Pune: The onset of southwest monsoon over Kerala has become increasingly uncertain as weather experts point to weak monsoon winds and unfavourable large-scale weather patterns, raising doubts over its arrival by the normal June 1 date.India Meteorological Department (IMD) had earlier projected monsoon onset over Kerala around May 26, with a model error of plus or minus four days. Recent weather bulletins, however, have not specifically iterated that timeline, while continuing to state that conditions remain favourable for further advance of monsoon into parts of the Arabian Sea and the Bay of Bengal.An IMD official said the department’s position remains unchanged for now. “Conditions are being monitored. As and when there is an update, we will mention it,” the official said. Asked about experts suggesting a later onset, the official said IMD’s forecast window of May 26 plus-minus four days remained in place.Independent experts, however, say the atmospheric picture has become more complex over the last few days.GP Sharma, president of Skymet, said current weather patterns over Kerala resembled pre-monsoon activity rather than a sustained monsoon setup and suggested the onset could overshoot the normal date.“As of now, typical criteria for onset of monsoon over Kerala is difficult to be met during the next one week. Rainfall currently seen over Kerala appears more localised and pre-monsoonal in nature, rather than the broad and stable rain pattern usually associated with monsoon onset,” he said.Akshay Deoras, research scientist from the National Centre for Atmospheric Science and Department of Meteorology, University of Reading, United Kingdom, said rainfall alone could not determine monsoon onset and warned that key atmospheric ingredients remain missing.“For the onset of monsoon to be officially declared over Kerala, three parameters are crucial: rainfall, sufficiently deep monsoon winds over the Indian Ocean and cloud patterns,” he said.While Kerala and Lakshadweep received substantial rain on May 24, Deoras said monsoon winds over the Indian Ocean remain weak and have not yet reached Kerala. He said, “Forecasts from several models, including the one used by IMD, do not indicate any significant strengthening of these winds until at least May 31. Any declaration of monsoon onset before then would therefore lack scientific basis.”Deoras added that forecasts currently do not provide a clear signal on the exact onset date in early June. He said, “This uncertainty stems from large-scale atmospheric conditions that influence the monsoon and are expected to remain unfavourable through the first fortnight of June.”Independent weather expert Abhijit Modak said, as per the latest weather model analysis, monsoon onset uncertainty over Kerala still continues. “Currently, the low-level westerly flow appears somewhat disorganised, and the atmosphere is in a wait-and-watch phase regarding the next proper monsoon alignment. The fresh upper-air circulation over the Arabian Sea is now projected to move away from the Kerala coast, which may temporarily weaken the organised moisture transport required for a sustained monsoon onset,” he said.“Based on the current model guidance, it appears that Kerala may have to wait until around June 1, with plus or minus two days’ model error, for a more favourable and sustainable monsoon onset set-up to develop,” Modak said. ”The normal date for monsoon onset over Kerala is June 1.
