Extreme weather, monsoon and forecasting

Prelims and Mains

The river stood at or above its highest recorded level at Patna and Bhagalpur in September 2026 while the State's rain since 1 June ran 27 per cent below normal, which is possible because the water that floods a plain need not have fallen on it.

• September rain was 31 per cent above normal and fell in heavy local spells.
• Water released from Nepal was not the main cause, so the fix is basin wide rather than bilateral.
• Embankments cut rivers off from their floodplains.
• Many people live on diara, the low riverine tracts that lie within the river's reach.

See also: Farakka Barrage

Prelims and Mains

A forecast becomes a warning only when something watches a storm as it builds, and in the hills the terrain works against the instrument that does.

• A Doppler Weather Radar sends out a microwave pulse and reads the echo returned by raindrops, snow and hail, which tells it where precipitation is and how heavy it is.
• The Doppler effect in that echo also gives the speed at which those drops are moving, so the radar reads the wind inside a cloud and not only the rain falling out of it.
• Because it scans again every few minutes it follows a storm or a cloudburst as it develops, which is what turns a forecast into a warning.
• A radar beam travels in a straight line, so a ridge standing in front of it blocks the beam and the valley behind that ridge goes unwatched, which is beam blockage.
• Siting in the hills is a trade-off: a radar placed high sees over more ridges, but its beam then passes above the low cloud that is dropping the rain.
• A cloudburst builds and empties within the hour, so a gap in cover is not a slow loss of accuracy but a warning that never comes.
• Himachal Pradesh was sanctioned two more radars, taking the hill State from three to five, with the Union government funding them.
• The State's case was for cover that the existing three cannot give.

See also: Mission Mausam