NEWS Bulletin from Indian Society For Sustainable Agriculture And Rural Development
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South-West Monsson rains is very important for Indian agriculture. The four-month season usually begins from June. Global Climate Change has begun impacting weather across the globe. Frequency of El Nino and La Nina events has increased causing its impact on the rains. Frequency of natural disasters, too, has increased. In this, context, monsoon forecasts assume importance-----
1. First monsoon trend is positive, La Nina means good rains
2. Good rains expected in SW Monsoon: IMD
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In THE INDIAN EXPRESS - Front Page - April 15, 2008
First monsoon trend is positive, La Nina means good rains
ASHOK B SHARMA
Posted online: Tuesday, April 15, 2008 at 0040 hrs
NEW DELHI, APRIL 14: Ahead of this week's official April forecast for the monsoon by the India Meteorology Department (IMD), the US-based International Research Institute for Climate and Society (IRI) has said there is hope for good rains in the first half of the four-month monsoon season beginning June. The rainfall intensity may taper off in the last two months of the season.
The IRI map shows that in the first two months of the monsoon season, there will be good rains in the southern peninsula and parts of central India. In August-September, apart from peninsular India, there will be good rains in Gujarat and parts of Rajasthan and in the plains of the eastern Himalayas.
There is only a distant possibility of the spoilsport El Nino (warming of the Pacific water above normal) emerging in the period in the Nino 3.4 region — the region in the Pacific which influences Indian monsoons. In fact, the IRI sees the presence of the opposite phenomena La Nina (cooling of the Pacific waters below normal). Historically, La Nina causes good rains.
But La Nina is on a weakening trend. According to IRI, the 85% to 75% probability of La Nina in April and May would come down to 60% to 50% in June, the first month of the monsoon season. In July, the probability estimate remains in the range of 50% to 40%. In September, the last month of the monsoon season, the probability of La Nina would come down to 35% to 30%. But the El Nino factor is seen low at 5% to 20% in the monsoon period, while neutral condition could range from 5% to a maximum 50%.
Given the gradual decline of the La Nina factor, the good rains in the first two months of the monsoon season may taper off towards the end. There is also a possibility of early arrival on the southwest monsoon, sometime in May due to the higher influence of the La Nina factor. The IRI is slated to update its forecast on April 17.
But the US-based Climate Prediction Center (CPC) of the National Centers for Environmental Prediction (NCEP), confirming the gradual decline of the La Nino factor, said: "La Nina is expected to continue for the next three months... Nino 3.4 region indicate La Nina will become weak and persist through May-June-July 2008." La Nina has already caused heavy rainfall over Indonesia.
According to IRI, western equatorial Indian Ocean has below normal temperatures while the eastern part has temperatures above the normal. The below normal temperature conditions in western Indian Ocean is likely to weaken slowly.
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Good rains expected in SW Monsoon: IMD
ASHOK B SHARMA
Posted online: Wednesday, April 16, 2008 at 1918 hrs IST
New Delhi, April 16: The official weather forecasting agency, India Meteorological Department (IMD) has said that the countrywide rainfall in the four-month monsoon season, beginning June would be 99% of the long period average (LPA) rainfall for the period which is 89 cm.
The forecast is subjected to a model error of +/-5%.
Making this initial forecast for the South-West Monsoon, IMD said that it would be "near normal" rainfall as it has revised its categorization of rainfall basing on 1901-2005 data. In the revised categorization there is no normal rainfall. Rainfall in the range of 96% to 104% of the LPA is termed near normal, that in the range of 90% to 96% of the LPA is termed below norm and that below 90% of the LPA is termed deficient.
Rainfall in the range of in the range of 104% to 110% of the LPA is termed above normal and that above 110% is termed excess.
The Union Minister for Science and Technology and Earth Sciences, Kapil Sibal releasing the forecast said, "the presence of La Nina factor (cooling of Pacific waters below normal) would boost the prospects of good monsoon rains. The recent global dynamical and statistical models say that La Nina will become weak but persist for the next three months."
The Indian Express and The Financial Express on April 15 quoting IRI data had said La Nina would cause good rains in the first two months.
Sibal said that IMD while making its forecast had taken help of both statistical and dynamical models. The dynamical models works well for peninsular India and northeastern region.
The leader of the monsoon forecast team, M Rajeevan said that a set of 5 predictors were used for making this initial forecast like North Atlantic sea surface temperature in December and January, equatorial southeast Indian Ocean temperature in Feberuary and March, east Asia mean sea level pressure in February and March, north-west Europe land surface air temperature in January and equatorial Pacific warm water volume in February and March.
The IMD would consider another set of 6 predictors while making the final forecast for the season in June. In May the IMD would predict the date of arrival of the South-West Monsoon at the Kerala coast.
Global climate change and its impact on Indian weather and monsoons is the issue which Indian meteorologists are exploring to understand. In last March there was unusual heavy rains in the four southern states – Andhra Pradesh, Karnataka, Kerala and Tamil Nadu, causing damage to the standing crops. In Tamil Nadu the rainfall was in excess of 801%, that in Kerala in excess of 469%, that in Karnataka in excess of 1666% and that in Andhra Pradesh in excess of 811%. This year's March rainfall was a all time high record in Tamil Nadu, Karnakata and Kerala since 1875, while in Andhra Pradesh it was the second highest since 1875.
There was practically no winter rains over north and northwest India in 2007-08, but there was a sudden spurt of heavy rains and thundershowers in the region on April 4, 2008 leading to cloudy weather for the next three days. In past there has been cases of sudden spurt in day temperatures in early February causing damage to wheat crop....
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