|
The onset of Monsoon over Kerala may be delayed by a week-the new likely date being June 7, 2005, with a forecast error of plus or minus three days. The forecast is based on the new statistical model developed by the India Meteorological Department with 6 predictors to forecast the onset of Monsoon over Kerala. These predictors are: NW India Minimum Temperature, Pre-monsoon rainfall peak over south Peninsula, Outgoing Long wave radiation (OLR) anomaly over Indo-China region, South Indian Ocean Sea Surface Temperature, South Indian Ocean lower tropospheric wind, and Outgoing Long wave radiation (OLR) anomaly over South-west Pacific region. This statistical model has a forecast error of ± 3 days.
There is no one to one correspondence between monsoon onset date over Kerala and subsequent performance of south-west monsoon during the season (June to September) over the country as a whole. In spite of the expected delay in monsoon onset over Kerala, the 2005 south-west monsoon seasonal rainfall over the country as a whole is expected to be near normal as given in the IMD’s first forecast issued on 20 April, 2005.
Over the Indian mainland, monsoon arrives by 1st June over south Kerala. Slowly moving northwards along the western coast and northwestwards across central India, monsoon covers the whole India by 15th July. The onset date over Kerala has a standard deviation of about 7 days. During the last 50 years, the earliest monsoon onset over Kerala was on 14th May in 1960 and the most delayed onset was on 18 June in 1972.
On 20th April 2005, the India Meteorological Department (IMD) had issued the long range forecast for the 2005 south-west monsoon season rainfall as 98% of the Long Period Average (LPA) with a model error of ± 5 %.
EL NINO
During the second half of 2004, weak El Nino conditions prevailed over the equatorial Pacific Ocean, which started in the first week of July 2004. From early December 2004, cooling trend has been observed over this region suggesting a transition to ENSO-neutral conditions. However during April 2005, surface temperatures increased again in the eastern equatorial Pacific associated with the arrival of an oceanic wave. The effects of this present warming along the west coast of South America are expected to be brief.
A majority of the statistical and coupled model forecasts indicate that ENSO-neutral conditions will prevail during the northern summer (June-August) of 2005.
SRK
|
