Status and Plans for Operational Tropical Cyclone Forecasting and Warning Systems in the North Indian Ocean Region - Monitoring and Prediction of Tropical Cyclones in the Indian Ocean and Climate Change - page 149

Fig. 2: A typical example of observed and forecast track of depression which later on
became the very severe cyclonic storm, Thane.
forecast by IMD. The right hand side figure in Fig. 2 shows observed track of
cyclone, Thane. The comparison of forecast and observed track shows high
accuracy of track forecast by IMD.
The TC wind radii forecasts are generated in terms of the radii of 34 kts,
50 kts and 64 kts (1 kt = 0.52 ms -1 or 1.85 kmph) winds in four geographical
quadrants around the TC. These wind radii represent the maximum radial extent
of winds reaching 34 kts, 50 kts and 64 kts in each quadrant. The initial
estimation and forecast of the wind radii of TC is rather subjective and strongly
dependent on the data availability, climatology and analysis methods. The
subjectivity and reliance on climatology is amplified in NIO in the absence of
aircraft observations. However, recently with the advent of easily accessible
remote sensing derived surface and near-surface winds [e.g. Ocean Sat., Special
Sensor Microwave Imager (SSMI), low level atmospheric motion vectors and
Advanced Microwave Sounder Unit (AMSU)] and advances in real time data
analysis capabilities, IMD introduced TC wind radii monitoring and prediction
product in Oct., 2010. The initial wind radii estimates have become less
subjective due to the tools and products mentioned above. While better initial
estimates of 34, 50 and 64 knots radii are becoming available, forecasting
these wind radii remains a difficult task. It is mainly because of the fact that we
do not have any objective wind radii forecast methods and current NWP models
fail to produce forecasts that are better than climatology (Knaff et al., 2006;
Knabb et al., 2006).
The improvement in delivery services of cyclone warning is evident from
the fact that the time of delivery of cyclone warning bulletins to the disaster
managers has decreased over the years and is about 2.5 hrs. Due to all these
improvements in early warning services, the loss lives due to cyclone has
reduced significantly apart from other contributing factors like precyclone
preparedness, relief and rescue etc. by disaster management authorities.