Seasonal forecasting of tropical cyclogenesis over

Authors: D R PATTANAIK M MOHAPATRA

Publish Date: 2016/03/18

Volume: 125, Issue: 2, Pages: 231-250

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Abstract

Over the North Indian Ocean NIO and particularly over the Bay of Bengal BoB the postmonsoon season from October to December OND are known to produce tropical cyclones which cause damage to life and property over India and many neighbouring countries The variability of frequency of cyclonic disturbances CDs during OND season is found to be associated with variability of previous largescale features during monsoon season from June to September which is used to develop seasonal forecast model of CDs frequency over the BoB and NIO based on principal component regression PCR Six dynamical/thermodynamical parameters during previous June–August viz i sea surface temperature SST over the equatorial central Pacific ii sea level pressure SLP over the southeastern equatorial Indian Ocean iii meridional wind over the eastern equatorial Indian Ocean at 850 hPa iv strength of upper level easterly v strength of monsoon westerly over North Indian Ocean at 850 hPa and vi SST over the northwest Pacific having significant and stable relationship with CDs over BoB in subsequent OND season are used in PCR model for a training period of 40 years 1971–2010 and the latest four years 2011–2014 are used for validation The PCR model indicates highly significant correlation coefficient of 077 076 between forecast and observed frequency of CD over the BoB NIO for the whole period of 44 years and is associated with the root mean square error and mean absolute error ≤ 1 CD With respect to the category forecast of CD frequency over BoB and NIO the Hit score is found to be about 63 and the Relative Operating Curves ROC for above and below normal forecast is found to be having much better forecast skill than the climatology The PCR model performs very well particularly for the above and below normal CD year over the BoB and the NIO during the test period from 2011 to 2014The author is very much grateful to the Director General of Meteorology and Deputy Director General of Meteorology NWP India Meteorological Department for providing all the facilities to carry out this work Thanks are due to IRI USA for making the CPT available to us which was used in our study and particularly to Dr Simon Mason IRI USA for useful discussion on CPT Thanks are also due to the NCEP for providing the reanalysis data used in the present study and the anonymous reviewers for useful comments to improve the quality of the paper

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