Language of weather forecasting has been changed by IMD for improve communication Gap


The language of weather forecasting has been changed by the India Meteorological Department (IMD). And they also have re-defined terms which are not scientifically detailed in weather forecasting. For that IMD has given official notification, in order to avoid communication gap with the civil administration so that they can be more genuine in future weather measures.

Following are the changes:

Classification all-India rainfall into five categories:

  • Normal: ± 10 % of the long period average (lpa).
  • Below normal: Rainfall lowers than 10 % below average of the lpa.
  • Above normal: Rainfall greater than 10 % above average of the lpa.
  • Deficient year: Rainfall deficit between 10 and 20 % up to 40 % of India’s spatial area.
  • Large deficient year: Rainfall deficit of over 10 % across more than 40 % of India’s area.

Criteria to classify seasonal rainfall

The rules have been changed to classify seasonal rainfall and it includes new 6 new categories in the place of old four rainfall categories (excess, normal, deficient and scanty).

  • Large excess: 60 % and above.
  • Excess: between 20 % and 59 per cent.
  • Normal: minus 19 % to plus 19 per cent;
  • Deficient: minus 20 % to minus 59 per cent.
  • Large deficient: below 60%
  • No Rain: 0%.

IMD also has standardized key terms

  • Heat wave: Temperatures is above usual temperatures for the region (greater than 4.5 degree C).
  • Severe heat wave: Temperatures is greater than or equal to 47 degree C.
  • Cold wave: Temperatures is less than 4.5 degree C above usual temperatures for the region.
  • Severe cold wave: Minimum temperature is 2 degree C or lower.

- Published/Last Modified on: January 13, 2016