Wednesday, September 19, 2012

Hitting the Bullseye - SW Monsoon Rainfall: 94% of LPA: Our forecast 94%!





July 3rd 2012: Revised Forecast

Monsoon Forecast: Give the Met Dept a break. They are still on target and so are we!

http://devconsultancygroup.blogspot.in/2012/07/monsoon-forecast-give-met-dept-break.html

Forecast 94.5 of LPA (91-98% LPA) Confidence Level 95%


Our revised rainfall forecast of 94.5% of Long Period Average (LPA) or 91-98% of LPA range was made at a time when rainfall deficiency in the country was over 32% and the Indian Meteorological Department  (IMD) was being castigated for their revised forecast of 96% of LPA. Apart from being published in our blog, it was re-published in the financial magazine, Moneylife. Read here At the time we made the forecast, because of media going overboard with their drought hysteria, not many took our forecast seriously.

While we kept this revised forecast unchanged thereafter, the IMD presumably caving to pressure of a very bad press and politicians, revised their forecast downwards to first 90% of LPA by beginning of August and within a week, revised it even lower to 85% of LPA. Nearly all major global models forecasted even earlier a deficient monsoon viz below 90% to 80% range.

With rainfall at 94% as of date and expected to end the season within the 96-98% of LPA range, this makes ours among those published their forecasts, the only one who hit the bulls eye.

April 10th, 2012: Early Forecast

Normal Monsoon Forecast: Indian Ocean Dipole (IOD), the Wild Card

http://devconsultancygroup.blogspot.in/2012/04/normal-monsoon-forecast-indian-ocean.html

Forecast 100% of LPA (96-104% LPA) Confidence Level 70%

There were practically no difference in outlook between our April early forecast and our revised July forecast in terms of how we saw critical climatic events influencing the monsoon expected to pan out except in relation to the assumption how an El Niño would pan out.

In early April when we made our early forecast, it was not certain whether an El Niño event will occur this year. By July, El Niño threshold values were observed in the Central Equatorial Pacific Ocean. We however treated the El Niño would have no impact on the Indian Monsoon and if at all it does, September, the last month of monsoon would be hit somewhat.

This El Niño outlook we shared with only those of the IMD but differed with most global models that forecasted drought in the country because of the El Niño impact. Our confidence in ruling out the El Niño impact was on account of two major assumptions that was validated:

a.   The Central Equatorial Pacific Ocean had experienced a back-to-back La Niña during 2010-2011 and 2011-12. Logically two years of cooling should result in the Central Equatorial Pacific Ocean accumulating little heat during this period and at the most we should have a very weak El Niño if any


 b.   Even if there is a strong El Nino, as seen in the above graph, there is a lot of cold water circulating from Alaska down the west coast of Canada, the US and Mexico. This cold water is mixing with equatorial Pacific waters and keeping SSTs in equatorial Pacific down.  That ruled out a strong El Niño event emerging this season.


Though there are several factors that condition the Indian Monsoon, our hypothesis was that in each monsoon, one climatic factor emerges as the main driver of the monsoon for each season. This could be the El Niño in one season, the La Niña in other season or the Indian Ocean Dipole (IOD) etc.

In our April early forecast, we identified the IOD as the wild card. Even in our revised first week July forecast, when most models were assuming the El Niño as the wild card, we continued to consider the IOD as this season’s wild card. The Japan Meteorological Agency (JMA) forecasted a negative IOD which was detrimental to rainfall while the IMD forecasted a neutral IOD. We had in contrast forecasted a positive IOD which in addition to be favourable for rainfall can also swamp the effects of an El Niño.

This El Niño outlook we shared with only those of the IMD but differed with most global models that forecasted drought in the country because of the El Niño impact. Our confidence in ruling out the El Niño impact was on account of two major assumptions that was valid

Though there are several factors that condition the Indian Monsoon, our hypothesis was that in each monsoon, one climatic factor emerges as the main driver of the monsoon for each season. This could be the El Niño in one season, the La Niña in other season or the Indian Ocean Dipole (IOD) etc.

In our April early forecast, we identified the IOD as the wild card. Even in our revised first week July forecast, when most models were assuming the El Niño as the wild card, we continued to consider the IOD as this season’s wild card. The Japan Meteorological Agency (JMA) forecasted a negative IOD which was detrimental to rainfall while the IMD forecasted a neutral IOD. We had in contrast forecasted a positive IOD which in addition to be favourable for rainfall can also swamp the effects of an El Niño.

For the whole of June-July, the IOD demonstrated neutral values with a negative bias which saw rainfall being affected in the country. But by beginning of August, it switched to its strongly positive mode that saw very heavy rainfall all over the country.

We had also assumed once the main driver of the season’s monsoon falls into place, all other elements follow. Such a hypothesis is not backed up by any scientific literature but that is exactly what apparently happened this season. Once the IOD turned strongly positive, other key elements like the Madden Julian Oscillation (MJO) and the North Atlantic Oscillation (NAO) turned positive, whether coincidence or not. Their combined effect saw the western trough of the monsoon which was weak during June-July strengthen from August beginning onwards one-hand and increased and stronger western disturbance (westerlies) on the other-hand that together brought rainfall to the heavily parched north-western regions of our country.

This had been the first monsoon forecast. We undertook for basically two reasons. The first could be traced to yielding to the temptation of monsoon forecasting, considered one of the most challenging of climatic events. For years I religiously followed the forecasts of my friends within the independent community of weather, particularly Rajesh Kapadia’s blog - Vagaries of the Weather, where I picked up some of the fundamentals to weather forecasting. Rajesh is not only a good teacher but possibly one of the best weathermen in the country today. Then there are others like young Akash Deoras and his blog Metd Weather and Ashok Patil and his blog Gujarat weather.com whose blogs and inter-actions with helped be pick up the fundamentals of forecasting.

Secondly, I had been a harsh critic of NGO climate smart agriculture (CSA) programmes. The monsoon is the single most significant element of climate with respect to agriculture. And yet, none of these NGOs whether Oxfam; ActionAid; Gene Campaign etc do not even come out with their own monsoon forecasts. When NGOs are not able to even able to forecast the Indian Monsoon, their claims to CSA remain thoroughly bogus. As a member of the NGO fraternity, by publishing my monsoon forecasts I was actually throwing down a gauntlet at them to publicly prove their climate smartness claim by their publishing monsoon forecasts.

 

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