Monsoons September 2015 - Normal for the month - but - Deficient ending for the Season!

September 30, 2015 marks the official end of the South West Monsoon Season for 2015.

Though monsoon has withdrawn from most of India North of Vindhyas, it is expected to linger in Goa for a few more weeks in October.

Even then, September end is the right time to look at the performance of the SW Monsoon in Goa for 2015.

Fig 1a

Fig 1b

Fig 1c: Source - http://www.imdgoa.gov.in

During September 2015, Goa received normal rainfall. Area weighted average rainfall rainfall of 293 mm was recorded against normal of 280 mm (+5%). However due to deficient rains in June, July and August, the cummulative rainfall recorded was just 2389 mm (94 inches), against normal 2972 mm (117 inches). This resulted in deficiency of -20% for the seasonal.

As per IMD norms, for seasonal rainfall at regional level, rainfall between -20% to -59% is classified as deficient.

However though September yielded +5% rainfall, there were just 9 days out of 30 days in September with rainfall more than 3 mm, as recorded by Vagaries Goa Rain Gauge at Aquem, Margao.

Fig 2

Canacona recorded the highest rainfall during September and Dabolim the lowest.

Fig 3a

Fig 3b

September 2015 rains were also lower than September 2014 rains.

Fig 4

As expected the foothills of Western Ghats received the highest rainfall during the season. However what was unexpected was Sanguem, in South Goa with 3079 mm (121 inches), outperforming Valpoi , the usual topper, at just 2741 mm (108 inches). Surprisingly too Pernem in North Goa, which usually receives good seasonal rainfall, received poor rainfall with just 1865 mm (73 inches).

Fig 5a

And in Google Earth with seasonal rainfall in mm:

Fig 5b

The month-wise rainfall chart shows that while Sanguem received good rainfall every month, Valpoi received poor rains in September.

Fig 6

Comparing the seasonal rainfall at all the rain centers in Goa over last three years, dramatically illustrates the poor performance of the monsoons in Goa this year, as against 2013 and 2014.

Fig 7

The performance of the SW monsoons is in the deficient category on all India level too as per this map from IMD:

Fig 8

While IMD can take comfort from the fact that it had predicted the seasonal rainfall during 2015 to be +/- 88% of LPA with error of +/- 4%, in its Long Range Forecast update issued on June 2, 2015, the performance of the monsoons on the West Coast of India is one of the worst in recent times.

Meteorologists are attributing the deficient rains during SW Monsoons this year to the strong El Nino phenomenon that continues even as the SW monsoon season ends in India. We are going to hear a lot about the effect of El Nino in coming days, on the Monsoons in India this year.

The break in Monsoon in September saw significant rise in temperatures in the second half of September, as recorded at Panjim by IMD:

Fig 9a

The highest day temperature of 34.8C and highest night temperature of 26.2C were both recorded on the last day of the month i.e. September 30

Fig 9b

While comparison of SWM 2015 with other failed monsoon years like 2002, 2009, 2012 is inevitable, What stands out is the failure of the Arabian Sea branch of the monsoons in 2015, leading to deficient monsoon all along the west coast. The saving grace for SWM this year has been undoubtedly The Bay of Bengal Branch, bringing good rains to the east coast and to central India too!

The analysis of SWM 2015 will continue for a long time to come. Keep an eye on this blog for regular updates!

Day Temperatures Touching record highs for the month! - Posted September 25, 2015

With no rains past few days day and night temperatures have been scaling new highs for this time of the month.

On September 24, 33C was the maximum day temperature recorded at Panaji. This is 2C above normal.

The minimum temperature is also nearing 25C, again around 2C above normal.

With no chance of rains for next few days, the heat index would be high in Goa and necessary precautions should be taken for outdoor activities.

Warm, Sunny Days ahead for this week - Posted September 23, 2015

With the low BB6 which originated in Bay of Bengal and then crossed overland into Gujarat, now merged with the seasonal low, the system which brought lot of rains to Central and Western parts of India is dead and Goa has ceased to benefit any more from the system.

As a result from September 20th, Goa has been experiencing light to nil rains.

Warm and sunny weather is expected to remain, at least till this weekend.

Day temperatures are nearing 32C, nearly 1-2 C above normal. Minimum temperature hovers above 24C.

The seasonal deficit continues to be -18%, with average area weighted rainfall so far from June 1 at 94 inches as against the normal of 114 inches. Seasonal rainfall in the range -19% to +19%  is considered "Normal" Monsoon! So we can now say that Goa has so far received normal monsoon rains!

Valpoi is losing the "wettest Place in Goa" title to Sanguem this year. But what is also very surprising is the poor rainfall in Pernem area.

More analysis September month - end!

Rainy Ganesh Chaturthi in Goa, Rains expected to decrease from Saturday 19th - Posted September 18, 2015

South Goa was lashed by heavy rainfall on the night of September 17 - 18.

In 24 hrs till 0830 hrs on Friday September 18, Vagaries Goa had recorded 110 mm and IMD Centres at Margao (73.1 mm), Sanguem (97.7 mm), Quepem (73.8 mm) and Mormugao (62 mm).

The medium to heavy rains in the last three days helped bring down the seasonal deficit for Goa to -18%.

 Source: http://www.imdgoa.gov.in

These rains were due to the revival of monsoon trough off the west coast of India under the influence of the deep depression BB6, as it moved from Bay of Bengal westwards.

As BB6 has taken a northward course over land, and is now approaching Gujarat, rains along the the west coast will shift towards North Konkan, Mumbai and Gujarat from Friday itself.

Source: http://www.vagaries.in

However meteologists are closely monitoring the possibility of another system developing in Bay of Bengal around 23 - 25th September, which could bring rainfall to the southern peninsula, similar to BB6.

Till than expect light rains in Goa.

Low in Bay of Bengal brings rain for Ganesh Chaturthi!

As mentioned in the last post, the Low BB6, formed in the North Bay of Bengal and by September 15, was crossing the coast near Odisha/ A. P. Under its influence the Monsoon trough off the west Coast of India has revived, bringing good rains all along the coast. Thunderstorm activity is also seen at many places in the country.

Goa has been receiving moderate to heavy rains at most places since last three days. Vagaries Goa has recorded 91 mm rainfall in three days since September 12, bringing the total rainfall received in the first half of September to 109 mm, far below the normal. As can be seen in the graph below, only 5 days in the last 15 days have received rains more than 2 mm.

The Seasonal deficiency for Goa continues to be at -23% below normal. Goa has received area weighted average rainfall till September 15, of nearly 87 inches, compared to a normal of 112 inches, this time of the year.

Source: http://www.imdgoa.gov.in

The rainfall recorded at the various rain gauge centres in Goa during the first 15 days of September is as follows:

So, the rainfall of 4-5 days in September so far has been of hits and misses, with some areas receiving more than others.

Sanguem and Valpoi have crossed the century mark in inches and Ponda and Sanquelim are close behind, in the seasonal tally.

As mentioned in this post in the blog Vagaries of the Weather, the low BB6 is expected to cross and emerge as a low in the Arabian Sea around September 18/ 19, keeping the trough active, with rains in Konkan, Gujarat and Goa.

Happy Ganesh festival to you all!

Low Forming In Bay of Bengal around 11-12th September could bring rain to Goa next week - Posted September 10, 2015

After a big lull in SW Monsoon rains in 1st week of September, Goa received some activity on 8th, 9th and 10th. Though this was mainly 'hits and misses' rains, with some areas like Mapusa, Sanguem, Sanquelim receiving heavy rains on a given day, and some centres receiving NIL rains! For daily rainfall figures checkout this page.

From weighted average rainfall for Goa of 2 mm on 8th to 20 mm on 9th and 12 mm on 10th, the overcast conditions brought down the day max temperatures from 32.1C to 29.8C and minimum temperature from 25.5C to 23.3C.

But the seasonal deficiency continues to be more than 24% below normal.

Source: http://imdgoa.gov.in

However as detailed in the weather blog Vagaries of The Weather, a low is expected to form in Bay of Bengal around 11th - 12th. Named as BB6, the Low is expected to track West towards M.P. due to strong resistance in the North. This movement of the Low is expected to bring good rains to Maharashtra and Konkan including Goa next week.

The SW Monsoon has withdrawn from Pakistan, Rajasthan and parts of Punjab and Harayana. But the formation and movement of BB6 will slow the withdrawal south of M.P. for the time being. This is definately a good news to west coast and parts of South Peninsula, which have received deficient rains so far this season.