Geoscience Reference
In-Depth Information
4. Summary and Conclusions
The MME extended range forecast (2 to 3 weeks) based on coupled models
indicates very well the genesis of the system and associated rainfall distribution
due to the tropical cyclonic disturbances of post-monsoon seasons 2011. The
forecast for days 5-11 of dynamical parameters like the low-level vorticity,
low level circulation and the model rainfall clearly demonstrated the genesis
of the TC “Kaila” over the Arabian Sea during 28 Oct-04 Nov, 2011 and very
severe cyclone “Thane” over the Bay of Bengal during 25-30 December, 2011.
The 18 days forecast based on the initial condition of 27 October, 2011
valid till 13 November clearly indicated very active Arabian Sea and no
indication of genesis of any system over the Bay of Bengal till 13 November,
2011. The MME forecast weekly mean wind and weekly anomaly wind based
on 27 October initial condition and valid for days 5-11 (31 Oct-6 November)
and days 12-18 (November 7-13) indicated the formation of systems over the
Arabian Sea. Thus, an active Arabian Sea and inactive Bay of Bengal was very
much indicated in the MME forecast based on 27
th
October initial condition
and forecast valid for the period, 31 Oct-13 November, 2011. The genesis of
the very severe cyclone “Thane” was also indicated in week 1 (days 5-11)
MME forecast valid for the period from 19-25 December and its intensification
during the period 26 December-1 January, 2012.
Thus, the present generation coupled models are capable of providing useful
guidance in the extended range (1-2 weeks) for the tropical cyclogenesis
potential for about 15 to 18 days. However, more work is needed to define an
appropriate forecast genesis potential index to distinguish system developing
into TC and non-developing system (dissipated as depression) by considering
additional dynamical and thermo-dynamical parameters like wind shear,
convergence, middle tropospheric humidity and the phase and amplitude of
MJO etc.
Acknowledgements
The authors are thankful to the Director General of Meteorology for
encouragement and for providing all facility to carry out this study. The authors
are also thankful to the ECMWF and NCEP for providing the real time forecast
used for the preparation of cyclogenesis outlook in the extended range. Thanks
are also due to NASA for making the TRMM rainfall data available for this study.
REFERENCES
Belanger, James I., Curry, Judith A. and Webster, Peter J. (2010). Predictability of
North Atlantic Tropical Cyclone Activity on Intraseasonal Time Scales.
Mon. Wea.
Rev.
,
138:
4362-4374, doi: http://dx.doi.org/10.1175/2010MWR3460.1.
Search WWH ::
Custom Search