Weather terms explained: India is headed into a summer of compounding extremes. A fresh Western Disturbance is set to bring unseasonal rain to the north, an El Niño year threatens a weak monsoon and intensified heatwaves, and the humidity is already making temperatures feel far worse than the thermometer reads. Western Disturbances are east-moving rain-bearing wind systems that originate beyond Afghanistan and Iran, and pick up moisture from the Mediterranean Sea, Black Sea, Caspian Sea and the Arabian Sea. These are typically extra-tropical cyclones resulting from low-pressure areas, formed by interactions between polar and tropical winds. Western Disturbances are embedded within the subtropical westerly jet stream, which is a high-altitude, fast-moving air current that flows from west to east in the Earth’s atmosphere. It is found over the Himalayan and Tibetan highlands.…