Rainfall based warning is displayed at the top of this homepage whenever the effective rainfall (12-hour half value rainfall) at any rainfall station exceeds the corresponding threshold as shown in the figure on the left.

Definition of half value rainfall:

Effective Rainfall value(12-hour half value rainfall) is used to statistically predict disasters due to long time continuous rainfall. It is similar to cumulative rainfall, however each hourly rainfall is assumed to reduce by half in 12-hour time.