An active Western Disturbance (WD) has struck most parts of north and central Pakistan. This WD has caused widespread rain and isolated snow over the region. The WD started affecting Pakistan from the 13th and continued till the 15th of this month. Its induced low pressure area formed over south Pakistan and adjoining Rajasthan on 13th March with a cyclonic circulation extending up to 1.5 km. This WD moved eastwards from Iran, across Afghanistan & Pakistan. These systems are likely to move into western Himalayas in next 24 hours.
Western Disturbances together with induced cyclonic circulations are frequent during winters and are responsible for precipitation over the region to a large extent. This year, frequencies of these WDs have increased, thus resulting in more spells of rain. Usually, WDs are active over a region only for one or two days. WDs originate in the Caspian Sea or the Mediterranean Sea as extra-tropical cyclones. They gradually travel across the middle-east from Iran, Afghanistan and Pakistan to enter the Indian sub-continent. WDs move from west to east. Dr R.M. Saxena, Professional Meteorologist at Skymet weather division defines Western Disturbance as “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.”
These two systems caused widespread rain & isolated snow over North & central Pakistan. The chief amount of rainfall received during last 24 hours is as follows:-
