- Unusual linear 1,000-km rain band western disturbance causes rain from Afghanistan through Pakistan to India
- Widespread thunderstorms, hail, and gusty winds affect northwest India and southern states
- Moisture source includes the Mediterranean, Caspian, Black seas, and Arabian Sea amplification
An unusual weather phenomenon is unfolding across parts of India, Pakistan, and Afghanistan - bringing intense rainfall, thunderstorms, gusty winds, and even hailstorms in a month that usually kickstarts summer heat. The rare event stands out not just in its timing, but also in its formation and shape.
The phenomenon brings a perfectly linear low-pressure western disturbance extending a 1,000 kilometre rain band from Afghanistan through Pakistan and deep into India. Usually, western disturbances are extratropical cyclones originating from Mediterranean lows, curving northeast and peaking in winter to bring snowfall and cold waves. In contrast, the current one is a straight trough, with weather patterns increasingly growing unpredictable lately.
Photo Credit: X.com/allindiaweather
The active western disturbance, an upper-air cyclonic circulation over northern Pakistan is driving widespread thunderstorms, gusty winds (40-80 kmph), isolated hailstorms, and light-to-moderate rainfall or snowfall across northwest India. It has already triggered heavy to very heavy rain in the sub-Himalayan West Bengal and Sikkim, heavy showers in south Karnataka, Andhra Pradesh, Kerala, and Tamil Nadu, and hailstorms in multiple states.
The current western disturbance features a trough aloft in the middle and upper westerlies. This trough interacts with multiple lower-tropospheric cyclonic circulations over north Madhya Pradesh, east Uttar Pradesh, west Rajasthan, Haryana, northeast Assam, coastal Andhra, and interior Tamil Nadu-Kerala.
The western disturbance will sustain activity through today in the Western Himalayas and adjoining plains, with a reduction thereafter.
However, a fresh, feeble western disturbance is approaching from March 22.
What is the moisture source?
The core moisture for the unusual western disturbance originates from evaporation over the Mediterranean, Caspian, Black, and Persian Gulf seas.
During its eastward transit over the Middle East, the Arabian Sea amplifies the moisture content upon the Himalayan orographic lift. Current troughs over Gujarat-Mannar and cyclonic features enhance low-level convergence, fueling intense outbursts.
Delhi-NCR forecast
Delhi and its adjoining National Capital Region (NCR) can expect light-to-moderate rain with thunderstorms and winds of 30-50 kmph until Friday, with maximum temperatures of 25-28 degrees Celsius, significantly below normal.
Why are late-March rains rare?
Climatologically, India sees four to six intense western disturbances per month between December to February (16-24 total per year). Activity tapers sharply by late March as the jet stream weakens and shifts northward, making large systems rare (1-2 per year historically).
Recent trends, however, show lengthening seasons and increasing frequency into April, linked to stronger subtropical jets delaying retreat and broader climate variability.
