(Map by Tejas Baxi.)
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MONSOON REPORT (01-9-2016 TO 30-9-2016)
TOTAL ALL INDIA RAINFALL (as on 30-9-2016)	862.0 mm
SEASON +/-	-2.87%
RAINFALL PER DAY this season	7.07 mm
SEPTEMBER RAINFALL (2016)	168.9 mm
AVERAGE SEPTEMBER RAINFALL (1966 TO 2015)                                                              #	168.1 mm
SURPLUS	+0.5%
TOP FIVE SUBDIVISIONS THIS MONTH	mm
A & N ISLAND	604.3
KONKAN & GOA	600.2
ARUNACHAL PRADESH	530.1
SHWB & SIKKIM	514.4
BIHAR	357.9
BOTTOM FIVE SUBDIVISIONS THIS MONTH	mm
JAMMU & KASHMIR	44.5
EAST RAJASTHAN	40.2
PUNJAB	16.9
HAR. CHD & DELHI	15.5
WEST RAJASTHAN	11
TOP FIVE SUBDIVISIONS ABOVE NORMAL THIS MONSOON
EAST RAJASTHAN	32%
KONKAN & GOA	22%
MARATHWADA	21%
WEST RAJASTHAN	20%
TELANGANA	19%
BOTTOM FIVE SUBDIVISIONS BELOW NORMAL THIS MONSOON
LAKSHADWEEP	-25%
HAR. CHD & DELHI	-27%
PUNJAB	-28%
ASSAM & MEGHALAYA	-30%
KERALA	-34%
TOP FIVE STATES THIS MONTH	mm
SIKKIM	632.6
ANDAMAN & NICOBAR (UT)	604.3
ARUNACHAL PRADESH	530.1
MIZORAM	417.2
MANIPUR	405.3
BOTTOM FIVE STATES THIS MONTH	mm
JAMMU & KASHMIR	44.5
CHANDIGARH (UT)	41.5
RAJASTHAN	24
PUNJAB	16.9
HARYANA	13.6
TOP FIVE STATES ABOVE NORMAL THIS MONSOON
RAJASTHAN	28%
DADAR & NAGAR HAVELI (UT)	26%
TELANGANA	19%
MADHYA PRADESH	19%
MAHARASHTRA	16%
BOTTOM FIVE STATES BELOW NORMAL THIS MONSOON
PUNJAB	-28%
HARYANA	-28%
KERALA	-34%
CHANDIGARH (UT)	-46%
MEGHALAYA	-48%
TOP TEN DISTRICTS THIS MONTH	mm
UPPER SIANG (arunachal pradesh)	1169
WEST SIKKIM (sikkim)	1021.1
EAST SIANG (arunachal pradesh)	925.5
LOWER DIBANG VALLEY (arunachal pradesh)	793.4
RATNAGIRI (maharashtra)	793.1
RAIGARH (maharashtra)	788
SOUTH ANDAMAN (a & n Island)	770.9
IMPHAL WEST (manipur)	737.6
MUMBAI CITY (maharashtra)	733.4
PAPUM-PARE (arunachal pradesh)	714.6
BOTTOM TEN DISTRICTS THIS MONTH	mm
BADGAM (j & k)	2.2
TUTICORIN (tamil nadu)	1.9
BHIWANI (harayana)	1.3
JAISELMER (rajasthan)	1.2
SANGRUR (punjab)	0.9
BATHINDA (punjab)	0.9
ROHTAK (harayana)	0.7
TIRUNELVELI (tamil nadu)	0.4
HISAR (harayana)	0.2
LEH AND LADAKH (j & k)	0.1
(TARAN TARAN, SIRSA, MUKTSAR, MORBI, MOGA, MANSA, KAITHAL, JIND, FATEHABAD, FARIDKOT, BARNALA all had 0 mm rainfall)	0.0
TOTAL ABOVE AVERAGE RAINFALL DAYS this month (subdivision data)	13  (43%)
TOTAL BELOW AVERAGE RAINFALL DAYS this month (subdivision data)	17 (57%)
# IMD figures are different as this is 50 year average	source -IMD

 

Estimate for Next 2 days Wednesday 28th and Thursday 29th September for :-

Delhi NCR: As monsoon withdraws by month end, Region may experience very hot days. Day may rise to 38c.

Mumbai: Partly cloudy with a couple of passing showers in some parts of city. Days likely to be hotter.

Kolkata: Warm, but a shower or thunder shower expected on Wed/Thursday.

Chennai: Cloudy, with showers on Wednesday and Thursday. Around 10-20 mms of average rainfall per day.

Bangalore: Expecting a thundershower on Wednesday and Thursday.

Hyderabad: Partly cloudy. May get windy on Thursday. Light drizzle in some parts.

Posted Monday Night:
Mumbai will get periods of sunshine with a few passing showers on Tuesday, maybe upto 10 mms in the day/night. Rest of the week will be seeing periods of sunshine with a few showers in some parts. Decreased rain continues till month end. 

Mumbai's Evening thunder showers (from East) may start by next month.

Mumbai Rainfall Stats:( 25th September)

Seasonal Totals:
Colaba: Mumbai Colaba crosses 2500 mms for this season...2507 mms As on 26th September.
Recent crossing 2500 mms was in 2011 when Colaba measured 2879 mms ( Full Season) and in 2010 when this station saw 3291 mms till Monsoon withdrawal.
Highest ever Seasonal total for Colaba is 3482 mms in 1954.
Santacruz:  Total on 26th September for this season stands at 2893 mms.
Recently in 2010, SCruz measured 3392 mms till Monsoon withdrawal. Highest ever at Scruz is 3785 mms in 1958.

September Totals;
Colaba: This year 2016, as on 25th September, this Month has recorded 731 mms , while wettest ever September was in 1988 and 1993, when 832 mms was recorded.
Santa Cruz:2016 September, Scruz has received 703 mms, still short of the record september of 1993 when the month saw 905 mms.

Incidentally,  2011 had the Longest Monsoon Season for Mumbai, when the Monsoon withdrew on 24th October, after lasting 141 days !

Posted Saturday Night:

BB-13 persists over Telengana/Vidharbh. Expected to remain in region next 2 days. Heavy rains continue in parts of Telengana and Vidharbh. Hyderabad next 2 days : Some heavy showers.

Mumbai sees a sharp reduction in rains....Sunday thru Tuesday will be partly cloudy with sunny periods. 4/5 passing showers in parts of city. Major decrease in rains from Monday.

Sunday thru Tuesday:Light rains (upto 5 mms) occurring along South Gujarat coast (Valsad and Surat).

Jaipur had a heavy "end of season" shower of 59 mms Friday night and Churu received 38 mms on Friday night.
As mentioned, South West Monsoon all set to withdraw from Saurashtra, North Gujarat and East Rajasthan by Monday 26th September.
Days will be over 40c in Rajasthan and Kutch.

Yesterday in the comments section I gave a brief analysis of "Peninsular" rainfall for the period 1871 to 2014 during the monsoon months, June to September.

Today we look at the same set of data ((via IITM under the All India and Macro Regional data set. (It includes six subdivisions namely Coastal Andhra Pradesh, Rayalseema, TN & Pondicherry, Coastal AP ,S I Karnataka and Kerala)) of the "Peninsular" rainfall for the period October to December.

This period is normally classified as the NEM and this is what IMD Chennai says about it..

"The period October to December is referred to as Northeast Monsoon season over peninsular India. Earlier   this period was also referred to as 'Post-Monsoon Season' or 'Retreating southwest Monsoon Season'.

Northeast Monsoon season is the major period of rainfall activity over south peninsula, particularly in the eastern half comprising of the meteorological subdivisions of Coastal Andhra Pradesh, Rayalaseema and Tamilnadu-Pondicherry. For Tamilnadu this is the main rainy season accounting for about 48% of the annual rainfall. Coastal districts of the State get nearly 60% of the annual rainfall and the interior districts get about 40-50%  of the annual rainfall. 

Though the principal rainy season for  Interior Karnataka, Kerala and Lakshadweep is the Southwest Monsoon season, rainfall continues till December in these sub-divisions, the period October-December (Northeast Monsoon ) contributing about 20 % of the annual total. " 

First we look at a graphical representation of the raw data from 1871 to 2014..

As can be seen the rainfall varies from as low as 93mm in 1876 to 585mm in 1946. Those are the extremes. The average for the entire 144 years is 345mm.

Now we look at a smoother version of the above data which has been averaged every three years..

 As can be seen there is a cyclical behavior that seems to swing between highs and lows every few decades. The lows are formed every 35 to 45 years and since the last one was in 1990 the next can be expected around 2025 to 2035 (since it is averaged for the previous three years the actual lows might form from 2022-25 or 2032-35).

An even more smoother version (9 years) gives us this ;

 Here too we get the same 35 to 45 year lows in rainfall.

We now compare the Peninsular Oct to Dec rainfall to the Annual Peninsular rainfall for all the years;

(smoothed every nine years)

Same conclusions as above!!! Also the range varies from 35% (1888) to 25%(1955).

And finally we compare the Peninsular Oct to Dec rainfall with the Peninsular Monsoonal rainfall;

(smoothed every nine years)

Again the same conclusions as far as the lows are concerned. The range varies in this case from 65%(1888) to below 45%(1912,1955).

Conclusions: The Peninsular rainfall from Oct to Dec shows a huge variation from 93mm to 600mm and ranges between 25% to 35% of its annual rainfall averaging around 29.5%. As compared to the south west Monsoon it varies from below 45% to almost 65% averaging around 54%. A cyclical behavior is very evident in the charts above and the current century shows nothing unusual.

The fact that some kind of regularity has been seen in the trend for the last 144 years does not suggest at all that a new trend might not emerge in the future..weather is too complicated for any one to truly predict accurately a hundred per cent all the time. I personally feel a time period of 150 years is too short for any kind of definitive trends to be emerge.

 

((Thanks to IITM for the data and IMD Chennai for the NEM introduction)) 

Posted Tuesday Night:

Mumbai received intermittent showers on Tuesday Night and Wednesday. From 8.30 am - 8.30 pm IST on Wednesday, Colaba measured 99 mms and Scruz 57 mms. 

On Thursday, Mumbai city will get marginally less rains as experienced on Wednesday. Less frequency passing showers, not continuous,  will measure around 40-60 mms from Thursday Morning - Friday morning. (Less Compared with Wednesday figures). 

Northern Outer townships have received the brunt of the heavy rains recently. They will get much reduced rainfall next 2 days.

Friday: Frequent showers, some heavy. Though not intermittent or continuous, the rainfall will be almost the same as Thursday amounts.

Pune: Few light showers on Thursday, rain frequency increasing to 15-20 mms on Friday. Cool days.

All Lakes supplying water to Mumbai on the brim now, 99% full. Mumbai has water storage for 385 days, i.e. till 11th October 2017 !!..Lakes Info from Vagarian Jayesh Mehta.

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A low from the Bay will cross the AP coast on Thursday/Friday. An extended upper air trough from the system will cross the South Konkan coast , forming by Saturday. Increasing rains in South Konkan and Goa from Saturday. More on this later.

South West Monsoon may withdraw from Saurashtra by 24th September.

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Mumbai: From Tuesday mid night till  Wednesday mid night, Colaba received 113 mms and Scruz 75 mms.Vagaries measured 89 mms.

Estimate given for 24 hrs ended midnight Wednesday was "More rains for Mumbai Tuesday Night...70-90 mms from Midnight Tuesday next 24 hrs...Posted Tuesday Night"

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