IMD's Weak 2015 Monsoon Prediction Not The Gospel Truth

The Indian Meteorological Department has expressed fears of El Nino causing a weak 2015 monsoon. But this is to be taken with a pinch of salt. The IMD's predictions in the past have often been wide off the mark.

We reproduce below what the Wall Street Journal has to say about this.

India’s weather department this week unveiled its annual early forecast of how much rain the monsoon will likely dump on the Subcontinent this year. A precise prediction is crucial for the hundreds of millions of farmers who depend on the annual rains but history shows that these early forecasts are usually wrong.

Last year the India Meteorological Department predicted a slightly weak monsoon, but India got a drought. The year before it forecast below-average rains, and the subcontinent got well above average. In 2009 when India had its worst drought in decades, the IMD had predicted a normal monsoon.

The government’s weather watchers use the average rainfall for the last 50 years to define what is normal. If the rainfall for the June-through-September rainy season falls between 96% and 104% of the average, then that is a normal or good monsoon.

Rainfall of less than 90% is considered a drought, rainfall of more than 110% of the average is considered an excess.

The department has been monitoring the moody monsoon for more than a century and over the years has had to repeatedly tweak its forecasting model and acquire new technology to better predict the rains. But its earliest predictions still leave a lot to be desired.

While the IMD allows for a wide margin of error of 5% above or below its April predictions, it still rarely gets it right.  Even within that 10 percentage point margin of error, its early prediction has been right in only six of the last 21 years.