Why Did North India Witness Rain In April? Will May 2023 Be Cool Too? Know What An Expert Says

Rainfall was witnessed over several regions of the country, including North India, in early April 2023. As a result, the temperatures were low during the pre-monsoon season compared to last year.

In early April 2023, several regions of India, including northern India, witnessed rainfall and cool temperatures. An expert tells ABP Live the reasons behind this.

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India, especially the northern regions of the country, witnessed a cooler April this year, compared to 2022. Rainfall was witnessed over several regions of the country, including North India, in early April 2023. 

From March 1 to April 12, the departure of the all-India cumulative rainfall from the long average period rainfall was over 19 per cent. This means that the rainfall during the pre-monsoon season was 19 per cent greater than the normal rainfall that occurs during this period, calculated on the basis of the long average period. 

However, subdued rainfall activities were observed over most parts of the country from April 9 to April 12, as a result of which India witnessed a rise in day temperatures, according to the Indian Meteorological Department (IMD). 

In a statement dated April 15, 2023, the IMD said that maximum temperatures over northwest India could gradually decrease by about two to four degrees Celsius after April 17. 

From April 17 to 19, light to moderate scattered rainfall with thunderstorms and lightning are likely over Delhi, Uttar Pradesh and West Rajasthan. In the western Himalayan region, hailstorms and isolated heavy rainfall are possible.

Why North India Witnessed Rainfall In April

North India witnessed rainfall in April due to western disturbances, Dr Vivek Gupta, Assistant Professor, IIT Mandi, told ABP Live.

“The rainfall in April is generally attributed to western disturbances. These disturbances originate in the Mediterranean region and bring precipitation to North India between October and April each year. Depending on their intensity, duration and location, western disturbances can result in rain, snowfall, cold waves, and even flash floods in the region,” Dr Gupta said.

Why Was April Cool This Year? Will April Be Cool In Future Years As Well?

Western disturbances were responsible for the relatively lower temperatures witnessed early April this year. However, Dr Gupta said that these weather patterns are not restricted to this year alone.

“The temperature in April can vary from year to year, depending on the development of atmospheric systems. Some years may be colder, while others may be warmer,” Dr Gupta explained.

How IMD Made Its Forecast Of Heat Waves From March To May

The IMD had predicted a heatwave from March to May, especially in the northern and central parts of India. However, heat wave conditions were witnessed in some parts of India only after April 12. Before that, the temperatures were relatively cool. 

So, a question arises about how the IMD forecast was made. 

According to Dr Gupta, even small disturbances in one location impact the weather in another region, because the atmosphere is a highly chaotic system. Dr Gupta explained that climate and weather models may have limited computational power, due to which the physics used in them are simplified. Also, models are sensitive, due to which minor variations in initial conditions significantly change the forecast. Since variations in atmospheric conditions can occur at any point of time and unprecedentedly, models do not always correctly predict the upcoming weather conditions.

“The atmosphere is a highly chaotic system, where even small disturbances in one location can significantly impact the weather in another. Weather forecasts are generated using complex mathematical equations that represent the physics of meteorological systems. These equations form what is known as a weather or atmospheric model. These models require immense computational power and are typically run on supercomputers. The accuracy of the forecasts produced by these models depends on numerous factors such as initial conditions, grid resolution, the physics used in the model, and lead time. Due to the sensitivity of these models, even minor variations in initial conditions can result in significant changes in the forecast. This creates uncertainty in the final forecast. Additionally, due to limited computational power, the physics used in these models must be simplified, which further increases uncertainty in the forecasts,” Dr Gupta explained.

Since the IMD makes forecasts by calculating the average of different forecasts obtained by running the same weather model multiple times with slightly different initial conditions, the resulting forecasts often vary significantly, according to Dr Gupta.

“When the same weather model is run multiple times with slightly different initial conditions, the resulting forecasts can vary significantly. As the forecast lead time increases, the uncertainty in the model’s predictions also increases. So which forecast is correct? The one showing higher temperatures or the one showing lower temperatures? The truth is that all of the forecasts are possible and none of them can be considered fully correct. One way to summarise these forecasts is to calculate their average, which would represent all of the model runs better. The IMD employs a similar methodology to make its forecasts. However, there are countless factors that impact weather conditions. While western disturbances may have caused lower temperatures for a few days, if the models have shown warmer temperatures overall, it is reasonable to expect warmer temperatures,” Dr Gupta said.

Are These Changing Weather Patterns Related To Climate Change?

Several studies on climate change have reported changes in the seasonality of India's weather patterns. However, Dr Gupta said, it is difficult to determine with certainty whether the current anomalies in the weather system are due to inter-annual variations or a long-term shift caused by climate change.

“The impact of climate change can only be confirmed if a trend continues for 30 years,” Dr Gupta said.

Will There Be Rain In May As Well? Will May Be Cool Like April?

While western disturbances resulted in lower temperatures in early April, it cannot be said with certainty whether May also will be cool, according to Dr Gupta.

"We have to look for the IMD forecasts. However, in no way, I would expect May to be cool," Dr Gupta said.