Abstract
Numerical simulations of four weak cyclonic storms [two cases of pre-monsoon cyclones: Laila (2010), Aila (2009) and two cases of post-monsoon cyclones: Jal (2010), SCS (2003)] are carried out using WRF-ARW mesoscale model. Betts-Miller-Janjic (BMJ) as cumulus parameterization (CP) scheme, Yonsei University(YSU) planetary boundary layer (PBL) scheme and WRF single moment 6 class (WSM6) microphysics (MP) scheme is kept same for all the cyclone cases. Three two-way interactive nested domains [60 km,20 kmand6.6 km] are used with initial and boundary conditions from NCEP Final Analysis data. The model integration is performed to evaluate the track, landfall time and position as well as intensity in terms of Central Sea Level Pressure (CSLP) and Maximum Surface Wind speed (MSW) of the storm. The track and landfall (time and position) of almost all cyclones are well predicted by the model (except for SCS cyclone case) which may be because of the accurate presentation of the steering flow by CP scheme. Irrespective of season, the intensity is overestimated in all the cases of cyclone, mainly because of the lower tropospheric and mid-tropospheric parameters are overestimated. YSU PBL scheme used here is responsible for the deep convection in and above PBL. Concentration of frozen hydrometeors at the mid-tropospheric levels and thus the latent heat released during auto conversion of hydrometeors is also responsible for overestimation of intensity.
Highlights
Tropical Cyclones (TCs) are among the most devastating weather systems on the Earth
In the case of cyclone Aila, the low pressure area (00UTC 22 May) is already formed and this initial condition is relatively closer to the Depression stage, so the well organized vortex with strong winds to the right side of the vortex (Figure 1(b)) is clearly depicted over 12 ̊N - 18 ̊N
The low pressure is already formed on 8 Dec and it took about 3 days to intensify into the depression
Summary
Tropical Cyclones (TCs) are among the most devastating weather systems on the Earth. They cause considerable damage and destruction to lives and property due to strong gale winds, torrential rain and associated storm surge. With the advancement in the computer technology, several simulation studies have been conducted to study the TCs over the NIO using high resolution mesoscale models (Pattanayak and Mohanty [6]; Deshpande et al [7] [8]; Trivedi et al [9]; Osuri et al [10] [11]; Bhaskar Rao et al [12]; Srinivas et al [13] [14]; Raju et al [15], Mukhopadhyay et al [16]) These studies are based on evaluating the model performance with respect to physics sensitivity, resolution, initial conditions and impact of data assimilation on the track and intensity forecast of very severe cyclones. In all the above studies, scientists have attempted simulation of strong tropical cyclones with rapid intensification There is another class of TC which does not reach the stage of very severe cyclonic storm but attains lesser intensity, named as weak cyclones [Sever Cyclonic Storms (SCS) and Cyclonic Storms (CS)]. We tried to find out the possible reason for the failure of this combination for the track of SCS cyclone
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