PUNE: Monsoon on Thursday missed Skymet's May 26 onset date over Kerala and is most unlikely to arrive over the coastal state even on May 27 (Friday), as suggested by the India Meteorological Department (IMD) in its forecast earlier this month.
A senior IMD official told TOI that though monsoon would not make an onset over Kerala on Friday, the top weather body had issued the May 27 onset forecast with a model error of plus or minus four days.
"We would be coming up with the exact likely date of monsoon onset over Kerala soon. On Thursday, just 33% of the stations in Kerala reported significant rainfall. That is a major issue why the onset over Kerala cannot be declared on Friday. Convection seems to be increasing over places like Lakshadweep, but over Kerala, rainfall has not been significant lately. Other onset criteria over Kerala have already taken place. We are, however, still monitoring the rainfall over the coastal state."
The top weather forecaster officially declares monsoon onset over Kerala when around 60% of the available weather stations in the coastal state record rainfall of 2.5mm or more for two consecutive days after May 10.
IMD on Thursday said conditions were likely to become favourable for monsoon onset over Kerala "during the week".
IITM scientist Roxy Mathew Koll said, "The latest extended range forecast by IMD indicates below-normal monsoon rainfall and its delayed progress for the next two weeks. This is not a good sign to look forward to for regions that have already been affected by severe rain deficit and heatwaves during March-May period this year."
Koll said cross-equatorial flow of monsoon winds seemed quite strong just south of India, but it does not seem to be intensifying further north, which would have aided monsoon progression over land in the coming days. "Most rainfall activity currently seems to be concentrated over the Arabian Sea and not over land areas," he said.
GP Sharma, president, Skymet Weather Services, told TOI, "Monsoon missed the May 26 onset date over Kerala predicted by us earlier. Numerical weather models failed us this time as the current monsoon situation could not be predicted. Forecasts were clearly indicating that the onset was supposed to happen well before time this year, as had been predicted by all experts concerned. However, we feel that the Indian Ocean Dipole (IOD) index, which has become more negative over the past fortnight, seems to have been responsible for weakening the monsoon even while it was expected to advance. Negative IOD is not good for the Indian monsoon."
Sharma said along with other onset criteria, nine stations in Kerala were required to receive more than 2.5mm rain for two consecutive days after May 10 to herald monsoon's arrival over Indian mainland. "This number stood at five during the last 24 hours ending Thursday," he said.
On what went wrong with monsoon advance recently, Sharma said, "Both the monsoon arms, Arabian sea and Bay of Bengal, should be acting in tandem and reinforcing each other, pushing the monsoon flow forward. For this to happen, we need some good weather systems to aid the rainfall. These systems don't seem to be forming as of now."
