatial rainfall distribution

WD - Widespread (Most places): 75 % or more number of stations of a region (sub-division)

reporting at least 2.5 mm rainfall.

FWD- Fairly widespread (Many places): 51% to 74 % number of stations of a region (sub-

division) reporting at least 2.5 mm rainfall.

SCT- Scattered (at a few places): 26 % to 50% number of stations of a region (sub-division)

reporting at least 2.5 mm rainfall.

ISOL- Isolated (At isolated places): 25% or less number of stations of a region (sub-division)

reporting at least 2.5 mm rainfall.

DRY: No station of a region reported rainfall

APPENDIX-(ii): Terminologies for description of intensity of rainfall