Extended Range Tropical Cyclone Predictions for East Coast of India - Monitoring and Prediction of Tropical Cyclones in the Indian Ocean and Climate Change - page 135

The processed outputs of model-ensembles and multi-model ensemble
(MME) predictions in the form of probabilistic forecasts of cyclogenesis and
cyclone tracks are made available online (for the NIO) by Climate Forecast
Applications Network (CFAN) (Belanger et al., 2012), and can be used as a
guideline for operational and disaster management related needs.
Methodology
CFAN's tropical cyclone forecast products provide extended range probabilistic
forecasts of individual storms and monthly outlooks of track density. While
CFAN's product development suite is most advanced for Atlantic tropical
cyclones, CFAN is also producing tropical cyclone forecasts for the North
Indian Ocean. CFAN's unique tropical cyclogenesis model has demonstrated
its skill 7-10 days in advance for tropical cyclogenesis in the North Indian
Ocean. CFAN's tropical cyclone forecast products include a sophisticated
analysis of the ECMWF Variable Ensemble Prediction System 1-15 days and
monthly forecast products that is integrated into a multi-model analysis with
forecasts from other global and regional models. The predictability of tropical
cyclones in the North Indian Ocean is evaluated using the ECMWF VarEPS
system. During the period 2007-10, VarEPS has undergone a number of
important changes that include increasing the horizontal and vertical resolutions
of the modelling system, expanding data assimilation procedures to include a
greater number of satellite radiance measurements, updating the model physics
(including cumulus convection parameterization schemes), and changing how
initial and stochastic perturbations are generated using singular vectors. VarEPS
includes the ECMWF global model that is run at TL1279 spectral truncation
(horizontal resolution; 16 km) with 91 vertical levels out to 10 days along with
51 ensemble members (50 perturbed members + one control run) at TL639
spectral truncation (horizontal resolution; 32 km) with 62 vertical levels.
Stochastic perturbations are also added during the model integration to account
for the uncertainty in parameterized physical processes. Five additional singular
vectors are computed and perturbed in the six grid spaces enclosing each TC
using a diabatic, adjoint version of the ECMWF global atmospheric model at
TL42 spectral truncation with 42 vertical levels.
Tropical cyclone tracking scheme to isolate tropical cyclones in the VarEPS
analysis and forecast fields, CFAN uses a modified version of the Suzuki-
Parker tracking scheme. To increase the intensity retrievals from VarEPS, 10-
m winds are replaced with winds averaged in the lower troposphere (10 m,
925 hPa, and 850 hPa). The tracking scheme processes each ensemble member
for tropical cyclones by first identifying candidate vortices that exhibit a local
minimum in mean sea level pressure. The component of the tracking scheme
confirms that each identified vortex possesses a warm core, as defined using
the Hart (2003) phase-space method. The cyclone phase analysis quantifies
the thermal structure by assessing the lower to middle troposphere's thickness