Delhi, UP See Monsoon Pause. When Will Rain Return?

July began with relentless downpours, bringing much-needed relief from the blistering summer heat. However, after a dramatic spell, the monsoon appears to have suddenly lost momentum across northwest India, including Delhi-NCR and parts of Uttar Pradesh. Dense rain clouds have given way to clear skies, humidity levels have fluctuated, and temperatures have begun climbing once again.

Why has the monsoon slowed down?

Experts say the primary driver behind the current dry spell is a meteorological phenomenon known as a "break monsoon" condition, coupled with a significant shift in monsoon trough.

In the context of Indian weather, a trough is an elongated region of low atmospheric pressure. It is represented on weather maps as a dashed line and typically brings heavy clouds, moisture, and rainfall as it forces warm, moist air to rise. The IMD primarily tracks two major types of troughs that influence Indian weather, namely the monsoon trough and the offshore trough. 

The shifting monsoon trough

Per experts, the monsoon trough which essentially is a low-pressure belt stretching across the country acts as a highway for rain bearing winds, has now migrated away from the plains of northwest India.

M Danish, scientist at IMD Lucknow, said, "The monsoon belt shifted to the Terai belt in the northern part of Uttar Pradesh. So, due to that, only northern portion is experiencing rainfall". 

Speaking on the slowdown of the monsoon, he added, "The slowdown means shifting of the monsoon trough. One low-pressure system was formed last week, so it's shifting in the northern part. Due to that, the monsoon trough is also shifted."

Due to the northward shift toward the Himalayan foothills, the rainfall has been concentrated in the Northern parts of UP such as Gorakhpur, Balrampur, and Kushinagar and East India, leaving Delhi-NCR and Western UP dry.

Break monsoon conditions and dry winds

The primary driver behind the current dry spell is a meteorological phenomenon known as a break monsoon condition, coupled with a significant shift in the monsoon trough.

Adding to this shift, weather patterns have entered a classic "break" state. 

Mahesh Palawat, vice-president of Meteorology and Climate Change at Skymet Weather, explains how this alters the wind and humidity profiles of the region. "For the past few days, the weather across Northwest India, including Delhi, has remained completely dry... The reason behind this is that a break monsoon condition has set in," he said.

Explaining the phenomenon, Palawat added, "A break monsoon condition occurs when the axis of the monsoon trough shifts into the Himalayan foothills. Consequently, the winds south of the trough blow from the west. Because these are dry winds, humidity levels drop sharply. This drop in humidity causes the rain to stop, stops cloud formation, and triggers a rise in temperatures."

While the northwest may be seeing dry spells, the eastern and northeastern parts of the country are experiencing heavy flows. Palawat points to multiple cyclonic circulations over northeast Bihar, Bangladesh, and Northeast Assam which are pulling all the moisture from the Bay of Bengal into those regions.

An unusually long break: the El Nino factor

While a monsoon break is usually a normal seasonal occurrence, this dry spell is turning out to be far longer than typical breaks, which usually last between 4 to 6 days. Experts point to larger global climate concepts to explain the prolonged dry spell.

Palawat notes, "This break monsoon condition typically happens once or twice in July and August, usually lasting for 4 to 5 days, or 6 days at most. However, this time we are looking at an unusually prolonged break of 11 to 12 days. We can attribute this to the effect of El Nino, which has now started becoming dominant, its impact is explicitly visible in the second half of July."

This shift has rapidly impacted India's overall cumulative rainfall statistics. Palawat adds, "By July 9, strong rains had brought the monsoon deficit down to just 12 per cent. However, within a span of just three days, this deficiency has climbed back up to 18 per cent. We will have to wait and see what form the monsoon takes then, but as of right now, a clear El Nino impact is visible."

When will rain return to Delhi-NCR and UP?

The good news, however, is the fact that this break is only temporary. The IMD as well as even private forecasters say the monsoon trough will eventually migrate back southward and usher in a revival of rainfall across the dry terrain. 

According to the IMD, heavy rainfall is likely to continue over parts of northwest, east and northeast India during the next three to four days. Delhi is likely to remain under partly cloudy skies on Tuesday, with no significant rainfall forecast

M Danish (IMD Lucknow) expects the weather systems to gradually slide down. "Whatever the trough line at the northern part of the belt, now it's started moving southward. So now, what I think we can say, is the revival of the monsoon."

Skymet's Mahesh Palawat provides a clearer timeline for when the national capital and neighboring states will see widespread relief. "Once this axis of the monsoon trough begins moving southwards after July 20, rainfall activity is expected to pick up again. So, we can safely say there is a one-week break right now, after which rain will restart across Punjab, Haryana, Delhi, and Western Uttar Pradesh, causing temperatures to slide down once more."

Residents in Delhi-NCR and Western UP will need to prep for warm, humid, and largely dry days for now. However,  the good news is that relief is on the way as the monsoon axis prepares to journey southward in the final ten days of the month.