Western disturbances

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Western Disturbance: A Weather Phenomenon of North India recurs

A new Western Disturbance (WD) has arrived in northern India, with authorities predicting a reasonable amount of rain and snowfall at higher elevations.

Western Disturbance is a weather phenomenon that affects North India during the winter months. It is a low-pressure area that forms over the Mediterranean Sea and moves eastwards, affecting the weather conditions of the Indian subcontinent.

Essential Facts:

Origin: Western Disturbance originates over the Mediterranean Sea, mainly during the months of November to March. The jet streams in the upper atmosphere play a crucial role in its formation and movement.

Effect on Weather: Western Disturbance brings rainfall, snowfall, and hailstorm in North India. The intensity of the rainfall varies from light to heavy, and the amount of snowfall depends on the altitude and temperature of the region. The higher the altitude, the more significant the snowfall.

Regions Affected: The Western Himalayan region of North India, including Jammu and Kashmir, Himachal Pradesh, Uttarakhand, and parts of Punjab, Haryana, and Delhi, are primarily affected by Western Disturbance.

Impact on Agriculture: Western Disturbance has both positive and negative impacts on agriculture. While the rainfall and snowfall brought by it are beneficial for Rabi crops and groundwater recharge, the hailstorms can cause significant damage to standing crops.

Monitoring and Forecasting: The Indian Meteorological Department (IMD) monitors and forecasts the movement and impact of Western Disturbance. The IMD issues alerts and warnings to the concerned authorities to take necessary actions to mitigate the impact of the weather phenomenon.

Pin It
Whatsapp

Western Disturbance: A Weather Phenomenon of North India recurs

A new Western Disturbance (WD) has arrived in northern India, with authorities predicting a reasonable amount of rain and snowfall at higher elevations.

Western Disturbance is a weather phenomenon that affects North India during the winter months. It is a low-pressure area that forms over the Mediterranean Sea and moves eastwards, affecting the weather conditions of the Indian subcontinent.

Essential Facts:

Origin: Western Disturbance originates over the Mediterranean Sea, mainly during the months of November to March. The jet streams in the upper atmosphere play a crucial role in its formation and movement.

Effect on Weather: Western Disturbance brings rainfall, snowfall, and hailstorm in North India. The intensity of the rainfall varies from light to heavy, and the amount of snowfall depends on the altitude and temperature of the region. The higher the altitude, the more significant the snowfall.

Regions Affected: The Western Himalayan region of North India, including Jammu and Kashmir, Himachal Pradesh, Uttarakhand, and parts of Punjab, Haryana, and Delhi, are primarily affected by Western Disturbance.

Impact on Agriculture: Western Disturbance has both positive and negative impacts on agriculture. While the rainfall and snowfall brought by it are beneficial for Rabi crops and groundwater recharge, the hailstorms can cause significant damage to standing crops.

Monitoring and Forecasting: The Indian Meteorological Department (IMD) monitors and forecasts the movement and impact of Western Disturbance. The IMD issues alerts and warnings to the concerned authorities to take necessary actions to mitigate the impact of the weather phenomenon.

2021

5-Feb-2021: Several studies conducted by various scientific institutes in the country in regard to the impact of western disturbances during winter season on Indian climate

Impact of Western Disturbances

There are several studies conducted by various scientific institutes in the country in regard to the impact of western disturbances during winter season on Indian climate. The studies show that;

  • 30% of annual precipitation over North West Indian region (J & K, Ladakh, Himachal Pradesh &Uttarakhand) is received during winter and it is mostly associated with Western Disturbances. It also causes rainfall over the adjoining places of north India.
  • Precipitation associated with Western Disturbances (WDs) influences Himalayan climate, glaciers, snow-water storage, flora, fauna, agricultural crops and human inhabitants etc.

The adverse weather elements associated with Western Disturbances are;

  • Intense precipitation in the form of snow, rain or hail leading to landslides, avalanches and damage of agriculture and manmade structures.
  • Dense to very dense fog events leading to interruption in aviation / rail / road transport services.
  • Cold Wave to Severe Cold Wave and Cold Day to Severe Cold Day conditions after the passage of western disturbances.

However, precipitation from the western disturbances is very vital for the Rabi Crop over northwest India. Also snowfall/snowmelt in the Hilly regions contribute to river flow and drinking water for people living downstream.

  • India Meteorological Department (IMD) issues forecast & warnings for the weather elements related to WD also. From National Weather Forecasting Centre (NWFC), IMD forecasts are given in sub- divisional scale whereas the Regional Weather Forecasting Centre (RWFC) and State Weather Forecasting Centre (SWFC) issue forecast and warnings in district level and station level.

In addition to these, a Forecast Demonstration Project (FDP) for winter weather systems has been initiated from 2016 and it has brought together several institutes other than IMD to enhance the monitoring and forecast of weather elements related to WD. Accordingly a FDP bulletin is prepared and issued daily during November to February when the Western Disturbances are more active.

From November 2020 onwards, IMD started issuing a special bulletin related to winter weather systems (All India Multi-hazard Winter Warning Bulletin) which provides colour coded warning for five days for the adverse weather elements associated with WD, along with present weather scenario.

IMD started issuing Impact Based Forecast (IBF) in the recent past. Impact Based Warning contains guidelines to the general public while getting exposed to the severe weather. These guidelines are finalized by NDMA (National Disaster Management Authority) in coordination with IMD and the same is being issued for the adverse weather elements related with WD.

2019

18-Apr-2019: The western disturbance brings heavy rainfall across various parts of the country.

What is Western Disturbance?

It is an extratropical storm originating in the Mediterranean region that brings sudden winter rain to the north-western parts of the Indian sub-continent. It is a non-monsoonal precipitation pattern driven by the westerlies.

Extratropical storms are a global phenomenon with moisture usually carried in the upper atmosphere, unlike their tropical counterparts where the moisture is carried in the lower atmosphere. In the case of the Indian subcontinent, moisture is sometimes shed as rain when the storm system encounters the Himalayas.

Western Disturbance originates in the Mediterranean Sea as extra-tropical cyclones. A high-pressure area over Ukraine and neighbourhood consolidates, causing the intrusion of cold air from Polar Regions towards an area of relatively warmer air with high moisture. This generates favourable conditions for cyclogenesis in the upper atmosphere, which promotes the formation of an eastward-moving extratropical depression. They gradually travel across the middle-east from Iran, Afghanistan and Pakistan to enter the Indian sub-continent.

Impact:

  • It plays important role in bringing moderate to heavy rain in low-lying areas and heavy snow to mountainous areas of the Indian Subcontinent.
  • This disturbance is usually associated with cloudy sky, higher night temperatures and unusual rain. This precipitation has great importance in agriculture, particularly for the Rabi crops. Wheat among them is one of the most important crops, which helps to meet India’s food security.
  • Excessive precipitation due to this disturbance can cause crop damage, landslides, floods and avalanches. Over the Indo-Gangetic plains, it occasionally bring cold wave conditions and dense fog. These conditions remain stable until disturbed by another western disturbance. When western disturbances move across northwest India before the onset of monsoon, a temporary advancement of monsoon current appears over the region.