The Hindu Business Line : Is Konkan belt next on the hit list?

THE deluge in Mumbai on Tuesday that saw a record breaking 94.4 cm of rain swamp the international airport and the neighbourhood has been attributed to the formation of a monsoon vortex, a destructive feature associated with the most active phase of the monsoon.

July normally brings good precipitation to the country's financial capital, but Tuesday's inundation was of a scale unprecedented in the history of urban India. The highest rainfall recorded in Mumbai till now was 37.5 cm on July 5, 1974.

Speaking to Business Line, Dr Akhilesh Gupta, Director of the National Centre for Medium Range Weather Forecasting (NCMRWF), said monsoon vortices are strong, circular-moving and comparatively short-lived systems embedded in the prevailing monsoon trough. But they can trigger a cloudburst within an area, extending to as much as 30 km.

In meteorological parlance, these are tiny components of a very strong and elaborate monsoon system. They are very unpredictable and mostly escape the notice of the best weather models.

Vortices are formed when the strength of the westerlies blasting into the natural barrier offered by the Western Ghats in the Konkan belt does not allow them to align along the elongated offshore trough and instead, cause them to rotate around their own axis with such intensity as to trigger a drencher.

The stronger the westerlies, the more intensively active will be the vortex and the more destructive will be its impact. According to Dr Gupta, the Konkan belt might not have seen the last of the vortices yet, given the strength of the prevailing monsoonal flows. Unfortunately, there is no way of predicting when and where they can take shape.

For instance, it was one of these offshore vortices that had dumped rain in parts of Goa two days back, he said.

In any case, the ongoing rain activity in and around Mumbai would continue for some more days but not in the same intensity.

The reason is that the dynamics associated with the atmosphere do not allow for the sustenance of vortices of such forceful motion beyond 24 hours. On Wednesday, the low-pressure area was positioned over east Madhya Pradesh and the neighbourhood.

This means that the rain activity would now get shifted to the north Konkan region and south Gujarat over the next few days.

Gujarat can expect to get heavy rain from the west-northwest orientation of the `low' and the circulation pattern over the north east Arabian Sea, which has not yet evolved into a full-scale mid-tropospheric cyclone.South east Rajasthan can also hope for some good showers over the next few days.

The offshore trough running from the Konkan belt to Karnataka is likely to persist for the next 2-3 days and the ongoing widespread rainfall activity over the north Konkan region and South Gujarat region is likely to continue.

Fairly widespread rainfall activity is likely over coastal Karnataka, north Interior Karnataka, Telangana and coastal Andhra Pradesh.

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