A fresh weather-setting low-pressure area over north-west Bay of Bengal is pumping in monsoon easterlies from the Bay of Bengal into the plains and hills of North-West India.
Mercifully, there is no western disturbance coming in from the opposite direction, one of which had interacted with them and set up fatal torrents over Uttarkhand for three days last week.
Hills bound
The low-pressure area will seek to push into East-central and adjoining Central India but will likely get steered off course by seasonal westerlies (not associated with a western disturbance). It will head towards the hills of Uttar Pradesh and Bihar, and could set up rains along the Himalayan foothills bordering the State and even into Nepal for the next couple of days.
A western disturbance is a low-pressure wave emerging from Caspian Sea/Mediterranean and travels across Iran, Iraq, West Asia, Afghanistan and Pakistan before entering North-West India.It often carries a trough of low-pressure, carrying moisture picked along the way, and bangs it against the heights of Himalayas. The moisture gets lifted and cools to form clouds.
This triggers precipitation/fog depending on the season (summer/winter). When it interacts with moist monsoon easterlies from the Bay of Bengal, the rains can scale up several times over.
In the instant case, it is likely that the intensity of the monsoon flows triggered the formation of a ‘vortex,’ which is what believed to have sparked the Mumbai deluge way back in 2005.
Meanwhile on Sunday, the India Met Department warned that heavy rainfall (of 7-12 cm) could lash one or two places over flood-ravaged Uttarakhand over the next three days.
WEATHER ALERT
Heavy to very heavy rainfall is also likely over Arunachal Pradesh, Assam, Meghalaya, Nagaland, Manipur, Mizoram, Tripura, Odisha, Coastal Karnataka, Kerala and Lakshadweep during next two days.
Heavy rainfall would break out over Chhattisgarh, Vidarbha and north Andhra Pradesh during this period.
The seasonal trough was partly active across plains of North-West India and extending into East-central Bay of Bengal, signalling the activity heralded by the low-pressure area.
The offshore trough along the West Coast ran down from Maharashtra coast to Kerala coast, depicting active monsoon conditions in the region.