Slow winds, clear skies: What’s behind Delhi’s unusually cool October?

Context: With the approaching winter, minimum temperatures in the national capital have trended downward over the last one week.

How is the weather changing in Delhi?

• Delhi is in the phase of seasonal transition between the southwest monsoon, which has withdrawn from the country, and winter.

What is causing the cooler weather in Delhi?

• The weather is dry and the sky is mostly clear over North and Northwest India. Gentle northwesterly winds are blowing over the region.
• Western disturbance developed as a trough at mid-tropospheric level, but did not significantly influence the local weather.

Western disturbance

• A western disturbance is an extra-tropical storm originating in the Mediterranean region that brings sudden winter rain to the northwestern parts of the Indian subcontinent.
• It is a non-monsoonal precipitation pattern driven by the westerlies.
• The moisture in these storms usually originates over the Mediterranean Sea, the Caspian Sea and the Black Sea.
• Extratropical storms are a global phenomena 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 disturbances are more frequent and strong in winter season.
• Western disturbances are important for the development of the rabi crop, which includes the locally important staple wheat.

https://indianexpress.com/article/explained/delhi-cool-weather-october-slow-winds-clear-skies-6910631/