IMD predicts heavy to very heavy rain over Western Himalayan region over next 3-4 days

Vibha Sharma

Chandigarh, August 19  

It is not over yet. The IMD has predicted more rains for the two weather-battered hill states—Uttarakhand and Himachal Pradesh—in northwest India over the next “three-four days”.

In fact, the weather office on Saturday forecast heavy to very heavy rains till August 22 in several parts of the country, along with heavy falls in east and adjoining central India (August 18-19) and increase in activity over northeast from August 20.

In north, the weather office forecast “light/moderate scattered to fairly widespread rain/thunderstorm and lightning with isolated heavy rain over Himachal Pradesh and Uttarakhand in the next five days, over west Uttar Pradesh till August 22 and over east Uttar Pradesh on August 22 and 23”.

“Isolated very heavy rain is also likely over Uttarakhand till August 23 and over Himachal Pradesh till August 21,” it added.

Basically, heavy rain has been predicted over Western Himalayan Region and adjoining plains from August 20 and an orange alert for very heavy rains issued for Arunachal Pradesh and Uttarakhand for August 21 and 22.

Monsoon trough to move eastwards from August 21

Currently, the monsoon trough is running along normal position and passes through Ganganagar, Narnaul, Datia, Satna, the centre of Low Pressure Area over north Chhattisgarh and neighbourhood, Keonjhargarh, Balasore and thence southeastwards to Northeast Bay of Bengal and extends up to 1.5 km above mean sea level.

Its eastern end is expected to shift northwards to the north of its normal position from August 21, the IMD said.

According to experts, the recent spell of heavy rain in the two hill states was caused due to northward movement of the axis of the monsoon trough, making weather conditions favourable for heavy to very heavy rains across the Himalayas which have been facing the brunt of climate-induced change in weather patterns since the beginning of the 2023 monsoon season.

According to experts, weather conditions may have been favourable for heavy rains, but climate change has a definite role in the increasing intensity, causing flash floods and landslides.

In view of the unprecedented damage to life and property, the Himachal Pradesh government has declared the state as a “natural calamity- affected area”.

Double whammy—humidity and temperature

All this when the country is witnessing “break-monsoon conditions”, say experts, however, the climate change has been causing  higher temperature and increased humidity.

Its effects on southwest monsoon are becoming evident by every passing year, they add.

Normally during this phase, the axis of the monsoon trough shifts northwards and stays stationed over the Himalayas triggering heavy to very heavy rains over the hilly region. However, the warming atmosphere has increased the intensity of rain tremendously.

An increase in the warming means more energy in the environment, leading to more rain.

There has been an increase in the average relative humidity across India because of the rapid rise in land and sea temperatures.

2023 monsoon apt example of climate change 

According to Mahesh Palawat of Skymet Weather, the 2023 monsoon is an “apt reflection of what climate change impacts would do to the

Himalayas if global warming goes unchecked”.

“The warmer it becomes, the more moisture the atmosphere can hold. Higher temperatures lead to more water being evaporated from the earth’s surface. This increases the holding capacity of the air, resulting in more droplets and heavier rain, sometimes in a shorter space of time and over a smaller area.

According to the Clausius-Clapeyron equation, the air can generally hold around 7% more moisture for every 1-degree Celsius temperature rise, say experts, adding that humidity is the prime factor behind the increasing likelihood of heavier rains and even more dangerous heat waves.

Changing monsoon patterns and WDs

There has also been a change in the western disturbance (WD) trajectory.

Experts say WDs are more prevalent during winter when they travel in lower latitudes, bringing rain and snow over north India. During the summer, these systems tend to travel in higher latitudes and do not have much impact on the region during the ongoing season. However, active WDs have travelled across the Himalayas during the monsoon season.

According to the IPCC’s 6th Assessment Cycle Report, warming in the Himalayas has increased with altitude.

There has also been a steep rise in land subsidence incidents during the past couple of years.

The experts say the Himalayan range, particularly the one in Uttarakhand, is very sensitive to extreme rainfall events, given the nature of the mountains.