Momentum budget analysis of maintenance of Arabian Sea tropical cyclone Ockhi

Abstract

In this study an effort is done to explain the maintenance of the  Very Severe Cyclonic Storm(VSCS) Ockhi using the angular momentum(AM) budget technique . The  AM budget  equation  for a region bounded by ,  to   and  to   in  (x,y,p,t) co-ordinate system is used from an earlier study.  The different terms are explained with relative importance.  This technique is used to  the diagnosis of different small, medium and large weather systems by several authors.  The Very Severe Cyclonic Storm(VSCS) Ockhi –a rare situation in Arabian Sea – is studied  with a reanalyzed dataset   in a fine mesh width. The values of different terms in the AM budget equation are calculated for  pressure levels-1000,800,500,200,100hpa’s and for four day periods viz. 30 Nov ,01 Dec ,02 Dec  and 03 Dec 2017    .The AM budget was prepared for the eight  observation time periods of 00, 03,06,09,12,15,18,21 UTC  for each day.  The area selected is 5.04N - 19.2N, 60E- 77E where VSCS TC Ockhi formed.The sink and source terms are compared  and the results  are correlated with the help of charts .  The NCMRWF IMDAA data set is used and the results are depicted in charts and  results are compared  with the observed synoptic behavior of the   system . Keywords: -  Angular Momentum Budget,  Equation, Source/Sink terms,                            VSCS  Ockhi-Diagnosis