Government of India Earth System Science Organisation

Ministry of Earth Sciences India Meteorological Department

REGIONAL REPORT ON SOUTHWEST MONSOON – 2016

OVER SOUTHERN PENINSULAR INDIA

(Prepared by: S.Balachandran, B.Geetha, R.Rajamohan and S.B.Thampi)

Regional Weather Forecasting Centre Office of the Deputy Director General of Meteorology

Regional Meteorological Centre, Chennai

1

HIGHLIGHTS

During 2016, onset of southwest monsoon (SWM) over Kerala took place on 8th

June, 7

days behind the normal schedule of 1st June and covered the entire southern peninsular

India by 19th

June.

Rainfall during the SWM season of June-September, 2016 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

92% of its long period average (LPA).

Seasonal rainfall over the nine meteorological subdivisions over 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) and were 14%, 19%,

-2%, -19%, -21%, 4%, -21%, -34% and -25% and respectively.

Five meteorological subdivisions in the region received normal rainfall (-19% to +19%)

and four subdivisions ended up deficient (≤-20%) at the end of the season. KER and CK

which receive about 200 cm and 300 cm of rainfall respectively during SWM came under

deficient category with -34% and -21% respectively.

On the monthly scale, sub-divisional rainfall distribution was (i) excess over 6

subdivisions and normal over 3 subdivisions in June (ii) 3 subdivisions received excess

rainfall, 3-normal and 3-deficient in July (iii) 8 subdivisions ended up deficient and 1-

scanty in August and (iv) 2 subdivisions received excess rainfall , 1-normal, 5-deficient

and 1-scanty in September.

Withdrawal of SWM 2016 from the region commenced on 15th

October. It withdrew from

the entire region on 28th

October 2016.

2

1. Onset and Advance

Normally, onset of SWM over Kerala takes place on 1st June and advances gradually into

other parts of India. It covers 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&PDC), Coastal Karnataka (CK),North Interior Karnataka (NIK), South Interior Karnataka

(SIK), Kerala (KER) and Lakshadweep (LAK) by 10th

June. During 2016, onset of SWM over

Kerala took place on 8th

June, 7 days behind the normal date. It covered the states of Kerala and

Tamil Nadu by 9th

June, Andhra Pradesh by 18th

June and then Telangana and Karnataka by 19th

June. As such, it took eleven 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 8th

June and its further advance into the SP region by 19th

June 2016.

Fig.1 Advance of southwest monsoon 2016 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 01st, 8

th, 18

th and 19

th June 2016 at 0300 UTC

depicting the onset of SWM 2016 over Kerala and its further advance in to the SP region

4

2. Rainfall distribution

2.1 Spatialrainfall distribution

The SWM seasonal rainfall (June-September) during 2016 over the country as a whole

was 97% of its long period average (LPA) and that over the SP region was 92% of

LPA.Cumulative seasonal (01st June to 30

th Sep) rainfall figures over the nine meteorological

subdivisions of the SP region are furnished in Table-1and district-wisespatialrainfalldistribution

over the entire SP region is presented in Fig.2.As per IMD’s classification of rainfall distribution,

if the amount of rainfall received over a region [expressed as percentage departure from normal

(PDN)] is between -19% and +19%, it is termedasnormal. If PDN is between -20% and -59%,

the region comes under deficient category, if PDN is less than -60%, the region falls under

scanty category and PDN of ≥20% indicates excess rainfall category. Subdivisions CAP, TEL,

RYS, NIK and TN&PDC received normal rainfalland subdivisions SIK, CK, KER and LAK

ended up deficient at the end of the season. Subdivisions of CK and KER which normally

receive substantial amount of rainfall (3083.8 mm and 2039.6 mm respectively) during the

season ended up deficient.

Table-1: Sub-divisional rainfall distribution over the SP region during the SWM season,

2016 (01st June-30 Sep 2016)

: Normal : Deficient

SUB-DIVISION

Actual

rainfall

(mm)

Normal

rainfall

(mm)

Percentage

departure from

normal (%)

COASTAL ANDHRA PRADESH 662.9 581.1 14

TELANGANA 899.8 755.2 19

RAYALASEEMA 392.2 398.3 -2

TAMIL NADU & PUDUCHERRY 258.1 317.2 -19

COASTAL KARNATAKA 2428.8 3083.8 -21

NORTH INTERIOR KARNATAKA 525.7 506.0 4

SOUTH INTERIOR KARNATAKA 524.5 660.0 -21

KERALA 1352.2 2039.6 -34

LAKSHADWEEP 745.5 998.5 -25

5

Fig.2 District-wise rainfall distribution (expressed as percentage departure from normal)

over the SP region during the southwest monsoon season, 2016 (01st June – 30

th Sep 2016).

District-wise seasonal rainfall distribution during the season (Fig.2) indicates the

following: (i) Barring a few districts, the entire western coastal belt of the region (all districts in

6

Kerala and many districts in CK) and most of the western districts of TN came under the

deficient category. Districts in the northern parts of the region received normal to excess

rainfall, with most districts in TEL and a few in NIK and CAP recording excess rainfall.

2.2 Month-wise rainfall performance

Monthly rainfall over the country as a whole was 89% of LPA in June, 107% of LPA in

July, 91% of LPA in August and 97% of LPA in September. In the SP region, monthly rainfall

over the 9 subdivisions is presented in Table-2. As seen, June was the only month during the

season when all the 9 subdivisions received normal to excess rainfall. July rainfall over CAP, CK

& KER was deficient and it was normal to excess in the other 6 subdivisions. August was the

driest month in the season with all the 9 subdivisions recording deficient to scanty rainfall. In

September, rainfall over the northern parts of the region was good with CAP, TEL and NIK

receiving normal to excess rainfall with TEL recording 107% excess rainfall during the month.

All other subdivisions ended up deficient to scanty. Thus the months of June and July

contributed most significantly to the seasonal rainfall over most parts of the region excepting

CAP and TEL where June and September rainfall contributed most.

Table-2: Monthly rainfall figures over the 9 subdivisions in the SP region

SUB-DIVISION

Rainfall expressed as

percentage departure from

normal (%)

June July Aug Sep COASTAL ANDHRA PRADESH 77 -21 -22 39 TELANGANA 47 -2 -40 107 RAYALASEEMA 90 39 -59 -32 TAMIL NADU & PUDUCHERRY 44 27 -36 -58 COASTAL KARNATAKA 11 -33 -38 -23 NORTH INTERIOR KARNATAKA 31 22 -39 7 SOUTH INTERIOR KARNATAKA 22 -6 -45 -54 KERALA -8 -39 -45 -66 LAKSHADWEEP -3 -9 -60 -54

7

2.3 Week by Week performance

Week by week performance of SWM 2016 over the SP region is presented in Table-3.

23rd

-29th

June was the most beneficial week for the region followed by the week prior to that,

i.e., 16th

-22nd

June. The period 4th

-24th

August saw only deficient to scanty rainfall over most

parts of the region. During 8th

-28th

September, CAP and TEL received excess rainfall and NIK

received normal to excess rainfall.

Table-3: Week by week performance of SWM 2016 over the SP region

2.4 Daily 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 87% of the days during the season over CK, on 57% of the days over KER and 46%

of the days over LAK. Fairly widespread rainfall has been realized on 40% of the days over SIK.

Isolated rainfall activity has occurred on majority of the days over the other subdivisions of the

region (CAP:37%, TEL:34%, RYS:52% &TN&PDC:78%). Fig.3a presents daily cumulative

rainfall over the entire SP region during the SWM season, 2016 (01st June-30

th Sep).

8

Table-4a: Daily spatial rainfall distribution over the SP region during SWM 2016

Month

DATE

(ENDING

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

June 08 FWD SCT FWD SCT WD FWD FWD WD FWD

June 09 SCT SCT FWD SCT WD SCT WD WD WD

June 10 ISOL ISOL ISOL ISOL WD FWD FWD WD WD

June 11 ISOL ISOL ISOL ISOL WD SCT WD WD WD

June 12 ISOL ISOL ISOL ISOL WD SCT FWD WD SCT

June 13 ISOL ISOL ISOL ISOL WD SCT SCT WD FWD

June 14 ISOL ISOL ISOL ISOL WD SCT SCT WD SCT

June 15 ISOL ISOL ISOL ISOL WD SCT ISOL WD DRY

June 16 DRY DRY DRY ISOL WD ISOL SCT WD WD

June 17 SCT DRY ISOL ISOL FWD ISOL SCT WD FWD

June 18 SCT SCT ISOL ISOL WD ISOL SCT WD FWD

June 19 SCT FWD FWD ISOL WD WD FWD WD FWD

June 20 FWD SCT FWD ISOL WD FWD SCT WD WD

June 21 SCT ISOL ISOL ISOL WD SCT FWD WD WD

June 22 ISOL SCT WD SCT WD WD FWD WD WD

June 23 ISOL ISOL ISOL SCT WD SCT WD WD WD

June 24 SCT SCT DRY SCT WD SCT WD WD WD

June 25 SCT SCT ISOL ISOL WD SCT FWD WD WD

June 26 FWD FWD ISOL ISOL WD SCT WD WD FWD

June 27 FWD SCT FWD ISOL WD FWD FWD WD FWD

June 28 FWD WD FWD ISOL WD SCT FWD WD WD

June 29 FWD ISOL FWD SCT WD FWD WD WD FWD

June 30 FWD WD ISOL ISOL WD WD WD WD FWD

July 01 FWD FWD ISOL ISOL WD FWD FWD WD FWD

July 02 SCT ISOL ISOL ISOL WD FWD FWD SCT DRY

July 03 ISOL SCT ISOL ISOL WD FWD FWD WD WD

July 04 ISOL ISOL ISOL ISOL WD SCT SCT WD WD

July 05 ISOL ISOL ISOL ISOL WD FWD WD WD WD

July 06 ISOL FWD DRY ISOL WD SCT FWD WD WD

July 07 ISOL FWD SCT ISOL WD FWD WD WD FWD

July 08 ISOL ISOL ISOL ISOL WD SCT FWD WD WD

July 09 FWD SCT ISOL ISOL FWD FWD FWD WD WD

July 10 SCT FWD ISOL ISOL WD FWD FWD WD WD

July 11 ISOL FWD DRY ISOL WD FWD FWD WD WD

July 12 ISOL FWD DRY ISOL WD WD FWD WD FWD

July 13 ISOL SCT DRY ISOL WD FWD FWD WD FWD

July 14 ISOL ISOL DRY ISOL WD ISOL SCT WD FWD

July 15 ISOL ISOL ISOL ISOL WD ISOL SCT WD WD

July 16 SCT SCT ISOL SCT WD ISOL FWD WD WD

July 17 ISOL ISOL ISOL SCT WD ISOL SCT WD WD

July 18 SCT ISOL SCT SCT WD SCT FWD WD WD

July 19 FWD SCT SCT SCT WD SCT SCT FWD FWD

July 20 SCT FWD ISOL ISOL WD WD SCT ISOL DRY

July 21 SCT SCT FWD ISOL WD WD WD FWD DRY

July 22 ISOL FWD ISOL ISOL WD FWD FWD FWD DRY

July 23 SCT FWD ISOL ISOL WD WD FWD WD WD

July 24 FWD ISOL SCT ISOL WD FWD FWD WD WD

July 25 SCT FWD SCT ISOL WD WD FWD WD WD

July 26 SCT FWD FWD FWD FWD SCT FWD SCT WD

July 27 FWD FWD FWD SCT FWD FWD FWD FWD WD

July 28 SCT FWD WD FWD WD WD WD FWD WD

July 29 SCT SCT FWD FWD WD WD WD WD SCT

July 30 SCT FWD SCT ISOL WD SCT SCT FWD DRY

July 31 FWD FWD FWD ISOL WD FWD FWD FWD FWD

9

Month

DATE

(ENDING

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

Aug 01 FWD FWD ISOL ISOL WD SCT ISOL FWD SCT

Aug 02 WD SCT SCT ISOL WD FWD SCT FWD SCT

Aug 03 FWD WD DRY ISOL WD FWD SCT SCT FWD

Aug 04 FWD WD DRY ISOL WD FWD SCT WD FWD

Aug 05 FWD SCT ISOL ISOL WD FWD FWD WD WD

Aug 06 SCT SCT ISOL ISOL WD FWD SCT WD SCT

Aug 07 ISOL SCT ISOL ISOL WD FWD FWD WD DRY

Aug 08 ISOL ISOL ISOL ISOL WD SCT SCT WD SCT

Aug 09 ISOL ISOL ISOL ISOL WD SCT SCT WD FWD

Aug 10 ISOL ISOL ISOL ISOL WD SCT SCT WD FWD

Aug 11 ISOL ISOL ISOL ISOL WD ISOL SCT FWD SCT

Aug 12 ISOL ISOL ISOL ISOL WD SCT SCT FWD SCT

Aug 13 ISOL SCT ISOL ISOL WD FWD FWD FWD FWD

Aug 14 ISOL SCT ISOL SCT WD FWD FWD FWD SCT

Aug 15 ISOL ISOL ISOL ISOL WD SCT SCT WD WD

Aug 16 SCT ISOL ISOL ISOL WD SCT FWD WD FWD

Aug 17 ISOL ISOL DRY ISOL WD SCT FWD WD WD

Aug 18 DRY ISOL DRY ISOL WD ISOL SCT WD WD

Aug 19 DRY ISOL ISOL ISOL WD ISOL SCT WD FWD

Aug 20 ISOL ISOL DRY ISOL WD ISOL SCT FWD WD

Aug 21 ISOL ISOL ISOL ISOL FWD ISOL ISOL SCT WD

Aug 22 ISOL ISOL ISOL ISOL WD SCT SCT ISOL FWD

Aug 23 ISOL ISOL ISOL ISOL WD SCT SCT SCT DRY

Aug 24 ISOL SCT DRY ISOL WD FWD FWD FWD FWD

Aug 25 SCT SCT ISOL ISOL WD SCT SCT WD WD

Aug 26 FWD SCT ISOL ISOL WD SCT SCT FWD WD

Aug 27 WD SCT ISOL SCT WD ISOL FWD FWD FWD

Aug 28 WD FWD ISOL ISOL WD SCT FWD WD SCT

Aug 29 FWD SCT ISOL SCT WD SCT SCT FWD FWD

Aug 30 FWD FWD FWD SCT WD SCT FWD FWD FWD

Aug 31 FWD WD FWD FWD WD WD WD WD WD

Sep 01 FWD FWD SCT SCT WD SCT WD WD WD

Sep 02 SCT FWD ISOL SCT WD SCT SCT FWD WD

Sep 03 FWD FWD ISOL SCT WD SCT SCT WD WD

Sep 04 SCT ISOL ISOL ISOL WD ISOL FWD FWD WD

Sep 05 FWD FWD ISOL ISOL FWD DRY FWD ISOL FWD

Sep 06 DRY DRY DRY DRY WD DRY ISOL ISOL WD

Sep 07 ISOL ISOL ISOL ISOL WD ISOL FWD ISOL DRY

Sep 08 ISOL DRY DRY ISOL WD ISOL ISOL ISOL FWD

Sep 09 ISOL ISOL DRY ISOL SCT ISOL ISOL ISOL WD

Sep 10 SCT SCT ISOL ISOL ISOL ISOL ISOL ISOL DRY

Sep 11 SCT FWD SCT ISOL SCT SCT SCT ISOL SCT

Sep 12 SCT FWD SCT ISOL FWD SCT SCT ISOL WD

Sep 13 FWD WD SCT ISOL FWD SCT SCT SCT WD

Sep 14 FWD WD SCT ISOL WD WD SCT SCT FWD

Sep 15 WD WD SCT ISOL WD WD WD WD WD

Sep 16 FWD WD SCT ISOL WD WD FWD FWD WD

Sep 17 ISOL SCT SCT ISOL WD FWD SCT FWD FWD

Sep 18 SCT SCT ISOL ISOL WD SCT SCT ISOL WD

Sep 19 ISOL ISOL ISOL ISOL WD SCT SCT FWD SCT

Sep 20 ISOL ISOL SCT ISOL WD SCT ISOL ISOL SCT

Sep 21 WD WD WD ISOL WD FWD FWD WD FWD

Sep 22 WD WD FWD ISOL WD WD WD WD FWD

Sep 23 FWD WD ISOL ISOL WD FWD SCT SCT WD

Sep 24 WD WD SCT ISOL WD FWD FWD WD SCT

Sep 25 FWD WD SCT ISOL WD WD FWD FWD SCT

Sep 26 FWD WD SCT ISOL WD FWD FWD FWD WD

Sep 27 FWD FWD SCT ISOL FWD SCT SCT FWD SCT

Sep 28 SCT FWD ISOL ISOL SCT ISOL ISOL ISOL WD

Sep 29 SCT ISOL SCT SCT SCT SCT SCT FWD WD

Sep 30 FWD ISOL ISOL SCT ISOL SCT SCT SCT SCT

10

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

over the subdivisions of the SP region during SWM 2016

Category

Frequency (%)

CAP TEL RYS TN&PDC CK NIK SIK KER LAK

WD 6 13 3 87 14 14 57 46

FWD 28 24 13 4 8 28 40 24 30

SCT 26 25 18 17 3 40 38 8 16

ISOL 37 34 52 78 2 17 8 11

DRY 3 3 14 1 2 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.3a Daily cumulative rainfall over southern peninsular region during SWM season,

2016

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

the various subdivisions of the SP region during SWM 2016. Telangana experienced maximum

days of active to vigorous monsoon conditions (36 days) followed by CAP (29 days) and RYS

11

(19 days) during the season. Least number of days of active to vigorous monsoon activity has

been over KER and TN&PDC (4 days each) followed by CK (10 days).

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

SP region during SWM 2016

Subdivision No. of days

VIG ACT COASTAL ANDHRA PRADESH

6 23 TELANGANA

10 26 RAYALASEEMA

9 10 TAMIL NADU & PUDUCHERRY

3 1 COASTAL KARNATAKA

1 11 NORTH INTERIOR KARNATAKA

4 14 SOUTH INTERIOR KARNATAKA

1 15 KERALA

-- 4 LAKSHADWEEP

-- -- 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)

2.5 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 2016. Maximum number of heavy rainfall

days have been recorded in Telangana (58) followed by SIK (57), CAP (55) and CK (54).

Extremely heavy rainfall (≥ 21cm/day) have been recorded on 4 days in Telangana, on 3 days in

SIK, 2 days in CAP and one day each in CK, RYS and Kerala (Table-6b).

Highest rainfall of 39 cm has been recorded in Nizamabad district of Telangana on 24th

Sep2016 at Armur, followed by 32 cm at Machareddy on 25th

Sep.

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

TEL/ CAP as on 0830 IST of 31st Aug and 23

rd-25

th Sep 2016 as depicted by IMD-NCMRWF

GPM satellite-Gauge merged rainfall is presented in Fig.3b.

12

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

June-Sep 2016

Subdivision

No. of days of Heavy rainfall

(Rainfall ≥ 7 cm in 24 hrs)

Extremely

Heavy

(≥21 cm)

Very

Heavy

(12-20 cm)

Heavy

(7-11cm) COASTAL ANDHRA PRADESH

2 10 43 TELANGANA

4 15 39 RAYALASEEMA

1 1 23 TAMIL NADU & PUDUCHERRY

-- 4 29 COASTAL KARNATAKA

1 13 40 NORTH INTERIOR KARNATAKA

-- 1 8 SOUTH INTERIOR KARNATAKA

3 15 39 KERALA

1 5 37 LAKSHADWEEP

-- -- -- Note: Kindly refer Appendix-(ii) for explanations on various terminologies used for description of rainfall

intensity.

Table-6b Details of Extremely Heavy rainfall occurrences during Jun-Sep 2016

Subdivision Date Rainfall amount and Station COASTAL ANDHRA

PRADESH 28-Jun-2016 23 cm - Vellairpad (West Godavari)

13-Sep-2016 23 cm – Jangameshwarapuram ARG (Guntur) TELANGANA 01-Aug-2016 22 cm – Metpalle (Karimnagar)

31-Aug-2016 22 cm – Peddemul (Ranga Reddy) &

21 cm-Pargi (Renga Reddy)

24-Sep-2016 39 cm – Armur (Nizamabad)

25-Sep-2016 32 cm – Machareddy (Nizamabad) &

27 cm – Kamareddy (Nizamabad) RAYALASEEMA 30-Aug-2016 23 cm – Duvvur (Cudappa) COASTAL

KARNATAKA 29-Jun-2016 25 cm – Kollur (Udupi) &

Gersoppa (Uttara Kannada) SOUTH INTERIOR

KARNATAKA 29-Jun-2016 26 cm - Hulikal ARG (Shivamogga)

&Bhagamandala (Kodagu);

22cm – Agumbe (Shivamogga)

5-Jul-2016 21 cm – Agumbe (Shivamogga)

21-Jul-2016 29 cm – Chittapur (Kalaburgi) KERALA 29-Jun-2016 27cm-Mananthavady (Wayanad)

13

Fig.3b GPMsatellite-Gauge merged rainfall in cm depicting isolated very heavy (12-20

cm/day) to extremely heavy(≥ 21cm/day) rainfall over TEL on 31st Aug and 23rd-25

th Sep

2016

14

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 2016 are depicted in Fig.4. The

SPI indicates extremely/ severely/moderately dry conditions over most districts of Kerala and

Lakshadweep, many districts of Coastal Karnataka, few districts of South Interior Karnataka

and one or two districts of Tamil Nadu during the SWM season of 2016.

Fig.4 Standardised Precipitation Index (SPI) over the SP region during Jun-Sep 2016

2.7 Chief synoptic features

Fig.5 depicts the 850, 500 and 250 hPa wind anomaly during the months of June, July

August and September 2016. As seen, anomalous easterly flow over the southern parts of

Arabian Sea and the SP region in the lower to mid-troposphere caused weaker monsoon activity

in June. A low pressure area that formed over westcentral& adjoining northwest Bay of Bengal

off north Andhra Pradesh-south Odisha coasts moved inland and caused active to vigorous

monsoon conditions over CAP and TEL during the last of week of June.

In July, stronger westerly anomalies are noted over the northeast Arabian Sea in the

lower to mid-troposphere which helped in the revival of the monsoon in July. Two low pressure

areas that formed over north Bay of Bengal towards the end of July to early August moved

15

nearly west-northwestwards along the monsoon trough and caused active to vigorous monsoon

conditions over northern parts of peninsular India with extremely heavy rainfall activity at

isolated places.

In August, strong anti-cyclonic circulation anomaly was observed in the lower

troposphere over the southern parts of Arabian Sea, SP region and southwest Bay of Bengal

which caused subsidence over the SP region resulting in deficient monsoon over the entire region

during this month.However, a cyclonic circulation over westcentral Bay of Bengal off Andhra

Pradesh coast caused FWD to WD rainfall activity with isolated extremely heavy falls over the

eastern parts of the SP region towards the end of August.

During September, due to formation of three low pressure areas over the Bay of Bengal

active to vigorous monsoon activity prevailed over many parts of the region. In the third week,

favourable MJO conditions strengthened the monsoon circulation and increased convective

activity leading to active to vigorous monsoon activity over the northern parts of the SP region.

16

Fig.5: 850hPa, 500 hPa& 250 hPa wind anomalies over Indian region during SWM 2016

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

17

Fig.5 contd. …

18

3. Withdrawal of SWM 2016 from the SP region

Withdrawal of SWM 2016 from the SP region commenced on 15th

October over northern

parts of Telanganaandgradually proceeded southwards. With the gradual setting in of

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

28th

October 2016. Fig.6 depicts gradual withdrawal of SWM 2016 from various parts of the SP

region.

4. Summary

Fig.6 Isolines of dates of withdrawal of SWM 2016 over the SP region

4. Summary

During 2016, onset of southwest monsoon over Kerala took place on 8th

June, late by

about a week. It gradually advanced into the other subdivisions and covered the entire southern

peninsular region by 19th

June against the normal date of 10th

June. Despite the late arrival of

SWM, rainfall was excess to normal over the 9 met subdivisions of the SP region in the month of

June. July rainfall became deficient over KER, CK and CAP, but, all the other 6 subdivisions

received normal to excess rainfall. However, monsoon performance in the month of August over

the entire SP region was poor with all the nine subdivisions of the region recording deficient to

scanty rainfall. Passage of three low pressure systems over the northern parts of the SP region in

the month of September caused good monsoon activity over the northern parts with TEL and

CAP recording excess and NIK receiving normal rainfall during September. At the end of the

season, most of the southern region of the SP region ended up deficient while northern region

recorded excess rainfall.

19

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.

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