Kolkata’s monsoon withdrawal is drawing closer as a depression over coastal Myanmar and adjoining parts of the Bay of Bengal moves north-northwestwards and weakens, with the system unlikely to bring any significant impact to Bengal, according to a Met report cited by The Telegraph.
The depression was located around 90km southeast of Minbu in Myanmar on Tuesday morning. The report said the system was expected to weaken into a well-marked low-pressure area over coastal Myanmar, adjoining southeast Bangladesh and the northeast Bay of Bengal during the following 24 hours.
It was then likely to continue moving towards southeast Bangladesh and adjoining areas of Myanmar, Mizoram, Tripura and the northeast Bay of Bengal while weakening gradually. The system’s movement is being watched because its eventual dissipation will help weather scientists assess whether Bengal could receive another significant spell of rain before the monsoon ends.
Kolkata remained rainless for the third consecutive day on Tuesday. The city continued to feel hot, although the air was noticeably drier than it had been a few days earlier. A Met official in Kolkata attributed the change to dry northwesterly winds being drawn towards Bengal by the system.
The official said the winds were coming from northwestern India, where the southwest monsoon had already retreated. Once the depression dissipates, the weather parameters over Bengal are expected to become clearer, allowing the Met office to assess the remaining monsoon conditions.
An extended-range forecast issued by the Met office on September 24, covering the two weeks from September 25, said conditions would become favourable for the withdrawal of the southwest monsoon from the remaining parts of northwest India and adjoining central and east India during the second week, between October 1 and 7.
Weather scientists generally consider three to four rain-free days one of the conditions required before announcing the withdrawal of the southwest monsoon. A decline in atmospheric moisture is another indicator. The most significant marker is a reversal in wind direction, with winds from north India replacing the moisture-bearing flow from the Bay of Bengal.
The withdrawal of the monsoon changes Kolkata’s weather pattern in practical ways. As winds from the Bay gradually stop flowing into the city, humidity begins to fall even when daytime temperatures remain high. The Met official said Tuesday’s conditions were typical of the end of September and that the weather would change gradually.
Kolkata recorded a maximum temperature of 33.2 degrees Celsius on Tuesday, although it felt hotter when the sun was bright. The usual date for the southwest monsoon’s retreat from south Bengal is around October 10. The monsoon withdrawal line had reached Uttar Pradesh by Tuesday, according to the Met office.
The timing of the final withdrawal remains dependent on the next few days of rainfall, moisture levels and wind patterns. The monsoon left Bengal on October 13 last year, while the current system near Myanmar is expected to weaken before the Met office makes a clearer assessment of the season’s final spell.
