Here's a detailed analysis of south west monsoon onset prediction.
All GFS and other forecasts suggest that the monsoon will set in over southern India between 17-May-09 and 23-May-09.
Latest "water vapour" satellite shot suggests the stream of heavy water vapour has started moving in from South-west... this means that the south-west air current is also picking up.
Latest MJO predictions also coincide with the present predicted date of 20-May-09. Take a look at the WET phase moving in over southern India from 15-May-09.
Even the NCEP long range predictions also suggest a WET phase from 15-May-09 to 23-May-09.
We'll keep tracking the changes and will update this site... at this point of time the monsoon is tentatively predicted to set in over southern India on 20-May-09