The accurate prediction of warm-season convective systems, and the heavy rainfall and severe weather associated with them, remains a challenge for numerical weather prediction models. This study looks at one such circumstance in which back-building convection forms perpendicular to, and above the cold pool region behind strong bow echoes. We refer to this phenomenon as a "bow and arrow" because, on radar imagery, the two convective lines resemble an archer's bow and arrow. The "arrow" can extend over hundreds of kilometers and can cause damage from high winds, hail and flooding. Events of this nature pose a particular challenge to forecast because they require an accurate forecast of the earlier convection and the effects of that convection on the environment. In this study, radar and surface observations of four events are presented to identify common environmental conditions prior to the development of the back-building convection. Additionally, simulations of three cases using the Weather Research and Forecasting (WRF) model are analyzed in an attempt to understand the mechanisms responsible for initiating and maintaining the convective line. Due to coarse resolution, observational analyses are only useful for inspection of the synoptic-scale. Model output from numerical simulations is utilized to examine the mesoscale in the vicinity of the convective arrow. Several environmental characteristics are evident in each of the studied cases. Strong southwesterly flow (inducing warm air advection and gradual isentropic lifting), in addition to directional and speed convergence into the convective arrow region possibly contribute to convection initiation. Horizontal wind speed shear and increased wind speed in the area surrounding the arrow may be associated with the linear orientation of the arrow. It seems as though when these ingredients are combined with thermodynamic instability, there is a greater possibility of formation and maintenance of a convective arrow behind a bow echo.

Around Sri Lanka and to the south of India sea surface temperatures (SST) are cooler compared to the surrounding region during summer monsoon. This region where SSTs are relatively cooler is known as the cold pool. Owing to its possible impact on monsoon variability, some studies have been carried out to understand the evolution of cold pool SST during this period. These studies suggest, coastal upwelling along southern coast of Sri Lanka and eastward advection of cooler water contributes to the decrease in SST during summer monsoon. However, the processes leading to the formation of cold pool, still, remain unknown. In this study, we have investigated the mechanism responsible for the formation and maintenance of southern Bay of Bengal (BOB) cold pool using high resolution satellite data, model simulations and in-situ observations for the year 2009. Our study reveals formation of cold pool is dominated by atmospheric processes, whereas oceanic processes dominate its maintenance. Cooling of SSTs during premonsoon and onset phase acts as a prerequisites for the formation of cold pool, which are linked to the reduction in Net Heat flux (NHFX) during theses periods. The changes in NHFX during premonsoon and onset phase are dominated by reduction in Short-wave (SW) radiation associated with strong convective activity over cold pool. Convective activity over the cold pool are associated with the northward movement of Maximum Cloud Zone (MCZ) that forms over Equatorial Indian Ocean (EIO) during these periods. SST within the cold pool after the steady increase during February-April months, cools first during premonsoon rain event and then during monsoon onset. Analysis of high resolution satellite data for the period 2003-2009 suggest that, these sequence of events occurs with minor amount of inter-annual variability. Lead-lag correlation also made it clear that SST response in 5 days to the corresponding variation in atmospheric processes. SST within the cold pool shows several intraseasonal cooling events during the summer mon-soon. Considering that rainfall above the cold pool is very low during the summer monsoon, these cooling events occurring within the summer should be necessary for maintaining the cold pool. The seasonal evolution of SST shows that it continues to decrease till the end of the summer monsoon. In-situ data collected during CTCZ field program in 2009, at two time series locations (TSL) and model simulations were used to determine the processes responsible for such cooling events. To estimate the contribution from advection to the observed SST tendency at fixed location, a measurement stratergy called ‘opertaion advection’ was used in this study. This stratergy involves measurement of oceanographic parameters along four edges from TSL directod along North, South, East and West for estimation of horizontal temperature gradients. Our results from SST cooling events captured by CTD at two fixed locations suggests that horizontal advection and entrainment dominate the SST evolution. Model temperature equation evaluated near the TSLs are convinient with the observations and suggest that atmospheric forcing is not responsible for intraseasonal cooling events.