Question

what are the western disturbances ?

Answer 1

western disturbance is the term used to describe an extratropical storm that brings sudden winter rain to the northwestern parts of indian subcontinent.

Answer 2

Western Disturbance (WD) is the term used to describe an extratropical storm that brings sudden winter rain and snow to the northwestern parts of the Indian subcontinent. This is a non-monsoonal precipitation pattern driven by the Westerlies.
                                               or
a low pressure area or a trough over surface or the upper-air in the westerly winds regime, north of 20°N, causing changes in pressure, wind pattern and temperature fields. It is accompanied by cloudiness, with or without precipitation.