Find in Library

ABSTRACT: India Meteorological Department (IMD) introduced cone of uncertainty (COU) in cyclonic disturbances (CDs) alongwith the 72 hr track forecast over the north India Ocean (NIO) in 2009. The track forecast for CDs is issued for +6, +12, +18, +24, +36, +48, +60 and +72 hrs time period from the stage of deep depression onwards. An attempt is made to evaluate COU forecast issued by IMD during 2009-2011(3 years). The size of the cone is deduced from climatological track forecast errors. The accuracy of COU forecast has been analysed with respect to basin of formation, season of formation, intensity and type of track (climatological/straight moving and recurving/looping type) of CDs by calculating percentage of total number of forecasts in each category lying within COU.The observed track lies within the forecast COU in about 60% of the cases over the NIO. The accuracy of COU forecast is about 66% in post-monsoon season and about 50% in pre-monsoon season. The observed track lies within the forecast COU in 90% cases of climatological/straight moving CDs and 39% cases of recurving/ looping CDs. The observed track lies within COU forecast in about 71% cases of severe cyclonic storm and 37% cases of cyclonic storm/deep depression. Keywords: Tropical cyclone, North Indian Ocean, Cone of uncertainty, Track