Overnight temperatures will rise with rain in the air as a western disturbance moves closer to northwest India.

The minimum temperature (night) has increased over Northwest India and adjoining East India in anticipation of the arrival of three consecutive western disturbances with moisture and clouds. However, parts of Bihar, isolated parts of East Uttar Pradesh, Jharkhand and West Bengal will have an overnight minimum with cooler and denser air below normal. The lowest temperature in the 24 hours ended Monday morning was 5.0 °C at Sabaur in Bihar, the India Meteorological Department (IMD) said. Incoming moisture filtering into the prevailing cold air will also cause heavy rain or snow in the Himalayas and dense to very dense fog in the plains during the next two to three days.

A welcome change in weather

This is a welcome change from the predominantly dry winter seen in North India so far. IMD predicts isolated heavy rain/snow over Kashmir on Tuesday and Wednesday; Himachal Pradesh on Wednesday and Thursday, in Uttarakhand on Wednesday; and on Friday in Arunachal Pradesh. In the plains, light to moderate isolated or scattered rain will occur over Punjab, Chandigarh, Haryana and Uttar Pradesh on Wednesday and Thursday. Isolated hail may occur over West Bengal and Sikkim hills on Wednesday and Friday.

Progeny circulations

A western disturbance is forecast in the short to medium forecast to trigger the development of a cyclonic circulation (if not more) over SW Rajasthan which would likely help sweep more moisture from the North Arabian Sea (near Gujarat). Western Disturbances, accompanied by a well-positioned descent over Rajasthan, are key to generating winter rains in northwest India, but have been conspicuous by their absence this winter.

Rainy week before?

International models believe that “three” western disturbances can bring varying amounts of rain over northwestern India and affect eastern India at least during the first week of February. A rain system may even descend along the east coast into east-central India and south-eastern peninsular India by mid-February. If it bears fruit, Odisha, Chhattisgarh, East Madhya Pradesh and Coastal Andhra Pradesh will benefit the most under these models.

Wet spell for East, South

Parts of Tamil Nadu, Karnataka and Telangana are also forecast to increase as the western disturbance moves eastwards and weakens southwards along the east coast and east of the Bay of Bengal. Initially, the prevailing anticyclonic circulation would sweep into the prevailing anticyclonic circulation, which would be replaced by southwesterly winds along the coast as the anticyclone retreats and moves into the central Gulf toward the end of the first week of February.

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