This study deals with the life cycle of bow echo events on October 24 and 26-27, 2006, from Doppler weather radar (DWR) observations supported by Radiosonde and National Centers for Environmental Prediction (NCEP). The cell bow echo (CBE) on October 24 evolved from two small isolated cells with radar reflectivity ≥40？dBZ. The vertical structure consists of one single mature cell with 20？dBZ echoes reaching up to 10？km while 40？dBZ echoes extended uniformly from ground to ～5？km height. The radial velocity shows a high value >？15？m/s towards the radar at the upper height (about 6 to 11？km); the lower height is predominant with velocity away from the radar (about 5 to 15？m/s). The squall line bow echo on October 26 and 27 has its origin over ocean and moved towards the radar site and decayed thereafter. The radar reflectivity pattern for this squall line showed it to be a trailing stratiform type squall line with length of ～200？km. The echo top height was more than 12？km in height. Strong inflow cases were observed from both radiosonde and radar. 1. Introduction The life cycle of mesoscale convective systems (MCSs) can be studied with the help of on-board IR and microwave sensors as well as ground based Doppler weather radar (DWR) . Though the geostationary IR data is very useful for the study of evolution of MCSs because of its large areal coverage, it can give only the cloud top information but unable to give details inside of the system. On the other hand, DWR can give much better information of the MCS but their coverage is limited, where the reliable observation >200？km is restricted due to the refraction of the transmitted signal. The passive microwave radiometer cannot be used for the study of the evolution of MCSs as these are carried by polar satellite with low repetition. A multisensor approach is useful approach to study the multifaceted characteristics of MCSs. Till date many of the studies of MCSs are performed with the help of both active and passive sensors: evolution (e.g., [2–6]), size and structure [7, 8], and reflectivity structures (e.g., [9–12]). The severe weather events are mostly associated with the organized MCSs such as bow echoes and squall lines. Bow echoes were named and described in detail by Fujita . A bow echo is defined as a nontransient bow or crescent shaped radar signature with a high reflectivity gradient on the convex edge. Most of the time, they are associated with severe weather. According to Fujita  the bow echo commonly evolves from either a single convective cell or a line of cells. Klimowsky et al.
M. A. LeMone, E. J. Zipser, and S. B. Trier, “The role of environmental shear and thermodynamic conditions in determining the structure and evolution of mesoscale convective systems during TOGA COARE,” Journal of the Atmospheric Sciences, vol. 55, no. 23, pp. 3493–3518, 1998.
J.-J. Wang, “Evolution and structure of the mesoscale convection and its environment: a case study during the early onset of the southeast Asian summer monsoon,” Monthly Weather Review, vol. 132, no. 5, pp. 1104–1120, 2004.
J.-J. Wang and L. D. Carey, “The development and structure of an oceanic squall-line system during the South China Sea Monsoon Experiment,” Monthly Weather Review, vol. 133, no. 6, pp. 1544–1561, 2005.
J.-J. Wang, X. Li, and L. D. Carey, “Evolution, structure, cloud microphysical, and surface rainfall processes of monsoon convection during the South China Sea monsoon experiment,” Journal of the Atmospheric Sciences, vol. 64, no. 2, pp. 360–380, 2007.
M. I. Biggerstaff and R. A. Houze Jr., “Kinematics and microphysics of the transition zone of the 10-11 June 1985 squall line,” Journal of the Atmospheric Sciences, vol. 50, no. 18, pp. 3091–3110, 1993.
D. P. Jorgensen, M. A. LeMone, and S. B. Trier, “Structure and evolution of the 22 February 1993 TOGA COARE squall line: aircraft observations of precipitation, circulation, and surface energy fluxes,” Journal of the Atmospheric Sciences, vol. 54, no. 15, pp. 1961–1985, 1997.
S. Businger, T. Birchard Jr., K. Kodama, P. A. Jendrowski, and J.-J. Wang, “A bow echo and severe weather associated with a kona low in Hawaii,” Weather and Forecasting, vol. 13, no. 3, pp. 576–591, 1998.
R. W. Przybylinski and D. M. DeCaire, “Radar signatures associated with the derecho. One type of mesoscale convective system,” in Proceedings of the 14th Conference On Severe Local Storms, pp. 228–231, American Meteor Society, Indianapolis, Ind, USA, 1985.
K. R. Knupp, B. Geerts, and S. J. Goodman, “Analysis of a small, vigorous mesoscale convective system in a low-shear environment. Part I: formation, radar echo structure, and lightning behavior,” Monthly Weather Review, vol. 126, no. 7, pp. 1812–1858, 1998.
D. J. Musil, A. J. Heymsfield, and P. L. Smith, “Microphysical characteristics of a well-developed weak echo region in a High Plains supercell thunderstorm,” Journal of Climate & Applied Meteorology, vol. 25, no. 7, pp. 1037–1051, 1986.